Friday, February 19, 2021

Getting Ready for Stiltgrass 2021

My battle against Japanese stiltgrass, Microstegium vimineum, is a nearly year round effort.  To help me focus my efforts I’ve prepared the following table to remind me of where I will get the most for each hour of work in each season.

Japanese Stiltgrass Control






Late Winter Early Spring

Pre-emergent treatment

Effective in lawns and smoother (even) surfaces with access to soil surface.  Allows lawns and perennials to get a head start.

Will affect all germinating seeds for several months.  Uneven coverage on rough surfaces.  Application needs to be at the right time.

Takes at least 2 years to knock down seed bank to see significant progress.  More time to complete elimination, if ever. 

Late spring-Summer


Grass selective herbicide leaves broad leaf plants and some sedges intact. Try products containing Fluazifop-p-butyl 

Difficult to control collateral damage, especially with non-selective herbicides

Targeted application and use of selective materials may limit side effects.

Late spring-Summer


Non-toxic and selective.  Opens space for other species.

Labor intensive; left over stilt grass will expand to fill gaps.

If removal is not complete this will need to be repeated at the end of summer

Late summer/Early fall

Cutting/ pulling/ burning

All methods to reduce the amount of seed

Need to complete actions before seed begins to ripen.

Copious amounts of seed being produced, need to be thorough and avoid spreading any ripened seed.

 Because Japanese stiltgrass is an annual there are two points of vulnerability based on its life cycle.  As an annual all plants start new from seed each spring.  If you can disrupt germination you can make a significant dent in how much stiltgrass you will have to deal with.  This is where I have found preemergent herbicides to be very useful.  Products labeled for control of crabgrass have proven effective.  The other weak spot is seed production in early fall.  More on that below.

On the left you can see the effect of a single treatment with
a preemergent crabgrass herbicide.  The right side is thick with
bright green Japanese stiltgrass.  Photo taken in early July.

An important part of using a preemergent is getting it applied at the proper time, neither too early or too late in the spring.  There are tools on the internet that track growing degree days, such as GDD Tracker 4.0.  The idea is that plants will develop at a rate controlled by how much heat they receive over time.  For germination, the soil temperature is particularly important.  It is important to realize with a preemergent it is critical to have the material well distributed on the soil prior to the onset of germination.  That’s why I like a really like the calculator, it builds in the time when you should actually apply the product.  Another way to time the application is to watch for when forsythia are in bloom.  In my limited experience just before peak bloom is a good time to do the preemergent application.

I have found that preemergent use on the lawn is very effective.  There was a significant reduction in stiltgrass in the lawn after treatment for two consecutive years.  Also the red fescue that I overseeded is really starting to knit together.  I should do a test this year to see if I can skip treating a portion of the lawn for a year without a resurgence of stiltgrass?  Maybe for a small area.  I'd hate to lose the progress I've made so far.

I have also experimented with preemergent treatments in a meadow area.  Here the ground is much coarser and there is a lot of debris on the ground.  It is very difficult to get an even application of the granular herbicide.  I have seen a decrease in the amount of stiltgrass seedlings in areas where the preemergent was applied.  But there are also patches where the stiltgrass still comes in densely.  I assume that these are due to uneven application.    

Another concern I have with this meadow area is that the preemergent treatments will inhibit the germination of other desirable plants.  The meadow area I have is dominated by wingstem (Verbesina alternifolia), wild blackberry, smartweed and a variety of sedges.  In addition there are the usual invasives: Wineberry (Rubus phoenicolasius), Oriental bittersweet, Japanese honeysuckle and multiflora rose.  Besides reducing the amount of Japanese stiltgrass I have also noticed a significant reduction in the amount of bull thistle, Cirsium vulgare, a non-native species.  (Of course having a thick layer of JSG will also inhibit or kill anything that is not well established, so one needs to balance the effects of the herbicide with not doing anything.)  Last spring I transplanted in a number of black- and brown-eyed Susans (Rudbeckia hirta and R. triloba) and some wild bergamot (Monarda fistulosa) in the gaps that opened up.  It is particularly important for the ‘Susans’ that they be allowed to reseed.  For this year (2021) I will not do the preemergent treatment in the areas with these reseeding perennials.  Instead I will focus on some areas that have not been treated before.

Last year I did experiment with surface burning of stiltgrass seedlings.  While it did provide some temporary control, more seedlings appeared a week or two later.  For me burning with a torch is a maintenance activity and it’s easier than bending over to pick out seedlings.  Spring fire does not work as a one-time treatment in my hands.


I have been reading more about grass specific herbicides and how they would fit into a plan for eliminating Japanese stiltgrass.  I can see using them as a tool in maintaining a perennial bed or in a well defined, designed landscape.  For me I don’t expect to be using them because most of my landscape is more like managed wildlands.  I generally welcome any native species that pops up annual, perennial, shrub or grass.  So I don't want to run the risk of killing something new and unexpected.

This patch of unmown grass has benefited from both regular pulling
of stiltgrass and a single treatment with a preemergent. 
As I've opened spaces I've planted in natives such as switch grass
and wild bergamot (taller plants to the back right).  The yellow flowers
are wingstem and goldenrods that have come in naturally.

Most of my mid-season activity is focused on pulling and back-filling with desirable, native species.  This year I will be moving many of my excess plants from the vegetable garden, Rudbeckias and Monarda, as well as some overgrown New England asters and goldenrods into spots where I will have weeded out the stiltgrass.  Native species that are competing well against stiltgrass include golden ragwort, mayapple, wild bergamot and grasses and sedges such as river oats, deertongue grass, Virginia wild oats, and rosey and sallow sedges (Carex rosea and C. lurida).


This patch of golden ragwort, seen here in mid-April, started from a
single clump planted 2 years earlier.  This species is very effective
at excluding both Japanese stiltgrass and garlic mustard.

6 years ago I seeded in Virginia wild rye.  It is particularly evident
in unmown, shady areas around trees.  This cool season grass gets
started early in the season, well before stiltgrass, and grows 2-4 feet tall.

If pulling is not complete, the remaining stiltgrass will refill newly created voids.  One thing I learned last year was that it can put down roots anywhere a node comes in contact with the soil.  I will try to limit my efforts on mid-season pulling and burning to when I have something to fill back into the open space or where there are new natives trying to get established.  I will store up my energy for late summer when there is less time for the stiltgrass to regenerate and have enough energy to produce flowers and seeds.

Late Summer and Fall

This is a time when you can make a significant dent in the amount of seed that is produced for next year with the least effort.  Pulling stiltgrass that is 3+ feet tall in late summer will remove a huge amount of potential seed.  It’s also easier on the back than pulling shorter plants.  Timing is important.  It should be done early enough that any seed present on the plants will not be able to mature and late enough that and remaining fragments of plants won’t have time to recover and put up additional flowers.  Here in the mid-Atlantic August is about the right time for that. 

If you find yourself pulling stiltgrass later in the season after seeds have started to form you will need to be more careful about disposing the pulled grass.  You don’t want to risk spreading any seed around.  While I knew that stiltgrass has flowers hidden within the stem, I had not realized until last year that there may be flower stalks buried in nearly every leaf node of a healthy stiltgrass stem.  That is a lot of potential seed!

By my index finger you can see one of the flower spikes
 that was hidden within the stem.  These are able to
self pollinate and produce seed without ever opening up.

Cutting or mowing close to ground level is most effective at this time, too.  Burning with a torch at ground level (when safe and where allowed) is also effective.  I’m not certain, but there is a possibility that some cuttings or unburned stem parts may reroot if they contact the soil under favorable conditions.  I will often rake up the cuttings and put them in a separate pile where they can decompose without mixing in with other materials.

In years past I have spent a lot of time in the late summer and early fall raking stiltgrass out of the lawn.  This was probably of little use since much of the stiltgrass had probably developed seed by then.  Last year I combined raking with overseeding with cool season turf grasses.  The hope was that the cool season grasses would germinate quickly and fill in the gaps left from the stiltgrass.  That should work, in theory, but I can't comment on the results.

So the plans are in place and it's almost time to get started!

Thursday, January 21, 2021

Plans for 2021

The New Year brings new opportunities for trying new things in the garden as well as continuing projects from last year. 

One project that I will be continuing from last year is removing and replacing vinca from a wooded area.   I will be expanding that to begin removing yellow archangel, Lamiastrum galeobdolon, from an adjacent area.  While this species is not currently on any official state invasive plant lists in the Mid-Atlantic, it is a species of concern.  (It is a state listed invasive in Washington State.  More locally it is on the Arlington County Virginia invasive plant list.)  It does spread aggressively by runners and root fragments.  Pulling is effective as long as all of the plant is removed.  I sprayed some of it with glyphosate last fall when doing garlic mustard treatments, but I don’t know if that will be effective.  Triclopyr is reported to be effective.

I really love the round leaflets of the trefoil and the way winds
its way along to ground, finding openings. 
 In addition to the plants added last year to replace the vinca, this year there will be some white wood aster, Eurybia divaricata, and round-leaved ticktrefoil, Desmodium rotundifolium.  Both of the species are well adapted for growing in dry, partly shady locations.  While the aster is fairly easy to come by I have been searching for the ticktrefoil ever since I first saw it in the wild back in 2005.  I’ve got a lead on it at a not-too-far-away nursery and hope to secure a few plants for this year.  The name trefoil refers to its having three leaves.  This particular species is notable for its distinctly round leaves.  An other common name is prostrate ticktrefoil, for its ground-hugging habit.  This makes a good partner in a matrix planting.  I can see using it around upright perennials like Solomon's seals and clumping ferns.

Virginia waterleaf has deeply incised leaves with whitish splotches
 that resemble water spots.  The plants shown here are in a moist
shady area near the Potomac River.  Other plants in this area include
Virginia bluebells, trilliums and bedstraw.  Photo taken early late April.

Another invasive that I have been fighting for a while and making some headway is Japanese stiltgrass, Microstegium vimineum.  I will continue fighting it with a multipronged assault, including preemergent herbicides and lots of pulling.  As I’m opening up space I’m backfilling with native species.  In addition to more of the Obedient Plant, Physostegia virginiana, that I put in last fall I‘ll be adding some Virginia waterleaf, Hydrophyllum virginianium, to a moist shady area.  This area is already populated by Virginia bluebells, Mertensia virginiana, lady fern, Athyrium filix-femina, and a variety of grasses and sedges.  (In writing this I wonder if I should look into creating a display garden of plants with only the specific epithet of virgini--.  Talk about being a plant nerd.)

The foliage on this NJ tea looks an awful lot like many Japanese spireas. 
Its compact size and tight clusters of white flowers in mid-summer
makes an excellent replacement for exotic Spireas.
While looking over the property it dawned on me that I have a number of exotic spireas that I have been ignoring, but now I’ve decided it’s time to explore some native replacements.  In the past I’ve worked on properties that have had hundreds of spirea seedlings popping up in mulched beds.  I’ve been fortunate here that I have not seen many seedlings at all.  This may be because of the half dozen plants I have all are the same cultivar, and that cultivar is less fertile.  Or the areas where the spireas are do not see much soil disturbance so seeds are less likely to get a foothold.  In any case I set about looking for a compact native shrub that grows to about 3’ and is relatively low maintenance.  Shrubby St. John’s wort, Hypericum prolificum, and the smaller cultivars of summersweet, Clethra alnifolia cv., are two candidates that I already have.  I instead am going for something new, New Jersey tea, Ceanothus americanus.  These are readily available as small plants by mail order but are not very common in larger sizes at area nurseries.  I have some seedlings on order.  Some of these I will plant out directly and some I will bring along in pots for a season.  According to Missouri Botanical Garden website, these will make good container plants that I can grow on my deck.

Prairie dropseed is notable for its dense mounds of fine foliage. 
In late summer it sends up panicles of pink-tinged flowers. 
I see it as a native alternative to exotic fountain grasses.
Another focus for this year will be to relocate the plants I have into the right place.  High on my list is to move my swamp mallow, Hibiscus moscheutos, to a sunnier location.  I put it on the edge of a swale but over the years it has gone light to heavy shade and is now barely surviving.  Another plant that I’ve allowed to get overshadowed is prairie dropseed, Sporobolus heterolepis.  This beautiful fine bladed grass can grow into 2-3’ mounds, topped by wispy flower plumes in late summer.  While primarily a plant of the Mid-West it is also found on a few sites in the East, possibly prairie remnants.  I allowed mine to get swallowed up and shaded over by some exceptionally healthy coral honeysuckle, Lonicera sempervirens.  I will be getting some new plants and put them into more open locations where they can reach full size.  These are also good candidate for container gardening, so I may set 1 or 2 aside for that purpose.

While I had planted tomatoes here, there was also a crop of black-
and brown-eyed Susans coming in.  These were all first year
rosettes so they did not compete much with the tomatoes for air-space,
but I imagine there was a lot of root competition.
In the vegetable garden I have the opposite problem.  The surrounding wildflowers, particularly the black- and brown-eyed Susans, Rudbeckia hirta and R. triloba, have invaded the beds.  Rather than throw them out I will move them to an area where I am battling Japanese stiltgrass.  The timing should work out where I can use a torch to burn off the first crop of stiltgrass seedlings at the beginning of May and then transplant in the Rudbeckias as the veggie garden is getting prepped.

Speaking of fire, last year I used the garden torch to control weeds in the vegetable garden.  Areas that were cultivated followed by flaming seemed to have fewer weeds than areas that were only cultivated.  However weeds did continue to germinate through the spring so burning is not a one-time thing.  A couple of weeks ago I went out to find a garden bed covered in hairy cress, a winter annual weed.  I got out the torch to see if I could kill these weeds without disturbing the soil.  I checked the bed about 10 days later and most of the cress was dried up.  Aside from keeping the fire under control, my biggest concern is damaging any in-ground irrigation lines.  A quick pass of a torch is enough to melt a soaker hose.   I find the use a the torch most effect at clearing areas where the fencing is buried beneath the soil.  The fire is able to reach between the holes in the chicken wire that would be otherwise inaccessible with a hoe. 

The upper image is immediately after flaming the bed on the right. 
The cress has taken on a darker green color.  10 days later most
of the cress is brown, but a few cress evaded the flame. 
Note that I pulled the soaker hose out of the bed before burning.

Saturday, December 19, 2020

2020 Year in Review

Seems like so many of my blog posts are about removing invasive species.  That is a big part of gardening and landscaping, editing out the things that don’t belong.  That said, the more exciting aspect of gardening is putting in new plants and features and celebrating new milestones.  With that in mind let’s take a look back on new things that I’ve encountered/undertaken in my landscape.

This past year I have been trying to be smarter about where I placed plants.  I’m trying to make the hard choice not to buy something if I don’t have the right conditions, or enough space, for it.  An example is wavy hair grass, Deschampsia flexulosa.  While tolerant of shade I placed on the edge of a shrub border along with some mountain mint.  I was quickly overgrown and did not make it through the season.  This year I planted it in open shade in a dry location where there won’t be much competition.    

I did start some native perennials from seed this past year.  I had good results with downy woodmint, Blephilia ciliata, both in terms of germination and potting up and planting out.  It seems to be doing better in open shade in average to dry soils. This is another candidate as a vinca replacement.  I also had good results germinating and potting up both fireweed, Chamaenerion angustifolium, and pearly everlasting, Anaphalis margaritacea.  Neither of these did well after being potted up or when planted in the garden.  They seemed to have a problem with the soil being too moist, or not draining fast enough. 

A few years back I planted a ring of red osier dogwoods, Cornus sericea, around an existing clump of forsythias with the goal of eventually removing the forsythias as the dogwood got established. The dogwoods on the sunnier, drier side of the forsythias have died off.  I replaced one of these with a gray dogwood, C. racemosa, which is more tolerant of dry soils. Other woody plants added were a shadbush, Amelanchier canadensis, and a choke cherry, Prunus virginiana.  I had planted some these bare root in the past and had limited success.  This time I got larger, potted specimens and I planted them where they would get better light.

I got an American beautyberry, Callicarpa americana, and put it in the same area as some of the Asian species, purple beautyberry, C. dichotoma, which are starting to spread more than I’d like.  As the native shrub matures I’ll pull out the exotic species.  We are located just north of its native range, but with global warming, it will probably do all right here.

American beautyberry, at the top, has larger, more
oval leaves than purple beautyberry (below).

In the spring I removed a sourwood tree that never developed due to being pot bound, even after over 7 years in the ground.  I replaced it with a ‘Wintered’ winterberry holly.  I think the medium-sized shrub will be in better scale for the location, the access path between our house and garage.  I already have a couple of male winterberries in the area, so I should be getting berries to benefit our overwintering birds.

I got a pair of Hydrangea arborescens ‘Haas Halo’, a lacecap form of smooth hydrangea having many more fertile flowers than the very popular mophead cultivar ‘Annabelle’.  I expect these to be better for the pollinators.  They arrived late in the year and I put them in the ground as soon as I could.  I will need to mulch them soon to help them survive their first winter here.

I would like to get all the vinca out of this area and replace
 it with suitable Mid-Atlantic native species.  The new plantings
went in on the right edge.  The foreground is mostly established
Heuchera and Tiarella.

My big ‘new’ project for 2020 was to get busy removing a large bed of Vinca minor from under some evergreens.  I am taking a matrix approach of adding a variety of native plants, compatible with dry shade and seeing what is successful.  Here’s a list everything in the mix: Aquilegia canadense, Eurybia macrophylla (seed grown), Geranium maculatum, Heuchera villosa, Heuchera ‘Palace Purple’, Solidago flexicalis, Tiarella cv., and Viola labradorica.  Two fine bladed evergreen grass-like species are also included: Carex eburnea and Deschampsia flexicaulis.  The violet is looking particularly good in the open right now in December.  We’ll see this spring how suited these are to this dry, partly shady location.

This past spring I planted a number of small trees in the woods, particularly red maples, which I had potted up and held over the winter. I put them in areas where I had killed some mature tree of heaven, Ailanthus altissima, to get a head start on reforestation.   Being somewhat remote these trees did not get a lot of aftercare.  Not surprisingly, most did not survive.  Recently I saw this story about success of natural succession.  They observed that trees that came up from the existing seed bank performed better than ones that were planted.  Maybe adding trees to the already forested areas is more work than it’s worth, especially when there are already naturally occurring seedlings present.  On my last survey of the area I noticed a number of seedlings of hackberries, maples, oaks and tulip trees.

I’m starting to get fruits on some of the native trees that I planted.  I got my first persimmons this year.  I planted this tree about 7 years ago.  I also got some berries formed on the fringetrees, Chionanthus virginicus, but these didn’t stay on the tree long enough to ripen.  I also go some fruit on my 4 year old sassafras.

My first crop of persimmons.  Persimmons are not ready
to be picked until they are soft and starting to wrinkle.  These are ready!

The dark blue sassafras berry has already fallen away leaving
the bright red pedicel.  This effect should be more striking
when the tree has more than two berries.

Freshly planted obedient plant. 
I hope that it will spread here
and help displace the
Japanese stiltgrass.
On the invasive species front I’m making good progress against Japanese stiltgrass using a variety of methods.  The use of pre-emergent herbicides in early spring has been particularly helpful.  I also saw less hairy cress, Arabis hirsuta, in the lawn.  This reduction was probably a combination of pre-emergent treatments and early season mowing to remove flowers before seeds ripen.  By reducing the amount of annual weeds, the lawn is able to knit together more tightly.  This makes it harder for new weeds to get established.  I’ve also planted some obedient plant, Physostegia virginiana, an aggressive native species see how it does against stiltgrass in a shrub border.

For garlic mustard I am including a fall treatment with glyphosate, after most other plants have lost their leaves.  I did this in mid-winter 2020 and it seemed to help reduce the number of mature plants in the spring.

So now that the 2020 growing season is about to close, it’s time to start thinking about what to do in 2021.

Monday, November 30, 2020

Treating Garlic Mustard in the Offseason

Late last winter I began testing the effectiveness of spraying garlic mustard, Alliaria petiolata, rosettes with glyphosphate.  Spraying in late fall through winter has the advantage that most native species are dormant at that time.  While I did not have early satisfaction of find a lot of dead garlic mustard plants it did seem as though there were many fewer blooming stalks by mid-spring.  You can read about that in my blog post ‘Fighting Garlic Mustard with Fire? Or Something Else…

Here's a typical patch of garlic mustard as it looks in November.  It is accompanied here
by Japanese honeysuckle, another invasive that can treated at this time.

This fall I am repeating the spraying.  I had to wait until after some sub-freezing temperatures to make sure that the native vegetation was dormant and hence unaffected by the glyphosate spray.  The advantage of spraying in late fall is that there is less risk to the native vegetation, particularly the spring ephemerals, like Dutchman’s breeches and spring beauties.  Another reason to wait until fall is that a large number of garlic mustard seedlings (80-90%) do not survive the first year, as reported by The Nature Conservancy. So by waiting there will be fewer plants to treat and less herbicide used.  The drawback to fall spraying is that the fresher leaf cover on the ground can hide more of the rosettes.  Since I spray the individual rosettes rather than blanket spray I can move the leaves out of the way as I work and can use a lot less herbicide.  You can find a report on the effectiveness of winter spraying in this paper by Frey, et al

Another invasive that can be treated in fall is Japanese honeysuckle, Lonicera japonica.  Here on my zone 6-7 property Japanese honeysuckle does not go completely dormant and is still susceptible to glyphosate spray.  I sprayed a plot that was fairly dense with the honeysuckle this past week.  We’ll see in the spring if it made a difference.

There are a number of other invasive ground covers that are still green now, but according to the literature I found foliar glyphosate is not particularly effective at this time.  Among these are vinca, Vinca minor, creeping Charlie, Glechoma hederacea, and mock strawberry, Potentilla indica.  So despite my desire to be rid of these I did not waste any of my spray on these unwelcomed plants.

By target spraying I can avoid the native species that still have living foliage.  These include some plants with rounded leaves similar to garlic mustard like white avens, violets, and golden ragwort.  Other natives to avoid spraying include sedges and cool season grasses, ferns and any other early spring plants coming up early.


Winter rosettes of white avens have whitish veins.  You can see how
it compares to the deeply veined leaves of garlic mustard,
marked with white*'s.

In comparison to garlic mustard,
violet leaves are smooth and somewhat glossy.

Golden ragwort leaves are palmately veined
and are regularly toothed on the margins.

A fall trip through the woods also turns up other invasives with distinctive foliage or berries like winged euonymus, barberry, and Oriental bittersweet.  Small specimens of these can be pulled from the moister fall soil. These can also be treated with 20% solutions of glyphosate using the 'cut and paint method.'

I spotted this burning bush/winged euonymus because it still had foliage on it. 
Others with their namesake bright red foliage were even easier to see and pull.

To control garlic mustard one needs to use a combination of tactics appropriate to the situation and season.  Winter spraying with glyphosate will be easier and more effective than fire.  In the spring, pulling or targeted spraying would be most effective.  And for those plants remaining in the late summer, cutting close to the ground or continued pulling will be in order.

Summary of Garlic Mustard Control Measures







Late Fall to Early Spring


Difficult to achieve ideal conditions; Need to keep under control.

A good moderately hot fire is effective, but difficult to achieve.

Herbicide Spray

Dormant season

High kill rate; can be targeted; no soil disturbance.

Spraying toxic materials; may affect non-target species.

Dormant season spraying reduces non-target species effects.


Summer, after flowering

Non-toxic; cutting at ground level nearly 100% effective; minimal soil disturbance.

Labor intensive; disposal of cut stems/flower stalks; use of weed whacker causes collateral damage.

Very effective when done right.


Anytime ground is soft

Non-toxic; very effective as long as most of the root is removed.

Labor intensive; disposal of pulled plants required once flowers are present; soil disturbance.

Very effective.


Tuesday, October 27, 2020

Oh Deer

Even though as winter sets in deer metabolism slows and feeding/browsing damage becomes less obvious, deer still manage to cause some major damage to the landscape

A willow, Salix discolor, that has suffered multiple deer attacks, yet has survived. 
The trunk guards were put on after the fact.

Last February I came to the realization that if I wanted to grow new trees, especially conifers, I would need to protect them from the deer, especially the males during mating season. Here in the Mid-Atlantic November brings on rutting season, the time when white tailed deer mate.  During rutting season male deer rub their antlers against trees and shrubs to remove the velvet from the newly grown horns.  They also will rub trees to mark their territory and to take out their heightened aggressions as mating season kicks in.  What deer prefer for this rubbing behavior are trees and shrubs 1-4” in diameter with smooth bark, like willows and magnolias.  Aromatic cedar and other conifers are also favorites.  Once a tree is marked they will often return to the same one.  At one time I had a nice little Canaan fir, Abies balsamea var phanerolepis,  that I surrounded with chicken wire after it had been rubbed a little.  Two days later all that was left was a bare splinter of a tree.  Now is the time to put up some protection to save some of our precious young plants before they are destroyed.  Following are some of the actions I've taken.

Trunk Protection
Last year I tried horizontal fencing for the first time and did not have great results.  It did not protect a young magnolia from rubbing, but a number of small evergreens did not take any damage.  Based on the photos I have, the deer appeared to skirt the areas with fencing lying on the ground. 

The pink flags indicate where I have put 2"x4"welded wire fencing on the ground around this little Canaan fir tree. 
The idea is that it creates unstable footing that the deer don't like.  The flags help me avoid the fence when mowing. 
I want to add some block underneath to lift the fencing further off the ground.

This year I have plastic mesh poultry fencing wrapped around the trucks of most of the stag-susceptible trees.  For others I have a heavier duty  4” drain pipe around the trunk.  (I’m a little concerned about heat build up under these black tubes.  For that reason I drilled ¾” holes every 6”to aid in ventilation.)  I also used some paper tree wrap on some smaller specimens.  One product that looks very good to me is a white spiral plastic.  It looks like it will protect the bark from rubbing and is open enough to prevent heat build up and not harbor insects.  I haven't bought any of that, yet.  A welded wire barrier surrounding the tree trunk has also proven very effective.  This is most efficient with single trunked trees with few lower branches.  Chicken wire may do a good job of limiting browsing but I've seen it ripped away from small trees that had been rubbed by a buck.

I wrapped the trunks of this fringe tree, Chionanthus virginicus, with plastic poultry fencing. 
It's easy to cut and can be tied together with zip ties or wire.  This material should protect the bark,
but will not support the trunk.

Here I am using a spiral cut 4" drain pipe to protect the trunk of this persimmon tree,
Diospyros virginiana.  I drilled holes in it every 6" to reduce heat build up.  This is
pretty tough material and should hold up to attack.

This Sassafras is being protected with a conventional welded wire cage. 
It's been here 4 years, but now it's of prime size for a deer attack. 
Hopefully the large size cage will be a good deterrent. 
I pulled the cage away during the summer to strengthen the trunk.  
Except for the open mesh materials it is a good idea to remove bark protection in the spring.  Heat and moisture build up can damage the bark and in some cases can harbor insects.  Also too much rigid support can keep a tree from developing a strong trunk.  I found this with my young sassafras.  It was getting floppy and the truck was not able to support the top growth on its own.  I pulled away the support this past spring and now the truck is much firmer.

Here  on this willow I'm comparing a variety of protection devices. 
On the right is a paper tree wrap.  Not sure how that would hold up versus a buck.

In winter deer’s metabolism slows down, but they are still out there browsing.  Evergreens, branch tips and leaf buds are at risk.  Fencing and cages are effective at keeping deer far enough away to prevent browsing.  Burlap warps that are used to prevent winter burn on arborvitae should also work.  Repellents are also helpful.  In colder weather taste-based repellents have an edge because they do not need to be volatile.  It is often recommended to alternate among different repellants through the season so that deer don't get used to any one of them.   So far I haven't done that.  

Reading about all the different recommendations for deer repellants, as well as deer resistant plants, it has become clear that not all deer are the same in regards to their likes and dislikes. Be flexible and try different recipes and products.  I've had good success using Bobbex which contains a variety of taste and odor deterrents. 

Planning Ahead
I’ve seen a number of people on Facebook ask about starting gardens in areas with lots of deer.  My deer seem to test every new plant that goes in the garden.  For new shrubs I usually put a chicken wire cage around them.  As far as planning an new large planting, I like the advice I’ve read in ‘Deerproofing Your Yard & Garden’ by Rhonda Hart.  She recommends fencing in the new garden space before doing any planting.  This is because deer are creatures of habit.  If they have never found anything of interest in an area, then they are not likely to return.  But, once they have found something tasty there, they will make every effort to return.

On the Bright Side?
Deer browsing results in some unsightly damage to many landscape plants.  It is not uncommon to find hedges of arborvitae and junipers chewed back up to about four feet off the ground.  There are some aspects of deer browsing behavior that could be considered beneficial.  The following two photos show where deer have pruned away branches from the lower 4 feet of a yew and a rhododendron.  This sort of pruning opens up the ground plane for lower growing herbs to fill in. In the absence of deer these would be mounds of foliage.  I've also seen this with spicebush, Lindera benzoin, in the woods. This can happen when there is not excessive deer pressure.  Had there been more deer here say 10 years ago these shrubs may not have grown more than a foot tall before being destroyed, unless they were being protected with cages and repellants.

The lower branches of this yew have been munched away over the years.

This rhododendron has been 'limbed up' by deer.

What methods have worked for you during rutting season?  I'd love to hear about them.

Tuesday, October 13, 2020

2020 Stiltgrass Wrapup

As we are coming to the end of stiltgrass season for 2020 I wanted to review what I’ve learned about controlling this invasive species on my Mid-Atlantic property over this year. 

Pulling Japanese stiltgrass, Microstegium vimineum, is an effective means for controlling this annual grass, but it is extremely labor intensive.  While its primary germination period is mid-spring it does continue to germinate into summer, particularly if more openings appear in a previously shaded area.  So you may find that you need to redo areas in late summer that you thought had been taken care of earlier.  This was the case in a shaded woodland where I thought I did a pretty good job clearing the stiltgrass at the end of July.  When I returned to that place in mid-September it was in need of more pulling.  Apparently I left enough scraps around that they were able to regrow.  So if you only want to pull stiltgrass once in a season get every bit out the first time, or wait until just before it goes to seed, maybe early September (depending on local conditions) and then pull out all that you can. 

This was the initial condition, before any clearing in 2020.

This was after clearing in late July, by September this area was
overgrown again with stiltgrass.  This time it only took about 10 minutes
to clear the area.  The underlying Rosey sedge, Carex rosea, still looked good.

While searching for more information about the cleistogamous seeds in stiltgrass (those seeds hidden in the stem), I found a Master’s thesis by Samantha Nestory of the University of Delaware.  There it was noted that Japanese stiltgrass grown in sunnier locations had more cleistogamous seed than in shade, 47% vs 28%.  It also pointed out that, at maturity, there is a cleistogamous flower stalk at nearly every joint along the stem. After reading this I checked out some of the stiltgrass that was ripening.  Sure enough, nearly every joint had a flower stalk hidden or nearly hidden within.  In the woodlands I did not find as many of these hidden flower stalks.  Another observation about JSG is that it is able to put out roots wherever a leaf node, or joint, touches the ground.  By this means a single stiltgrass seedling can cover a large area.  Also residual fragments can quickly reestablish.  I’m not sure what this means for stiltgrass that is pulled then dropped back on the ground.  Will it reroot? 

Next to my finger you can see the flower stalk that was hidden under the leaf sheath. 
In sunny locations by early fall there can be one of these at each joint.

This brings up the topic of how to allocate our most precious resource, time.  While I often dive into some of the most thickly infested areas and rip out the biggest plants, it is actually more effective to begin in less densely infested areas and clear them completely.  After those areas are clear, move on to thicker areas.  The idea is that if an area is totally clear you won’t need to come back to redo it as much.  Whereas while you are battling a thick infestation, the lightly infested area is getting worse and then you end up with twice as much heavily infested space. 

Here's a small scale example of complete removal of Japanese stiltgrass. 
Ideally, I won't have to come back again this year and can spend my time elsewhere. 

This year I was late on reseeding the lawn.  I didn't get out there until early October.  I typically use a bow rake to tear our residual stiltgrass, then overseed with an appropriate cool season turf grass in mid-September.  (We are near the southern limits of where cool season grasses are preferred.)  Overseeding helps to fill in the gaps in the lawn that would otherwise be filled by more stiltgrass.  By seeding in fall these cool season grasses can get established and not be affected when I apply a pre-emergent herbicide in the spring to kill the stiltgrass.  I should have raked out the stiltgrass much earlier, before the seed was ripening.

I’ve had great success controlling stiltgrass in the lawn using pre-emergent herbicides in early spring.  Most products labelled for pre-emergent use to control crabgrass are effective.  I have noticed that the amount of hairy cress, Cardamine hirsuta, has also been reduced (this is due in part to mowing at least once in mid-spring to cut off the flowers before they can set seed.) While the pre-emergent works very well in the lawn, it is not as effective in the rougher meadow areas.

In this mini-meadow I have started to use the pre-emergent herbicide Dimension™
to augment pulling of Japanese stiltgrass.  Naturally occurring species that are flourishing
here include deer tongue and purpletop grasses, wingstem (Verbesina alternafolia)
and wild blackberry.  I have also planted in some panic grass, wild bergamot and brown-eyed Susan.

After two years of treatment in small meadow I have opened up enough space to get some more desirable plants established like wild beebalm, Monarda fistulosa, black-eyed and brown-eyed Susans, Rudbeckia sp.,and grasses like Virginia wild rye, Elymus virginicus, and panic grass, Panicum virgatum.  I noted this year that, in addition to a decrease in stiltgrass, the nonnative invasive bull thistle, Cirsium vulgare, was largely absent this year.  This thistle is a short lived annual or biennial species so is susceptible to control by pre-emergent herbicides.  I have been watching for other changes in the species mix because of the pre-emergent treatments.  Since I have put in some black-eyed Susans, which depend on reseeding to survive, I will not use pre-emergent in that area next spring to see if I can get them to come back on their own.  Ideally I would like to build up a strong network of native species that can exclude the stiltgrass on their own. 

I have not been using post-emergent herbicides on Japanese stiltgrass, but they do have their place in the arsenal. I found research that indicated that the use of grass selective herbicide can be effective, without causing damage to non-grass species.  Fluazifop-p-butyl is a selective post-emergent herbicide that can adequately control M. vimineum with minimal effect on the non-graminoid native plant community (Judge et al. 2005b). Fenoxaprop-p-ethyl, is a selective post-emergent herbicide that provides excellent control of M. vimineum and can maintain or even increase cover and richness of native species post-treatment (Judge et al. 2005a, b, Judge et al. 2008, Pomp et al. 2010, Ward and Mervosh 2012).  Fenoxaprop is not effective on sedges or cool season perennial grasses, like red fescue, so that would be a good thing, since there are many sedge species occupying my woods.  However there are also many shade tolerant grasses like bottlebrush grass, deer tongue grass and mannagrasses that could be affected.  So I would be hesitant to use these useless it was in a very targeted fashion.

These past few years I’ve been using fire, primarily from a garden torch, to control Japanese stiltgrass.  I’ve found that fire is good for clearing a space prior to planting, but not for clearing without a plan for back fill with desirable species.  In some areas I’ve burned the stiltgrass seedlings in early summer only to have the area recovered with more stiltgrass; mostly from rooted stems coming in from nearby plants. Fire alone is more effective in late in season (August) when there is not enough time for new JSG to germinate and reach maturity.  It can work particularly well if there are well rooted perennials in the area.  These perennials are able to resprout after their tops have been singed off.  Cool season perennial grasses are a good example of these.

Here I used my garden torch to burn away the stiltgrass. 
Then I planted some plugs of switch grass, Panicum virgatum

This year I also used fire to dispose of late season stiltgrass that was full of seed.  After realizing just how much seed is contained in a stiltgrass stem, I decided that rather than moving piles of stiltgrass around I would burn what I had in a central location.  Fortunately, I live in an area with plenty of space and that allows burning.  The key to getting stiltgrass to burn well is to allow it to dry out.  I allowed my big piles [photo] of stiltgrass to dry about 2 weeks to get it dry enough to burn rapidly,  In all I estimate I had nearly 2 cubic yards of stiltgrass stems plus thatch from where I reseeded.  This was reduced to less than 2 cubic feet of smoldering ash. [photo].  When burning remember to follow all local regulations.  Don’t burn on windy days, keep the flames under control, and have water on hand to put out any unintended fires and dowse the ashes when done.

These piles of ripe stiltgrass, plus some additional thatch raked out of the lawn,
were reduced to a couple of cubic feet of ash.

Native Competitors
A more exciting aspect of stiltgrass control is finding native plants to fill in or even resist Japanese switchgrass.  Many people, myself included, have noted that golden ragwort, Packera aurea, is very effective at excluding JSG.  

In the woods nearby is a large dense patch of mayapples, Podophylum peltatum, a spring ephemeral.  I have noticed that during garlic mustard season (April to June) there is no garlic mustard growing there.  This year I also realized that there was not any stiltgrass there either, even though the ground is essentially bare save a few sedges and Virginia creeper, once the mayapple has retired for the summer.  I recently saw a post on Facebook where there was a patch of wild ginger, Asarum canadense, that was relatively free of JSG.  These two species spread extensively by rhizomes.  May there’s something to that?  

In early through spring the area circled is covered with mayapples. 
This dense cover seems to have excluded both garlic mustard and Japanese stiltgrass.

There are also grasses that maybe useful.  River oats, Chasmantheum latifolium, grows in dense stands and I have found stiltgrass only on the outer edges.  In the woods the rosy sedge, Carex rosea, has done very well with just a little help from me. In a moist wooded area I noticed that I had an early season grass that excluded the stiltgrass until it went to seed in June.  I’m pretty sure it was a species of mannagrass, Glyceria sp.  (I keyed it out as American mannagrass, G. grandis, but that is a rare species in Maryland, so I will double check when it blooms again next spring.)  In late summer while pulling stiltgrass I came across another patch of grass that had just a very few stiltgrass stems.  Currently unidentified, it seems to block the stiltgrass with a dense layer of thatch from a previous season’s growth.  This is another one to try to identify come spring.

This small, yet unidentified grass seems to have repelled an invasion of stiltgrass.

Next Year:
  • Continue with the pre-emergent treatments on the lawn and in limited areas in the meadows.
  • Focus my efforts in areas to achieve 'complete' removal before moving on to new areas.
  • When burning to clear an area have something ready to fill in.
  • Identify those grasses and see what else is holding its ground.
If you have any additional ideas or know of other competitive native species I'd love it if you could share that here!