Stiltgrass management, part 2

After trying to remove as much Japanese stiltgrass as possible in late summer, the next step is to fill in the gaps with more desirable plants. My approach last year of seeding in native grasses like Canada and Virginia ryes did not work out too well.  There were some good reasons for my disappointing results.  I needed to plant  these relatively large seeds more deeply to get better germination.  Also these new grass seedlings need 2-3 years to establish before mowing back, or using as pasture.  It would be better to use these big perennial grasses in a meadow planting where mowing is done only once a season.

This year I am trying a more conventional route with the filler grasses.  I will be using commercial turf grasses that are selected for rapid growth and formation of a dense turf layer.  This is what I need to exclude the stiltgrass.  By planting these cool season grasses in the fall they have a chance to germinate and fill in before the stiltgrass starts growing in mid-spring.

I divided up the stiltgrass infected areas into full sun, part sun and mostly shade and selected a seed mixture appropriate for each condition.  For full sun I selected a blend of tall fescues with just a little Kentucky bluegrass.  For the part-sun areas I have a blend or both tall and fine fescues with a little perennial rye and Kentucky blue grass.  For the shade areas I am using a blend of fine fescues selected for low maintenance.  This year I am using Eco-Grass from Prairie Moon, but there are other blends such as No-Mow from Prairie Nursery and Eco-lawn from Wildflower Farm that should work as well.

Most commercially available cool-season turf grasses are not native to North America with the exception of some of the fine fescues, in particular red fescue (Festuca rubra).  You can find detailed information about which turf grasses are appropriate for your region from your state's cooperative extension.  For example the Maryland Extension Service has a listing of recommended grass cultivars that were tested locally.

Before buying seed this year I shopped around to see what specific seed cultivars were used in each of the blends.  There is usually a tag with the detailed seed composition somewhere on the bag. When I went out to buy the one I liked, I found that that specific blend was no longer available even though the product name on the bag was the same.  Frustrating!!!  I imagine that the retailers are still trying the produce an equivalent performing product, but it still, that was a frustrating experience.

The first step in the reseeding process is to remove the stiltgrass thatch in the lawn.  This opens up spaces for the new seed and may help remove some undispersed sitltgrass seed.  Since late in the season much of the remaining stiltgrass has had a chance to set seed, this thatch needs to be segregated from regular compost and the regular brush piles.  I have a couple of piles dedicated to stiltgrass so that it does not get mixed up with the regular yard waste and I can monitor it for spreading.  Another option would be to landfill it in thick plastic bags.  You do not want to let the stiltgrass get out and spread its seed.

Late September is when the stiltgrass begins to die back.  The brownish areas are easy to spot.

Once the area was clear of thatch I applied the new seed.  I used the back side of a bow rake to press the seed into the soil.  The nice thing about the conventional turf seeds is that they do not need to be planted deeply.  After sowing, it is necessary to keep the new seed bed moist until the new seedlings are established. I usually try to time my seed sowing with coming rains.  That way I don't need to water it in (I'm really lazy in that way).  Besides the cooler temperatures, autumn is a good time for lawn seeding because it is usually a rainier then too.   I usually see good levels of germination in 10-14 days for the Eco-grass.  This year is working out well (so far).  The soaking rains in early October saturated the soil and I have only needed to add a little additional water to keep the soil moist.

The area between the piles has been (mostly) cleared of stilt grass and is ready for seeding.
I used a leaf rake for this, but a stiff garden rake would have been
more effective for tearing out the stiltgrass plants.

While the standard instructions on the seed bag recommends fertilization at the time of seeding, it is best to do a soil test to determine if added fertilizer is needed.  If you use a mulching mower to return your grass clippings and leaves to the soil your fertilizer needs will be much lower (or non-existent). The risk of over-using fertilizer is that it will stimulate weed growth and that run off of excess nutrients will damage the environment.  Since we are in the Chesapeake watershed I try to use the minimum of fertilizer possible.  That usually means none.  In fact, for the fine fescues fertilization is not recommended.  If fertilization is needed, fall is the best time for cool season grasses.  Spring fertilization will stimulate growth of warm season weeds (and stiltgrass) as well as the cool season grasses.  In the fall only the cool season plants are actively taking up nutrients.

In this full sun area tearing out the stiltgrass exposed a lot of bare ground.
This spot was seeded with the full sun blend.  Just to the back left
 is a full shade area where I planted the Eco-grass mix.

One new thing I learned about tall fescue, Lolium arundinaceum, is that some cultivars are infected with an endophytic fungus that produces loline alkaloids that are toxic to many insects and mammals that feed on the grass.  This endophytic fungus also reduces biodiversity around the infected fescue.  while this is great for the fescue it is bad for the wider plant and animal communities.  The widely used and inexpensive cultivar K-31 has a high rate of infection.  So far I have not been able to find out which cultivar have low infection rates, however this may be more common in southern states.  One way to lower the effects of infected fescue on the environment is to keep it mowed so that it stays in a vegetative state, i.e., not going to seed.  Hopefully its ability to form a good turf and exclude the stiltgrass will outweigh it negative environmental effects.
..

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

A Woodland Find - American Germander

This is the pinkish flower spike that I first noticed.

The other day I was walking along a wooded edge in the backyard bemoaning how much stiltgrass (Mircostegium vimineum) there was to remove and I spotted some pale pink spiky flowers that I had not seen before. Since these flowers looked so tight and upright,  I thought these might have escaped from an old garden rather than being a native plant.

The stems are square with oppositely arranged leaves and the flowers were kind of tubular with a long tongue.  So I figured they were kind of mint (Lamiacea family).  After going through the identification keys in Gleason and Conquist several times and then looking at a lot of pictures on-line, I finally ID'd this plant as American Germander, Teucrium canadense, an actual native species!  In retrospect, a feature that really stands out in germanders is that the 4 stamens stick out above the flower petal(s).  This same arrangement is found on creeping germander, T. chamaedrys, a common garden plant.

Here you can see the unique form of the flower.  The arrow indicates the upright stamens.

10 days later, the flower spike has elongated and blooming is
continuing up the spike.  Maybe another 10 days of bloom.
Here the shape of the toothed leaves is more easily seen

While it is a member of the mint family the leaves are not fragrant and the leaves have a bitter taste (reportedly).  They are not bothered by grazing animals, i.e., deer.  The flowers are frequented by long-tongued bees and hummingbirds.

American Germander grows in moist soils in full to partial sunlight.  Habitats include moist meadows, thickets and along water courses.  The plants I found are on consistently moist soil with about 4 hours of morning sun, in the middle of summer.

Plants spread by rhizomes and will reseed effectively, creating large colonies under favorable conditions.  In a formal garden they would be considered weedy, but in a natural edge with lots of competition they are under control (so far).  I would love for these to push out the stilt grass, but I think they will need my help.  

This clump of American Germander has probably been here for awhile.
I'll make a more concerted effort to clear out the stiltgrass from around here
to give this plant more opportunity to spread.

Just a reminder, Stiltgass will be blooming soon in Maryland so you need to take action soon to keep them from setting seed.  I will continue pulling for now, but come the end of August I will weed whack down as much as I as can reach.  This should  take out the flowers before they can set seed and be late enough in the year to keep flowers from regenerating.  Check out the Mircostegium link above for more information.

Stilt Grass is in Bloom

I have been watching my invasive Japanese stilt grass, Microstegium vimineum, to try and cut it down it before it started blooming.  On Sept. 2 I noticed that just about every plant starting to bloom.  (I am in zone 7a, so if you are in a cooler zone, this may be happening very soon in your area.)  My plan was to weed whack it down just when the flowers were forming so that it would not have time to regrow new flowers and set seed this season.  Since stilt grass is an annual, if I can deplete the seed bank, I should be able to bring it under control.  Several references agree that Microstegium seeds remain viable for up to 7 years.

Japanese Stilt Grass in bloom

One nasty feature of this grass is that it also has a set of self-fertile flowers hidden down in the stem.  These are known as cleistogamous flowers.  So it is necessary to cut these off as well as the upper exposed flowers at the stem tips.

A cleistogamous flower in the stem about 4 inches off the ground.

On Sept 3 I used my gas-powered string trimmer to cut down all the plants I could find growing in the woodland edges.  I made one pass to cut the tops and a second pass closer to the ground to go after the stem flowers.  Cutting the plant in smaller pieces may reduce the likelihood of an fertilized seed from maturing (I sound like a lawyer).  In some areas I found that the stilt grass would bend over, rather than getting cut on the first pass.  So the second low pass was really needed.  Where ever possible I tried to avoid any natives I saw.  These included some Panicled Tick Trefoil, Jumpseed and some, as yet unidentified goldenrods.

For some smaller areas, with other species mixed, in I hand pulled the plants.  Since stilt grass has relatively shallow roots, it comes up more easily than perennial grasses and herbs.

If I can keep this up for a few more years I may be able to eliminate scenes like this:

Stilt grass has filled area to left.  Area to the right is less disturbed
(unmown) and shows less invasion by the stilt grass.