Native Annuals Wrap Up for 2014

For the past 6 or 7 years I have been interested in using native annuals in my landscapes.  By working with species that are adapted to local climate and growing conditions they can behave essentially as highly mobile perennials, moving around the garden by reseeding to find their optimal spots.  In some gardens this could be a problem with too many randomized plants.  Personally, I like the spontaneity of getting something growing unexpectedly.  (If they do get out of hand I can just pull them up or transplant them to a more desirable location.)

This Partridge Pea reached about 3' in height.  They can look gangly
in a manicured garden, but fit well into a naturalistic setting.

This year I started a number of new native annuals from seed.  In addition, I had some reseed from last year.  Here's a rundown on their performance in 2014.  I'll start with the best.

In early to mid summer the best performers were actually plants that had reseeded themselves from 2013:  Partridge Pea (Chamaecrista fasciculata) and American Pennyroyal (Hedeoma pulegioides).  Also the biennial, American Bellflower (Campanulastrum americanum) put on a big show.

The Partridge Pea has spread a little from it original planting.  This is an early transitional species, looking for gaps in the in the ground layer to germinate.  It can be pushed out of a densely planted area if there are no gaps.  

The seedpods of Partridge Pea curl up when they release the seeds.  These could look nice in a flower arrangement.

The American Pennyroyal forms dense low border 9-12" tall.
There is a little Selfheal (Prunella vulgaris) mixed in.

The Pennyroyal grew from a mixture of seed originally planted in spring 2013 and reseeding from plants in that fall.  The main feature of this plant is the strong minty scent that persists in the dried leaves and stems.  The blue flowers are tiny and grow from the leaf axils in late summer.  

These Amercan Bellflowers are at the back of a garden, an appropriate location.
They can get 5-6' tall in a sunny site.

In full sun the American Bellflower can get quite tall and unwieldy.  It grows well in shady spots reaching a more manageable height of only about 3'.  The blue flowers are very attractive to bees. Unfortunately deer seem to like it as well.  Although they left it alone after applying a repellent.  Pruned plants will produce a second flush of flowers.  

The narrow foliage of Plains Coreopsis allows to mix well
with other plantings without blocking the view.

In mid-summer and still continuing was Plains Coreopsis (Coreopsis tinctoria).  I transplanted some spindly seedlings in late June and by mid July they were taking off and blooming.  There was a little deer browsing early on, but this seemed to taper off after a treatment with Bobbex.  The native range of this Coreopsis includes Maryland so I am hoping that these will successfully reseed in the garden.

The two annuals that are still going strong into mid-fall are Yellow Sneezeweed (Helenium amarum) and Scarlet a.k.a. Hummingbird Sage (Salvia coccinea).  

I only got a couple of the sneezeweed to germinate, but once in the ground it took hold and has been blooming strongly since mid-August.  One trick with these is that the tiny seeds that I brought come massed together in few 1/16" spheres.  These need to be broken up and spread over the soil surface to germinate.  I mistakenly treated most of these spheres as seeds and planted them too deep resulting in no germination.  

The bright yellow flowers of this Yellow Sneezeweed do not need to be deadheaded.
Just as well, I hope to get some reseeding from these.

The Salvia germinated easily and after growing in trays for a few weeks were transferred to the garden or into pots.  These plants spent 6-8 weeks growing before they were ready to bloom.  Despite the wait, the blooming has been strong since early August.  This species also does well in pots. but it is kind of tall and you may want some other plants to fill in around the lower leaves.

The tubular flowers of this Salvia did attract our hummingbirds earlier in the season.
At 24-30" it shows up well among other garden plants.

Some other annuals I tried that grew but did not excel this season were Sulfur Cosmos (Cosmos sulphureus), Beach Sunflower (Helianthus debilis 'Pan') and Spanish Flag (Ipomoea lobata). The Cosmos suffered from too much competition from other plants and from being nibbled on by the local fauna.  I expect it would have done better in a more protected location.  The Sunflower germinated well in the garden but was overshadowed by the Annual Sunflower I paired it with.  The Spanish flag matured very late in the season with significant blooming starting in September.  It's blooming well now in late October, but all the supporting plants are fading away.  Spanish Flag is native to Mexico (part of North America); I don't expect to see this one reseed.

The fact that we have not had a real frost yet in our area has really extended the blooming season for these plants.  Some I expect to survive a light frost, while others will be killed immediately.  

I did plant a couple of winter annuals, Texas Bluebonnet (Lupinus texensis) and Miami Mist (Phacelia purshii), out in the garden in late summer.  I'm keeping an eye on them, but have not seen any definitive germination yet.

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