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.

Making a Plan to manage Japanese Stiltgrass

My wife and I have been on a campaign against invasive plants on our property.  Our two main targets are garlic mustard and Japanese stiltgrass, Microstegium vimineum.  The spring time is when our focus is on garlic mustard, when the ground is soft and before it begins to flower.  In late summer our focus switches to stiltgrass.  I am trying to come up with a program that works for me: how can we eliminate as much stiltgrass with the least amount of work and without causing too much collateral damage. 

This is a shady area that used to be mowed.  The stilt grass has moved into
the gaps and is crowding out the native vegetation.

We've been pulling plants from planting beds as they appear (compulsive behavior), pulling larger plants and weed whacking in late summer.  Recently a friend pointed out how much stiltgrass was growing in the lawn.  I realized that this lawn weed may be creating a large mass of seed that could easily recontaminate the surrounding woodlands.  So I'm now including the lawn in the project. 

The Plan

As the weather has gotten cooler I could see how stiltgrass has taken over large swaths of the lawn.  This effectively creates bare spots that are prime territory for stiltgrass to resprout in the spring.  Remembering that one of the best to control lawn weeds is to have a thick turf, I decided that I should be more aggressive about filling in those bare spots with desirable plants. My general plan is as follows:

• Pull in early August.  This allows a second crop to germinate, but not enough time to mature before frost.
• In natural areas minimize disturbance to soil and encourage existing native species.  Cut stiltgrass low when flowering starts, about mid to late August to early September.
• In disturbed areas (lawn) try to add more competitive ground covers, like cool season grasses to get established before stiltgrass germinates in mid-April (WVa).  

This will be a 5+ year program to get rid of the current crop of seeds already in the ground.  There will be continued outside pressure from surrounding areas infested with stiltgrass. 

Japanese stiltgrass is turning brown in the lawn early October.
This thatch can be slow to break down,
leaving a gap for more to germinate in spring.

In late fall and winter stiltgrass appears as a persistent golden-brown thatch.  The usual invasion route is into areas of disturbance in an otherwise natural space.  Deer are also vectors for the spread of stilt grass.  They often bed on top of stiltgrass infested areas, then carry the seed with them, dropping it along their paths.  While they will sleep on stiltgrass, deer do not feed on it.  Instead they feed on native vegetation, further helping stiltgrass to outcompete native species.

In late August/early September a flush of growth is a signal that stiltgrass is maturing and seed production is about to commence.  Waiting to cut the grass at this time does the maximum damage to its reproductive cycle.  Early season mowing or whacking of stiltgrass stimulates early flowering and a lower, harder to remove growth habit.  Pulling stiltgrass early in the season creates openings that allows additional germination.  By waiting until late in the season these late germinated seedlings will not have time to mature before they are killed by the colder temperatures. I really like the idea of tricking it into germinating late in the season.  Also plants pulled out before the seed has matured can be left to decompose.  After the seed has ripened in mid- to late-September plants should be bagged and landfilled to prevent spreading of the seed.

I found this recommendation by West Virginia forester, RussAnderson:

"If the area where stiltgrass control is desired includes a lawn that is infested, all regular mowing of that portion of the lawn should cease around July 15 and allowed to grow for a month before mowing again. Normally, during this 30 day period the stiltgrass will significantly  outgrow all other lawn cover making it both easier to identify and easier to kill. To ensure the highest proportion kill possible in the stiltgrass the best option is to mow the lawn, especially where the stiltgrass is present at the lowest blade setting. Completing the mowing during the hottest and driest conditions possible will further enhance the kill in the stiltgrass. If the mowing of the lawn is successful, regular lawn grass will begin to fill in the dead spots almost immediately. If the stiltgrass is mowed before it is allowed to go to seed the number of stiltgrass seedlings on the lawn will greatly decline in succeeding years."

It's hard to leave an area of lawn unmown.  But if this works, consider all the labor and chemicals saved compared to removing stiltgrass by other means.  Also this can be a positive step by NOT doing something (mowing for a month), rather than continually mowing. 

Here's that same shady area after weed whacking and raking up the cut stiltgrass (upper left).
Pink flags indicate the location of desired native species left in place.

Weed whacking stiltgrass from hard to mow areas should be done in this late August period.  Cutting as low as possible removes both the upper flowers as well as the lower cleistogamous flowers hidden in the stems.  If there are native species going to seed in the area, waiting until they mature can help reestablish native populations.  In some smaller areas I surveyed for native species and flagged them so that they could be avoided while whacking the stiltgrass.  

Cool season turfgrasses

Since each fescue plant is so small the seeding rate
 is fairly high, 5 lb/1000sf, to get good coverage.

Tall fescue is a good choice for high traffic sunny areas, but this is not a North American species.  Since my focus is on using native vegetation and natural appearance, I am using a mostly native fine fescue blend. (Eco-grass from Prairie Moon) of red and creeping fescues for the shadier areas.  In the wilder areas I am trying a blend of native grass species.  This is an experiment to see if I can get good cover with these prairie species used in a lawn-like environment.  However, a prairie is managed much differently than a lawn and there is a good chance that this approach will not be successful.  Many of these native grasses need a year or two to put down roots before top growth takes off.  Ideally these species should be allowed to mature for a season or two before they get chopped back, by mowing or grazing.

For sowing, I first used an iron rake to clear out the stiltgrass thatch.  (Looking back, if had done this in early September I could have limited the stiltgrass seed production even more.)  This also loosened the soil surface.  Then I broadcasted the seed.  Finally I used the flat edge of the rake to push the seed in closer contact with the soil.  To get good germination and establishment of the seedlings the ground should be kept moist.  I usually try to time fall seeding with the weather forecast to take advantage of rainfall to get the grass started.

About 10 days after seeding with Eco Grass a fine green haze is covering this previously barren area.

Most commercial turf grass blends contain annual and perennial ryes which are fast growing and fill in quickly.  The fine fescues used here do not grow as quickly and it will take longer to have that full look.

Native Grasses

With that in mind I decided to try this as an experiment.  I selected species that tolerate grazing, where they would be eaten back to 3-5 inches, since mowing it is a similar action.  Since I am fall sowing I selected mostly cool season grasses, with the hope that they will get established before the stiltgrass germinates in the spring.  Also, there are warm season species in the mixture to try and fill in the gaps when the weather warms.  The grasses I selected where mostly native to Maryland or the mid-Atlantic region.

Name	Botanical Name		Season	Exposure	Seeds/pound	Sun mix ratio	Shade mix ratio
Canada rye	Elymus canadensis		cool	Part	100K	8	4
Virginia rye	Elymus virginicus		cool	Part	100K	4	2
Side Oats Grama	Bouteloua curtipendula		warm	Full	150K	6	1
June Grass	Koeleria macrantha		cool	Full	2000K	1	0
Fall or Beaked Panicgrass	Panicum anceps		warm	Part	--	0	1
White clover	Dalea candida		--	Full	260K	4	0

I made up two seed blends one for full sun and the other for part shade.  The majority of the seeds are cool season grasses.  The weight ratios for each are listed in the table above.  When making up a seed blend you need to account for the number of seed per pound and the seed viability, usually listed as pure live seed (PLS) which is seed purity times the germination rate.  This is my first time trying this so I can't be sure that it will work.  I did put some seed into a new meadow area that will not be mowed regularly.  This will serve as my 'control' group.

A better way to sow these native grass seed would be to use a seed drill and put them in 1/4 to 1/2 inch deep.  Instead, I sowed them the same as I did for the fine fescue, but at a much lower rate (pounds/sf).  The recommended rate for Eco Grass is 5 lbs/1,000 sf while for Canada rye it is on the order of 3 oz/1,000 sf.  Since the ryes and other native grasses are much larger plants when mature, compared to a single fescue plant, it takes only a few seeds to get the same coverage.

June grass has a seed similar fescue is size;
however, the resulting plant is much larger

Side oats grama has a lot of husks included, but
these are accounted for in the PLS calculation  

Virginia and Canada ryes look similar.  

If I don't see sufficient germination by next spring I will go back to a standard turf grass blend.  It's better to fill in with something than leave space for stiltgrass.

15 days after seeding I'm seeing some new grass growth in some of the sunnier areas.
The shade areas are not showing definitive signs of new grasses.

We were surprised to find this obedient plant
blooming late in the season.  I don't know if this is indigenous
 or if it escaped from an earlier planting by a previous landowner.

Other strategies

Broad spectrum (glyphosphate) and grass specific herbicides are effective on stiltgrass, but they may impact surrounding vegetation.  I found a mention of using a dilute solution of Fusion® (grass specific herbicide) to kill stiltgrass with relatively little collateral damage to native perennials and grasses.  Another tool is the use a preemergent herbicide in spring.  However, since stiltgrass continues to germinate throughout the spring and summer, a single treatment alone would not be effective.  A preemergent would also suppress germination of other desired species.

One of the side benefits while pulling stiltgrass is that it gets you looking closely at plants and nature.  We've spotted a number of interesting plants this year while thinning out the overgrown edges of the woodlands.  Most recently I spotted a dark pink Obedient Plant among the grasses.

References

The following are some additional websites with useful information on dealing with Japanese stiltgrass: 

http://nyis.info/index.php?action=invasive_detail&id=32

https://www.bae.ncsu.edu/programs/extension/wqg/northcreek_images/microstegium.pdf
http://www.bioone.org/doi/abs/10.1614/IPSM-11-00018.1

http://www.gardensalive.com/product/take-a-stand-against-stiltgrass?ai=1358