Tuesday, October 13, 2015

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.

No comments: