Japanese stilt grass, an annual non-native plant that is invading many U.S. regions, is entering its final maturity stage in Connecticut landscapes. Tiny flowering units that will form the seeds for next year’s crop are emerging from each stalk. In Connecticut the time to tend to Japanese stilt grass is NOW!
As an annual, Japanese stilt grass (Microstegium vimineum) germinates, grows, flowers and seeds in a single growing season. Each tiny flowering unit will generally produce 100 new seeds. In three to five years Japanese stilt grass can completely overtake an area. The tiny stilt grass seeds easily spread in flowing water and strong winds, on passing creatures, and with any soil disturbance.
One key component in controlling Japanese stilt grass is preventing as many plants as possible from going to seed. Each of the 100 or so seeds produced by each plant can remain viable in the soil for seven years. This produces a Japanese stilt grass seed bank that can sprout to life in any disturbed soil for up to seven years after it is deposited.
In Connecticut, Japanese stilt grass generally germinates during late spring – late-May through mid-June. It flowers any time from mid-to late August through early September, and produces seeds from September through frost.
Because of its prolific spreading attributes, it’s easy to feel overwhelmed by a Japanese stilt grass. It will overtake your gardens, woodlands, and lawn if left unmanaged. Stilt grass management in home landscapes takes time and vigilance. It helps to know that each Japanese stilt grass plant that is prevented from going to seed will limit about 100 more plants over the next seven years.
Since my home landscape is in a Japanese stilt grass bull’s-eye zone, I’ve read as much as possible about it, observed how the plant grows along roadsides and on area properties, and asked experts for their management advice. Management requires a multi-pronged approach that depends on the size of the Japanese stilt grass stand and the area in which it is found.
Large stands of Japanese stilt grass, such as those along roadside edges, should be mowed while mature. In Connecticut that is now – early September – when plants are just forming flowering stalks but have yet to develop seeds. Remember: each Japanese stilt grass plant that is prevented from going to seed will limit about 100 more plants over the next seven years. Leave cut vegetation to dry in place since any raking or disturbance of the soil will encourage growth of stilt grass seeds laying in wait in the soil.
Smaller stilt grass infestations can be hand-pulled by spreading your fingers through the base of the plant and gently pulling upward. With mature plants out, any smaller Japanese stilt grass plants are easier to see and pull. When pulling, try to get as many roots as possible without disturbing the soil too much.
Three years ago we first discovered maturing stilt grass growing among native grasses and ferns along a woodland edge of our property. We weed-whacked the area flat during late August, left all vegetation to dry through September, then piled about 6 inches of wood chips to cover the 6×8 foot area.
The following June, July, August and September I watched for and pulled every stilt grass seedling and plant from the mulched area. But we also noticed maturing stilt grass in adjoining areas that must have come from previously unnoticed seeding plants. We weed whacked these areas in early September, before the stilt-grass produced seeds, and left cut vegetation to dry.
This year, 2013, is the third season of managing stilt grass in this area. Fewer plants sprouted this year than in previous years. During June and July, I was able to hand pull young stilt grass plants from the mulched area which is now nicely re-establishing with native ferns, grasses and wildflowers. In the areas without mulch (seen in the photo at the beginning of this post) we allowed this year’s stilt grass to grow through August and hand-pulled mature plants just yesterday.
Some close-ups of Japanese stilt grass show how the smaller plants, easily hidden among ferns and other native vegetation, will grow to become more visible.
The leaves of Japanese stilt grass often develop a white stripe along the central vein. Flowering parts emerge from the top of each stalk.
This photo shows a small portion of the wood-chip mulched area as well as the heavily infested area after we finished pulling Japanese stilt grass. Hiding amongst mature Japanese stilt grass plants were wildflowers, grasses, ferns and moss.
Japanese stilt grass will grow in sun or shade and in dry or moist soil. To keep it from establishing in the native woods around our cultivated landscape, I take a stilt grass management walk through these areas in June, July, August, September, and October. It seems most likely to first appear under trees and where soil has been disturbed, but it will grow most anywhere. I pull young plants and leave them to dry and die. Any plants found in late August or later – those that potentially have flowering stalks – go into a bucket for disposal into the trash.
Any stilt grass plants found growing in my perennial beds also go into the trash for disposal. To be safe, do not place Japanese stilt grass or any other invasive plant into compost.
Japanese stilt grass control in the lawn is a whole different topic. Because Japanese stilt grass is an annual, its entire existence centers around producing seeds. Therefore, Japanese stilt grass plants that are mowed regularly along with lawn grasses will flower and seed even when cut to lawn height.
Yes, those mini stilt grass plants – the wider leaves with the white stripe – will often produce seed even at this height.
We currently pull out any small, individual plants found growing in our lawn areas. Unfortunately, stilt grass has also invaded a 20×50 foot area of lawn grass on our property. Since the area is a bit large for hand pulling, my husband resorted to torching it. Using a propane-fueled torch, he burned the tops of the stilt-grass – and all other grass. Since stilt grass is an annual, the torched plants should not regrow. We hope the perennial lawn grasses will regrow, and we are currently watching the area to see if they will. If not, we will overseed to re-establish a good thick lawn which will should help minimize future germination of new stilt grass plants from seeds still in the soil. Watch for a future post to see how this experiment works.
Controlling Japanese stilt grass has become a critical part of our landscape management plan. If it is growing on or near your property, you’ll have to adopt similar measures to prevent it from overtaking your landscape.
Remember: Each Japanese stilt grass plant that is prevented from going to seed will limit about 100 more plants over the next seven years.
Read UConn’s advice for good background information on Japanese stilt grass.
The Invasive Plant Atlas of New England has more information and color photos of Japanese stilt grass.