Tuesday, June 9, 2020

Leaves of Three

Poison ivy has three leaflets, the center one has a longer stem.  Leaves have a central vein
with secondary veins branching off from it.  Young leaves are glossy, but older ones are variable
 and leaf margins are all over the place.
After a mild winter in the Mid-Atlantic, it's been a cool, damp spring.  This seems to have brought out a lot of growth in the understory.  Included in this lushness is plenty of poison ivy, Toxicodendron radicans, formerly, Rhus radicans.  As I have been doing some weeding I have been vigilant for ‘leaves of three’, the rhyme for identifying poison ivy.  But that is not the only plant out there that sports three leaflets. 

Following are some common plants that bare some resemblance to the dreaded poison ivy.  Probably the most common look alike in the Mid-Atlantic region is box elder, Acer negundo.  When I first encountered this tree I thought OMG it’s a  poison ivy tree!  This tree reseeds prolifically generating a myriad of seedlings with bright green leaves divided into three leaflets.  While superficially similar to poison ivy, on closer examination you can see that box elder has an opposite arrangement of leaves and branches, while those of poison ivy are alternate.
Box elder has three leaflets that appear very similar to
poison ivy, but branching is always opposite.  Leaf margins are variable
Here they are side-by-side.  Box elder seedling at top has opposite branching,
poison ivy in mid-frame is opposite.  The yellow flowers are green and gold,
  Chrysogonum virginianum.

A close second in my experience is Virginia creeper, Parthenocissus quinquefolia. This rambling and climbing vine has the same habit as poison ivy, but it usually have five leaflets rather than three.  The confusion comes because the younger shoots often sport leaves with three or sometimes four leaflets.  When I spot these I carefully trace the vine back a little ways to see if it also has leaves of five.  Some people have sensitivity to Virginia creeper, but the reaction is not as severe as the rash most people get from poison ivy. 

Virginia creeper is a vine with a similar habit as poison ivy. 
Most, but not all, leaves have 5 leaflets.

Another understory tree that has three leaflets is common hoptree or wafer ash, Ptelea trifoliata. This is not likely to be confused with poison ivy, although seedlings or growth from the base of the tree could cause some concern.  On the hoptree each leaflet does not have a distinct stem (petiolule), rather the leaf tapers sharply to the point of attachment.  While the leaflets of poison ivy are distinct with the central one considerably longer than the two lateral ones.  
Common hoptree grows well in shady locations not unlike poison ivy. 
Note how the leaflets lack distinct stems.

Aromatic sumac, Rhus aromatica, is less commonly encountered.  In the wild it is an upright shrub.  But in the landscape trade there is a shorter, spreading cultivar called ‘Grow Low’ that is becoming very popular.  When I’ve bumped into mine in the woodland edges I froze for a second until I noticed that the leaflets have different lobes and the leaflet stems (petiolules) are all the same length.  On poison ivy the middle leaflet has a longer stem than the other two.

The leaflets of aromatic sumac tend to have rounded lobes concentrated at the tips.

White avens, Geum canadense, has a number of leaf forms.  Some of its basal leaves can have three leaflets but they are not particularly glossy and are generally rough in texture.  Also this species grows in clumps, it is not viney.  

The younger leaves of white avens tend to have three leaflets.  To the lower left you
can see some of the more complex leaf forms.

Barren strawberry, Geum or Waldsteinia fragarioides and the non-native W. ternata, have leaves of three, but the leaf margins are more deeply toothed and the leaflet stems are all very short.
The glossy leaflets of barren strawberry appear to merge together looking
 more like lobes than separate leaflets.

  Mock strawberry, Potentilla  (or Duchesnia) indica, is another prolific ground cover with three leaflets.  It’s leaf margins are regularly toothed and it’s habit is different, spreading by stolons, not vining.  
The leaf surface of mock strawberry is much rougher in appearance than poison ivy.

Golden Alexanders, Zizia aurea, has leaflets that are twice divided, 3 sets of trifoliate leaflets (biternate).  The leaflets are ovate to lanceolate with finely toothed edges.  The long petioles may give the impression of young poison ivy stems.  
Leaflets of golden Alexanders can be seen in the circle at bottom right. 
Also present in this image is Virginia creeper and mock strawberry.

The native clematis, Virgin’s bower, Clematis virginiana, is a weak-stemmed vine with three part leaflets.  While you would want to routinely test the vine strength to distinguish it from poison ivy, an examination of the veins on the leaves would show the difference.  Virgin’s bower has a palmate pattern, with the major veins radiating from a single point; whereas poison ivy’s veins branch out along a central middle vein.  
The ribbed stems of virgin's bower are too weak to support itself
 and it needs something to climb on.

The list of trifoliate plants seems to go on and on.  After I thought I had this pretty well wrapped up I took another look and noticed the leaves of Jack-in-the-pulpit, Arisaema atrorubens, and that reminded me of the trilliums.  These can be recognized by their relatively large leaf size and regular arrangement of leaves.  Arisaema leaves are in a ‘T’ arrangement and those of trilliums are arranged in a regular triangle pattern (120 deg apart).  Can you think of any more poison ivy look-alikes to be on the watch for?

Friday, May 22, 2020

Vinca Replacement

Ever since we moved here 7 years ago I’ve wanted to replace the Vinca (V. minor) from our shady driveway turn-around.  Because I was new to the Mid-Atlantic area I didn’t want to do a wholesale replacement with something I wasn’t sure would work in this mostly shady, dry environment.  So I took a piecemeal approach, trying a little of this and a little of that, leaving most of the vinca in place.  This year I’ve decided to get more aggressive with the replacement, adding some successful species and trying some more new ones.

This was the next area for vinca removal.  It gets morning sun and open shade later in the day. 
It is framed on the right and left with test plantings of Heuchera and foam flower.
My primary reason for getting rid of the vinca is that it is an invasive species.  It is able to creep out of managed landscapes and run rampant in forested areas forming a dense ground cover that excludes native species.  From an aesthetic standpoint, while verdant, it can be rather boring and lack personality. Because of its ability to form thick foliage mats it tends to block out other less competitive species and creating a monoculture, at least on the ground plane.  

Most of the plants I have tried have survived the dry shade, but only a few have competed strongly against the viney invasive.  In all, I have tried nearly 25 native species in this area.  Strong competitors include Jack-in-the-pulpit (Arisaema triphyllum), green and gold (Chrysogonum virginianum), hayscented fern (Dennestadtia puntiloba), bigleaf aster (Eurybia macrophylla), Heucheras (I’ve had success with H. villosa and the cultivars ‘Citonelle’ and ‘Palace Purple’), twinleaf (Jeffersonia diphylla), Virginia creeper (Parthenocissus quinquifolia), zig-zag goldenrod (Solidago flexicaulis), merrybells (Uvularia sessilifolia), golden Alexanders (Zizia aurea), and the low-growing shrub sweetfern (Comptonia peregrina).  Also the non-native variegated Solomon’s seal (Polygonatum odoratum variagatum) is doing well (I imagine the larger native P. commutatum would also do well).  These are able to grow and spread without much help from me.  

Species that survive the conditions but need some help to keep from being overrun include wild bleeding hearts (Dicentra eximia), Alleghany spurge (Pachysandra procumbens), hoary mountain mint (Pycnanthemum incanum), smooth aster (Symphiotricum laevae), foam flower (Tiarella cordifolia), sedges (white-tinged sedge Carex albicans and pensylvanica, and there are some more robust wild ones like loose flowered sedge, C. laxiflora, that do very well).  Barren strawberry (Geum fragarioides, formerly in the genus Waldsteinia) should work well under these conditions, but in my case it seems to struggle.

Species that would be overrun without intervention include Meehan’s mint (Mehania cordata), woodland phlox (Phlox divaricata), and Labrador violet (Viola labradorica).  The only total failure was partridgeberry (Mitchella repens).  This tough little plant does not like to be covered, so between the vinca and the pine needles piling up it didn’t stand much of a chance. 

In this year’s planting I’m adding another sedge, ivory sedge (Carex eburnea), also wild geranium (Geranium maculatum) and, though I’m doubtful about this one, wild columbine (Aquilegia canadense).  I also have some downy wood mint, Bleiphila ciliata, which I started from seed that should do well in dry shade.

On the west end of this planting which gets a little afternoon sun, you can see the
ground hugging green and gold (now in bloom) and the much taller golden Alexanders (to the right).
Other plants include wild black raspberry, which appeared on its own, and several
volunteer trees that need to be pulled out.  
One of the features of vinca that is hard to copy with many native species is that it looks good (that is, pretty much the same) throughout the year with relatively little maintenance.  This is a great attribute from a design standpoint, but that does not make up for its invasive tendencies and relatively low ecological value.  Of the native species mentioned here green and gold and the sedges are evergreen (or nearly so) and the heucheras and foam flowers look good for most of the year.  Where there is sufficient moisture golden ragwort (Packera aurea) would be a very good evergreen choice.  

In the foreground you can see how Pennsylvania sedge pokes through gaps
 in the Virginia creeper (5-leaflets).  The sedge remains green throughout the year,
but looks a little ratty come January.  Another strong presence here is the zig-zag goldenrod,
with its ovate leaves, in the left and center of this image. 

Clearing this area took about 45 minutes.  Much of the time was consumed 
separating the vinca from the good soil after it had been pulled.  The pulled vinca 
was segregated to dry out and die before being put onto the debris pile.

Clearing the new planting space was surprisingly easy.  Since the area was thick layers of decomposed pine needles, the soil was very loose and most of the vinca could be removed with a 4-tine garden cultivator.  What didn’t come out with the cultivator was hand pulled.  I’m sure some bits of vinca remain and these will be addressed as they pop back up through the mulch.  I like using the fork because it hooked on the vines and it minimized damage to the deeper tree roots. 

Most of the new plants are in.  The most obvious are the heuchera and foam flowers. 
In addition to the wild geranium, columbine and ivory sedge are more
zig-zag goldenrod at the back of the planting and Labrador violets to the front edge. 
You can see the garden cultivator I used lying to the left.
Another means of vinca removal is cutting it back low then covering with a layer of cardboard, then mulch or clean soil.  This method would be better where the vinca is more firmly rooted.  I’ve tried spraying it with glyphosate, but the kill rate seemed rater low.

Here's the completed planting from another angle.  The new plants are mostly on the right edge
(see the little white tags?)  In the center of this view are established heuchera and foam flowers.
Using a variety of plant species in this area allowed me to tailor the planting to fit the variations in the site conditions: deeper vs. partial shade, arid vs. average moisture, etc.  Using plants with a tendency to spread both above ground, like foam flower and green and gold, or below the surface, like hay-scented fern helps cover the ground more quickly and allows the plants to migrate through the site to find their best conditions.  The variety also increases the biodiversity, extends the periods of bloom and provides more variation in form and color. 

I think for the next phase of vinca removal I will move to the middle of bed and try some taller species like the great Solomon's seal, white wood aster and more hay-scented fern.

Sunday, March 15, 2020

Japanese Stiltgrass Spring 2020. Time to get started!

Woodland edge inundated with Japanese stiltgrass in 2014.  This was my starting point

Japanese Stiltgrass, Microstegium vimineum, is an invasive annual grass that has taken over many natural woodland areas as well as suburban lawns.  Infestations are particularly bad in the Eastern US from Connecticut, south to Florida and Texas.  I have been posting blogs on my progress battling this grass a couple of times a year for the last 7 years.  Now that spring is rolling around it’s time to get into action.  Here a link to my initial post.

Stiltgrass germinates around the time of annual crabgrass and several pre-emergent herbicides used for crabgrass are effective at controlling stiltgrass.  I have been using a product containing Dimension™ (dithiopyr) on my lawn for 3 years now and it has significantly reduced the amount of stiltgrass present.

This is a comparison of treated and untreated areas in 2019 when the
pre-emergent was applied late.  The stiltgrass seedlings are about
an inch tall at this time.
Last year I tested this product in a mowed meadow area, but the application was at the end of the recommended application time (about 2 weeks late).  I saw a slight reduction in stiltgrass.  I was also concerned that the treatment would affect other plants growing in the meadow, but most of them are perennial species and not as strongly affected as annuals.  On casual inspection last year I didn’t see much difference in the types of plants growing in the treated and untreated areas.  This year I expanded the coverage treating both the lawn and the meadow at the same time at the beginning of the recommended treatment window.  (The meadow was mowed several days before treatment so that the treatment could have direct contact with the soil.)

Here's the mowed meadow after the pre-emergent was applied.  Lots of bare soil now. 
Various grass and sedges are starting to grow.  The wingstem, Verbesina alternfolia,
which dominates this area, has not started growing yet.

I use a website called GDD Tracker 4.0 to tell me when to apply the treatment.  It tracks the days that the average temperature is above 32F.  250 degree-days is the trigger for crabgrass pre-emergent treatment.  Here at my home we hit that on March 10 and I applied the treatment March 12.  (Optimum application time is projected to last through at least 3/21 in my zip code.  Watch out, time is running out!)

Wild Bergamot, Monarda fistulosa, that I planted last year is starting
 to sprout in the meadow with its purple-tinged leaves.  

Friday, March 13, 2020

New Additions for 2020

Every spring (and sometimes in the fall) I make plans on what new or additional regionally native plants I want to add to the garden/landscape.  Here's what I am planning for 2020.

I’m trying big leaf aster, Eurybia macrophylla, from home grown seed again this year.  Last year I harvested seed from an isolated plant.  This year I got it from an area that had several distinct individuals.  Many asters are self-incompatable, so the seeds that I am using this year are more likely to be fertile.  (Though tiny, they did seem to be thicker this year).  I’m still waiting for them to germinate; it’s been 14 days, so far.  Over the years I've had a hard time getting good levels of germination from asters and goldenrods.  Fortunately, in nature, they do just fine on their own.  (I’m also comparing unstratified to 30 days cold moist stratification.  We’ll see.)

There bigleaf aster are doing quite well in the dry shade under
the eaves along the foundation of a house.

I’m also stating some more switch grass, Panicum virgatum, from seed that I bought 3 years ago and kept in a refrigerator.  I was pleased to see that they are still viable, germinating beginning in less than a week.  They were planted in seed starting mix, under lights and bottom heat to warm them to 65-72 F (no stratification). I've been planting these out in a meadow area as plugs where I am trying to displace the very invasive Japanese stiltgrass, Microstegium vimineum

Here's an American lady butterfly on its host plant, pearly everlasting.

The tiny seeds of pearly everlasting give way to tiny sprouts (little green spots in this photo). 
After 30 days of cold, moist stratification, these germinated on the soil surface after only 3 days.

The bright pink flowers of fireweed should
stand out through mid-summer in the meadow.

Some new seeds that I am starting now are downy wood mint, Blephilia ciliata, pearly everlasting, Anaphalis margaritacea, and fireweed, Chamaenerion  angustifolium (formerly an Epilobium).  In the past I’ve tried the latter two before from seed with little luck.  This time I’m stratifying at lower temperatures, 37 vs 45 F.  Again, we’ll see.  Of these plants, fireweed can be pretty aggressive, once established.  My plan is to put it into a mown meadow that is home to other tough plants like wingstem, Verbesina alternifolia, Panicled tick trefoil, Desmodium paniculatum, and a variety of thistles.

When we first moved here one of my goals was to rip out all the vinca that was growing along our shady driveway and replace it with native species.  Before going whole hog I wanted to test some species to see which ones were strong competitors in this dry, shady location.  Seven years later and I haven’t made a lot of progress.  Plants that are doing well and slowly expanding are Green and Gold, Chrysogonum virginianum, and Pennsylvania sedge, Carex pensylvanica.  Alum root, Heuchera villosa and cultivars, and foamflower, Tiarella cordifolia, are surviving but not expanding rapidly, I have high hopes for the hay scented fern, Dennstaedtia punctiloba, but it has not expanded much in its first 3 years.   This year I decided to get moving again on this project.  I’ve ordered a number of dry shade tolerant plants:  Red columbine, Aquilegia canadense, ivory sedge, Carex erburnea, wild geranium, Geranium maculatum, Zigzag goldenrod, Solidago flexicaulis, and Labrador violet, Viola labradorica.  Also some of my big-leaf aster will go in, if/when they are successful from seed. 

These Green and Gold, are doing well in an area that was covered in vinca. 
They are continuing to spread but they have not out-competed the vinca.

Last year I potted up some of the red maples that were coming from seed.  I have killed a number of invasive Ailanthus that were dominating the canopy in one area of my woods.  I wanted to give the newly opened up woods a jump start with some native trees.  Red maples, being more shade tolerant, seem to be a good choice (and they’re free).  Since we have sugar, red, and silver maples here it is possible that these seedlings could be any of these or even a cross between red and silver, Acer x freemanii.  When they were young they looked like red or sugar maples.  But as they developed it became harder to tell from the leaf shape, they weren’t as deeply divided as a sliver maple, but not all simply 3-lobed like the ideal red maple.  They all seemed to have overwintered successfully under some shrubs along the garage foundation.  Later this spring I will start putting them in.

Here's my collection of maple seedling after I potted them up last spring. 
Most of them had the 3-lobed leaves indicative of red maple.  As they grew on
it became less clear that these were all red maples.

Saturday, February 15, 2020

Deer Wars

Well maybe not full scale wars, but I need to find an acceptable balance where some new plants are allowed to survive to maturity.  The first battle was in creating a vegetable garden.  There using a double fence, two 4-5' tall fences about 4' apart, has been pretty effective at keeping the deer out.  Next was controlling deer browse on shrubs and new trees.  In those cases I have been having some success with repellent sprays, like Bobbex, and using wire cages around susceptible plants.  Plant selection is also important, by avoiding deer favorites like arborvitae and roses, I save a lot of heartbreak.

This pussy willow (Salix discolor) has survived repeated
deer 'rubs'.  The cambium layer has healed but left
the original heartwood exposed.  The short trunk guards
are not tall enough to protect all of the trunk
 susceptible to deer rubbing.
The next phase of the battle to wage is rutting season when the bucks look for the perfect tree or shrub to rub their antlers against to clear them of velvet, the outer layer that supports the growth of their antlers.  Here in the Mid-Atlantic rutting season begins around the end of October and runs for 1-2 months  The ideal targets for velvet removal are flexible saplings, 1-2" in diameter and over 2' tall.  Small evergreens seem to be a particular favorite.  This is bad news for the few Christmas trees that I am trying to grow.  I’ve lost a number of nicely shaped trees once they reach about 3 feet in height.  Trees with lots of stiff branches low down on the trunk are not as desirable.

I have a stiff 4' tall welded wire cage around this young sassafrass. 
This guards against deer browse but an aggressive buck
may be able to tear it loose.
I have been protecting the newly planted evergreens with chicken wire, which is good for a couple of years.  Once the trees get taller I had the bucks tear away the chicken wire.  Another problem with chicken wire cages is that they interfere with the shape of the tree. 

This year I tried a new technique that I heard about a number of years ago.  Lay chain-link fencing horizontally on the ground around the trees you want to protect.  The idea is that this creates an uneven surface on the ground that the deer find uncomfortable to walk on.  To be effective the fencing needs to be held a little bit above the ground level to create an unstable surface, particularly for hooved animals. It's kind of like a cattle guard. I was not able to get hold of any scraps of chain link, but it did salvage some 5 foot tall welded wire fencing to test this concept out.  The nice thing about the welded wire is that it is stiff enough that it can be held above the ground surface with fewer supports than chain link. 

The pink flags mark the corners of the horizontal fence.
I cut 6 foot long sections of the fence and cut a slit half way though in the middle to accommodate the tree trunk.  I turned the edges down so that once put on the ground the fencing would not lie flat, but would arch up a little.  The last week of October I laid out these horizontal fences around several small Christmas trees, a pussy willow (that had been damaged in the past) and a sweet bay magnolia (about 1.5” in diameter)

Here is a deer just skirting along the edge of the horizontal fence,
keeping a couple of feet away from the tree trunk.
It could probably lean in to munch on the branches if it needed to.

Results were mixed at best.  I didn't lose any Christmas trees (either with or without protection), but it did get some damage to other young trees despite having both the horizontal fence and a chicken wire cage.  Where it wasn't effective it may not have been raised enough off the ground or it may need a wider protection zone.  Another reason may be that it is just not very effective.  Advantages (if done right) are that it has a low low impact on appearance of the landscape (can't be seen from a distance) and it does not interfere with form of the tree or shrub.

This Douglas fir is getting some attention from a buck.  The tree is surrounded
by chicken wire but does not have the horizontal fencing.  This particular tree
has multiple trunks so it may not be a choice candidate for antler rubbing.

This 4" drain pipe was cut in a spiral using a hacksaw.
Note the ventilation holes.

I was very sad that the deer attacked my magnolia.  It had finally gotten tall enough that the leaves were out of reach of the browsing deer.  For single-trunked trees some sort of bark protection may be the best route.  You can buy these like the spiral wound tape, plastic mesh, tubes.  Also chicken wire, hardware cloth or welded wire fencing can be wrapped around the trunk.  Alternatively you can make them from flexible drainage pipe.  One concern with this black pipe is heat build-up in the pipe during the winter.  To reduce this I drilled ¾” holes every 6 inches to let in air.  It would be better to use white-colored piping (does that even exist?).   You need to be careful not to damage the bark when putting rigid tubing around a tree.  Another feature of the  plastic pipe is that it makes the trunk appear larger than the 1-2" diameter that the bucks prefer.

 Bugs can also hide out under the protective pipe or wraps.  So you need to watch out for that.  This year I put truck protectors on too late, after the damage was done.  But I went ahead and put them on anyway, just in case a buck came back to finish the job.  For the spring and summer I will remove the tubes so that the trunk can heal and develop naturally.  I will just need to remember to put them back on in early fall.  

Here's my sweetbay magnolia with the  protective tube in place. 
The arrow indicates how high up the deer damage went
 before the tube was put on.  The antler rubbing happened despite having
 both the horizontal fence and a 3' tall chicken wire cage.

I also tried wrapping some plastic mesh fencing around some trees.  This was easier to do but I’m not sure if it will offer as much protection as a solid tube (better than nothing?)

This plastic fencing was very easy to put around the tree. 
Heat build up is not an issue, but I'm not sure how much
 protection it will really offer.

So, in review, for single-trunked trees a trunk wrap or protector of some sort should do the job.  For trees and shrubs with low branches, a perimeter cage, well anchored to the ground, should do the job.  The horizontal fencing as described here still needs some fine tuning but holds some promise since it does not interfere with the growth of the plant and it has a low visual impact.

Monday, January 20, 2020

Fighting Garlic Mustard with Fire? Or Something Else...

A couple of years ago I added a garden torch to my arsenal of tools to maintain the landscape.  Fire can be a natural and effective tool in controlling invasive species and is one of the better ways to maintain a prairie ecosystem.  But, fire can also get out of control and its effectiveness is diminished if it is not timed properly or its intensity is not sufficient to destroy the target species.  On the garden scale a garden torch is a good way to kill weeds growing in cracks in a drive or walkway.  It is also effective at killing young seedlings, particularly annuals.  I found it particularly useful for  for clearling plants away from the partially buried wire fence around the vegetable garden.  Perennials and established plants require much more heat to kill them.  For established weeds repeated burning 2-3 weeks apart may be necessary.  Though it seems counter-intuitive, flaming moistened soil is more effective at killing young plants and seeds than dry soil because the moisture helps conduct  the heat through the soil.

Here's my Benzomatic garden torch.  It is light weight and a good size to fit into tight spaces. 
The one pound tank lasts an hour or so, depending on how big a flame you use.  

I originally got my torch to use on Japanese stiltgrass.  While spring burning does kill the sprouts effectively, other plants are actively growing at this time and the fire will set those back as well.  Also stiltgrass germination occurs over an extended time period, so multiple burns would be necessary.  For stiltgrass in a cool season lawn, burning in late summer, while the perennial grasses are in summer dormancy, is very effective at preventing the stiltgrass from setting seed.

This success with stiltgrass got me to thinking about using the torch on garlic mustard, Alliaria petiolata.  Garlic mustard is a monocarpic biennial. It spends its first year as a rosette of deeply reticulated, reniform (kidney-shaped) leaves that builds up energy reserves in its fleshy white roots.  The following year it sends up a 2-4 foot flowering stalk in mid- to late-spring. It seems that winter time might be a good time to take out the garlic mustard.

Winter rosette of garlic mustard.

In the past when I have tried to burn garlic mustard I found I had to hold the flame on the plant for a long time before I could see much damage.  Before burning through a lot of propane, I decided to do a little research on using fire against garlic mustard.  The U.S. Forest Service has reports that document the effects of fire on a number of important plant species, including invasives.  Follow this link to the Forest Service report on garlic mustard.  A study authored by Victora Nuzzo for the Illinois Department of Conservation in 1990 compared the effectiveness of fire, herbicide and cutting for the control of garlic mustard.  They found that for fire to be effective it needed to be moderately intense and carried out in early spring.  Ideal burning conditions were often not available.  Herbicidal spray treatments were most effective in early fall and spring, timed for when native vegetation was dormant and thus less susceptible to the herbicidal effects.  One study out of Ohio showed that winter-time application of glyphosate when temperatures were between 25-45 F was very effective at killing garlic mustard rosettes.

Cutting plants after seed formation had begun in mid- to late-summer was very effective at reducing the number of plants in subsequent years.  Cutting at ground level resulted in nearly complete mortality, while cutting a couple of inches above the soil surface was only about 70% effective at killing the plant.  Since flowers and seeds continue to develop on cut stems, it is important to bag and dispose of all the garlic mustard cuttings.

Pulling mature garlic mustard is also very effective, and can be done anytime.  As with cuttings, if there are any flowers present the pulled plants should be bagged and disposed of.  While completely non-toxic, pulling garlic mustard is labor intensive (pulling and clean-up) and disturbs the soil.  This allows for the germination of additional seeds buried in the soil.

Here are some of the interesting garlic mustard facts that I came across while researching this post:
  •        Seeds lie dormant for a year before germinating.  This means you may not see the effect of control measures on new seedlings until the second growing season.
  •         Flowers are self pollinating; many are already pollinated before the flower opens.
  •         Flowers can photosynthesize.  They can continue to mature to form seed even after they have been cut or pulled.
  •        Plants are monocarpic.  They will continue to live until they set seed, even multiple years.
  •        Seedling mortality is high, 80-90%, during their first year.  More effort should be expended on removing maturing plants particularly in late fall to early spring.
  •       Of the common herbicides, glyphosate and triclopyr are very effective at controlling garlic mustard, 2,4-D is not.

So, Burn or Not?

So to answer the original question, should I use fire to control my garlic mustard?  The answer, for me, is no.  I will need to use a combination of tactics appropriate to the situation and season.  Winter spraying with glyphosate will be easier and more effective than fire at my location.  In the spring, pulling or carefully 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.

To test this I will target spray with 3% glyphosate in a section of the woods in February if (when) we get a stretch of days in the 40’s with no rain and see how that compares to untreated areas.  (February seems a little early, but we are in the 60’s in early January, so plants may be getting woken up a few months before normal.)  Rather than blanket spraying I will try to target the spray onto existing rosettes.  One of the reasons to use target application is to avoid those few natives that are still in leaf through the winter. 

Some native plants that may look similar to garlic mustard rosettes include violets, Heuchera, Tiarella, and white avens (Geum canadense).  Ground ivy (Glechoma hederacea) and common mallow (Malva neglecta) are some weeds that look similar, but are not currently on my hit list.  (I found no studies that indicated that ground ivy is susceptible to herbicides in winter.  Based on that I wouldn't waste time and materials treating it in the winter.)

Compare the palmate lobed leaves with the deeply veined (reticulated), bright green leaves
of the garlic mustard.  Here, pulling is the only option for removing the garlic mustard.

The leaves of foamflower are distinctly lobed.  The vein pattern
is different from that of garlic mustard.

Golden ragwort has regularly toothed leaf margins and a more linear vein pattern.

White avens over winters as a loose rosette of leaves.  Though most winter leaves
 have 3 lobes, some appear roundish and vaguely similar to garlic mustard.

The leaf shape of common mallow is similar to that of garlic mustard,
but the vein pattern is different.

In areas where I am more actively managing the garlic mustard I will continue pulling plants through late spring (before flowering).  In late summer I will see if there is a practical way to cut the plants close to the ground without leveling the surrounding vegetation.  Otherwise, keep pulling!

This table summarizes the garlic mustard control methods mentioned in this post.

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 damage to non-target species.
Summer, after flowering
Non-toxic; cutting at ground level nearly 100% effective; minimal soil disturbance
Labor intensive; must dispose of stems/flower stalks; use of weed whacker causes collateral damage.
Very effective when done right.
Anytime ground is soft and easily worked
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

Saturday, November 2, 2019

Surprise Plants

Living in a more rural area means that there is the possibility that there are still many native species lurking just out of sight.  Here are some of the plants that I have found growing spontaneously around our property.  Most of these have benefited from the removal of invasive species.  Reducing competition for light allows for germination from the seed bank and stronger growth overall.  Removing the cover, especially Japanese stiltgrass, also makes it easier to see what all is growing.  

The scalloped leaves along the stem made me think
that this was ground ivy, but the flower on top
quickly showed me to be wrong.
Among one of the first species of native annuals I tried to grow was clasping Venus looking glass, Triadonis perfoliata.  I had no luck in getting the seeds to germinate under controlled conditions (moist stratification, sterile soil, under lights, etc.)  This past spring, I came across some blooming plants as I was looking for some other seedlings in an area where I have been pulling out Japanese stiltgrass.  I can't say for sure that its emergence was due to reduction in stiltgrass, but it was much easier to find with less competition for space.  Since this species is an annual, continued success depends on it producing seed and getting that seed in contact with the soil.  Having the area less clogged with stiltgrass should help it along. 
When I first noticed it, I saw the clasping leaves on a long stem and thought it was ground ivy.  Before I could pull it I noticed the bright lavender flower at the end of the stem.  Closer examination shows that there were calyces in most of the upper leaf axils.  These had probably already bloomed out.  I will keep an eye on this area next spring to find this plant again. 

The round, glaucous stems on this bush indicated that this was some sort of raspberry. 
The berries were initially red, but all turned black over the course of a few days, so it some sort of black raspberry

When we moved here in 2012 many of the unmown areas that got any sun at all had the invasive wineberry, Rubus phoenicolasius, growing in them.  Fortunately this is not a strongly growing plant and it can be suppressed by cutting it back on a regular basis (at least once a year). It is also fairly easy to pull.  While the stems are covered with sharp bristles, these are not very stiff and will not penetrate my gardening gloves.  I was disappointed that I could not find any native raspberries (we have a ton of wild blackberries) growing in or around the woods.  In 2017 I started noticing a different berry plant showing up in various places, many of those that had been covered with wineberry.  The trifoliate leaflets and bluish blush on the rounded stems pointed toward some sort of raspberry.  (See this link to Illinois Wildflowers for way to tell raspberries and blackberry plants apart.)  It didn't matter which, as long as it wasn't wineberry (or more blackberry).  This spring these new plants flowered and produced fruit.  The berries were initially red, then turned black as they ripened.  While I have not nailed down the ID, it's a pretty good guess that these are native black raspberry, Rubus occidentalis.

I don't know if these are from an existing seed bank, or were brought in by wildlife.  Next year I will pay closer attention to the flowers to try and confirm the ID; although there are only three species of raspberries that are black, most are red.  If these came in via wildlife, they may be from some cultivated varieties rather than strictly wild.  On tasting the black berry I finally appreciate what the flavor 'black raspberry' really is like.  Jolly Ranchers have the taste right.   

Two years after I started removing the invasive species from this area,
these American germander have formed a hedge of their own.

American germander, Teucrium canadense, was one of the first native plants to emerge from what was before a dense hedge of wineberry, garlic mustard and Japanese stiltgrass.  Since this plant spreads by rhizomes and is a prolific reseeder it may be able to hold its own against the stiltgrass.  Peak bloom is in mid-summer at which time it is easily identified by the stamen arching out above the slipper-shaped, white to pale pink flower.

You can see the small white flower clusters coming
out of the stem at the bottom of this photo.
Sweet cicely, Osmorhiza claytonii, is a pretty common woodland edge native.  I usually find it along paths in partly to mostly shady wooded locations.  I usually notice it because of the deeply lobed bright green leaves and the hairs that cover the leaves and stems that catch the light.  As more invasives are removed from the understory small plants like this one are easier to spot.  Also as space opens up native like sweet cicely can fill in.

This large, about 5" long, trumpet-shaped flower is unlike most native species in our area. 
Is is actually a southwestern native but has naturalized as far north as New England.

Afterthe removal of a large pine tree I've been finding new plants cropping up all around it.  These were probably buried in the seed bank and were stirred up by the work crew or were just sitting there waiting for more light and moisture to encourage germination.  One plant that really surprised me was Sacred Datura or Angel's Trumpet, Datura wrightii.  Native to the western states, this plant is probably a garden escapee, possibly grown by the previous owner or flown in by birds. In colder climates this plant behaves as an annual though is is listed as cold hardy to USDA zone 4.

Though a little tattered Robin's Plantain seems to be
getting established in a shady portion of the lawn.
We have a number of fleabanes, Erigeron, growing here.  Most of the plants are either annual fleabane or Philadelphia fleabane, E. annuus or E. philadelphicus, respectively.  In a shady portion of the lawn (where grass doesn't grow well) I noticed a new white daisy-like flower.  It was growing up from something that looked like plantain.  While I'm not absolutely certain I'm pretty sure that this new find was Robin's Plantain, Erigeron pulchellus.  When it's in bloom I try to avoid mowing it so that it will have a chance to spread.  Since Robin's Plantain likes limy soils and has persistent green basal leaves it is a welcome addition to my natural lawn.