Stiltgrass actions for Spring 2019

I have been battling Japanese stiltgrass, Microstegium vimineum, for the past 5 years or so.   Pulling stiltgrass out, particularly in late summer, in the shaded woodlands has been effective in reducing the amount of stiltgrass over several years.  Getting it out of the lawn is another matter.  I've tried raking it out in late summer, and over planting with more desirable grasses (particularly fine and tall fescues).  This has helped, but stiltgrass as a warm season annual, is very adept at filling any gaps in the lawn starting in mid-spring.  While I really like the look of the fine fescues,  particularly the no or low-mow fescue blends, these are slow to establish.  The tall fescues are more aggressive than the fine fescues.  When over-seeded in late summer, these do a better job of getting established and filling in the gaps. 

The area outlined in black has been burned with a garden torch in late summer for the past two years. 
The control patch in the middle was not burned; it has slightly less coverage with perennial grasses.

More recently I've used a garden torch in late summer to eliminate it before it can set seed.  This has been somewhat effective but that is not so practical for a large area.  

Last year I used a pre-emergent herbicide, like those you would use for crabgrass, for the first time.  It was very effective at suppressing the stiltgrass for an entire season.  (I should say that the chemical's effect is probably gone after 2-3 months, but by that time the stiltgrass germination rate has dropped.)  Other perennial grasses were able to start filling in.  I will expand the area of application this year and also test it in some of the meadow areas, as well.

The treated areas have a little more coverage with perennial, mostly cool season, grasses than the untreated areas. 
The brownish spots are mostly zoysia or nimblewill, both warm season species.

While Japanese stiltgrass has a very high rate of germination, I expect that there may be some that waits a season of two to germinate, so these pre-emergent herbicide treatments may need to be repeated for several years.  I will try to leave a small area that I treated last year  untreated this year to see how strongly the stiltgrass comes back. 

In a blog post last year I mentioned several pre-emergents that were effective.  This year I will be using the same as last year, dithiopyr, sold as Dimension.  It has the advantage that I could find it alone, without added fertilizers.  Also, it was less expensive than Preen garden weed preventer (trifluralin).  Timing-wise, the general recommendation is to put the pre-emergent herbicide down when the forsythia are in bloom.  Last year I did this on the early side, just before peak bloom.  This year I will wait just a little later.  My thought is that this will give the existing grasses a little more time to spread before I put down the herbicide, which works by inhibiting new root growth near the soil surface.  I recently found a website that give guidance on when to apply pre-emergent herbicides and other turf related IPM activities called GDDTracker.  A nice feature is that it compares the current and previous year's temperature histories.

I will also try the pre-emergent herbicide in an area that I mow only once a year then leave to grow as a meadow.  In one section I burned off the surface debris.  Half of this I will treat with the pre-emergent, the other half will be untreated (Burn Only).  I will also treat an unburned area with the herbicide to see if burning makes a difference.  The rest of the meadow will serve as the 'control' group.  I am a little concerned about using the pre-emergent herbicide in' wilder' areas.  It could have a negative effect on some of the native annuals there like sweet everlasting, Pseudognaphalium obtussifolium, and yellow fumewort, Corydalis flavula.  But, then again, the stiltgrass has a definite negative effect.

Here is a section of my 'Mown Meadow' where I will do a Stiltgrass/Pre-emergent experiment.  This will give me an idea of how much prep work is needing in this wilder area.

Another action that I will be doing is to plant some bottlebrush grass seedlings, Elymus hystrix, into areas that are infected with Japanese stiltgrass (some herbicide treated, others not).  Bottlebrush grass does particularly well in open shade, conditions that Japanese stiltgrass excels in.  Just removing the stiltgrass alone is not enough, I need to establish some desirable native species to keep the stiltgrass out.

More Maryland Wildflowers - 2nd Week of April

Deciding which native plant to use in a developed suburban landscape was fairly straightforward for me.  I could choose the plants I wanted without regard for to how it would impact the surrounding plant communities.  [Re]-introduction of nearly any native species into a sea of Euonymus and Barberries and the like would be a step in the right direction.

Now that I am working in a rural landscape I am becoming more sensitive to how my new plantings will affect the existing plant and animal communities.  I am cautious about introducing species that don't belong, native or not.  One very helpful resource for me is Native Plants for Wildlife Habitat and Conservation Landscaping Chesapeake Bay Watershed from the US Fish and Wildlife Service.  This publication lists many native species found in the Chesapeake watershed including their native ecoregion (Mountain, Piedmont or Coastal) and state where each is found.  

As a designer I also want to insert some visual effects with form and color.  This may require broadening the plant palette, drawing in materials from other areas and even a few well behaved non-native plants to achieve a particular aesthetic effect.  In general I will utilize a wider variety of plants in the immediate vicinity of a house or other man-made feature.  As I move out to the edges of a property I narrow the plant selection to the regionally native species.  I try to avoid introducing any species that don't naturally belong there.  

So before I get too far in planning and planting new native gardens I need to do some surveys of what is already present.  This (finally) brings me to the topic of what I found growing during the second week of April.  The tree canopy was still pretty open and the woodland floor was really greening up.




The first thing that really hit me was the masses of Virginia Bluebells that were coming into bloom.  These started coming up about a month ago.  Some had purple tinged foliage that has since turned green.



I was very pleased to see large masses of Mayapples coming up, especially I had just bought a half dozen to plant along the driveway.  These look somewhat alien when they first break ground.  They have a large white flower that stays just under the leaf.  

Mayapple leaves open up like umbrellas, 6-8 inches across.  

Once leafed out Spicebush can still be identified by the spicy scent of its bark.

The number of Spring Beauties has finally peaked,
now the blooms remain only in the shadier spots.
Note the garlic mustard off to the right.

Spicebush was another plant that I had just purchased to add to driveway area.  I was very happy to see a large mass of these growing near the creek.  The little flower clusters add an ethereal yellow haze to the scene.  These are not as garish as the Forsythia that are also in full bloom at this time.  






The Spring Beauties, Claytonia virginica, are continuing to come out - now the ground is sprinkled with the pale pink blooms.  The Dutchman's Breeches, Dicentra cucullaria, have also come into fuller bloom.  Some are white and others have a yellowish cast.  

Flowers started out a pale green
before opening up and turning white.

In with the Dutchman's Breeches is a plant with similar finely divided foliage, but this one had tubular yellow flowers.  It turns out that this is Yellow Fumewort, Corydalis flavula.  This native annual is 4-12 inches tall and has glaucous green foliage similar to other Corydalis.  I had never seen this before and was suspicious that it may some of the non-native Yellow Corydalis (C. lutea) that escaped from a garden.  The distinguishing feature from other yellow Corydalis (C. aurea and lutea) is that the upper lip of the flower is toothed.  This species is rare in New England, but not uncommon further south and west.

This winter annual was probably among the
early foliage seen back in January

The upper lip of the flower is toothed.  Also,
 seed pods are visible just below the flower on the left.

Should be getting some yellow flowers from these Trout Lilies in a couple of weeks.
If they are white, then these would be White Trout Lily, E. albidum.

Down in the leaf litter I noticed the spotted leaves of Trout Lily, Erythronium.  No blooms or buds were evident at this time, so I will need to get back down to these is a week or so to catch them in bloom.  As I was climbing back up away from the stream I noticed that the Toothwort were finally in bloom.  The dangling white flowers are not spectacular on their own, but they complement the other ephemerals. The Woodland Phlox, Phlox divaricata, are putting up flower buds, but I did not see any in bloom.  Back up on the lawn I am seeing Common Blue Violet, Viola papilionacea, complemented by the yellow flowers of Rough Cinquefoil, Potentilla norvegica.  Oops, these are actually the non-native Indian Strawberry, Duchesnea indica, see the comments below.

Each flower stalk of these toothworts has a pair
of deeply tri-lobed leaves, hence the epithet  'diphylla'.

Woodland Phlox has formed it flower buds.  Opps, this is actually Cardamine laciniata.

Common Blue Violet has hairless flower stalks,
otherwise this could be Woolly Blue Violet, V. sororia.

Unlike other weedy Cinquifoils, Rough Cinquifoil has
trilobed leaves and relatively large blunt-tipped flowers.  However, this is actually
Indian Strawberry, Duchesnea indica. with larger flowers than the Cinquifoil
and later a red berry.

Along with all of these natives there is a large population of garlic mustard that are beginning to bloom now.  Removing these will be a long and tedious process.  I have put a supply of black trash bags around the property to collect these.  In areas where the soil is moist it is possible to get most of the root out by gently pulling the plant by its crown.  Garlic mustard has a lot of stored energy in its root and may be able to set seed even though it has been pulled out of the ground.  A good practice is to bag them up and let them bake in the sun for a while before sending them to the landfill.  Garlic mustard should not be put into your compost. However, it is edible and you can make a decent pesto from it.