Weed Watch: Japanese stiltgrass

Japanese stiltgrass (Microstegium vimineum) is a non-native, invasive, annual grass. It has lance like leaves with a silvery stripe down the center, arranged alternately on a thin, wiry stem somewhat like a very miniature bamboo. It normally is 2-3 feet tall at maturity in late summer with seed heads at the top of each stem.  

Stiltgrass was probably introduced into this country as packing material in shipments of goods from China in the early 1900’s. Since then it has made itself at home in open woodlands, paths, roadsides and of course lawns and flowerbeds.

Stiltgrass has the ability to form dense stands that crowd out and smother native and desired plants. The stems root at the nodes, allowing a single plant to advance across the ground.  While stiltgrass is an annual and the parent plant dies in winter, it creates an enormous amount of seed and quickly builds up a bank of seeds in the soil. Each plant can produce up to 1000 seeds and they remain viable in the soil up to 5 years. The key to control is preventing new seed production and preventing germination of the existing bank of seeds.

The plants are shallow rooted and can be pulled by hand. Plants should be removed before mid-August when the seed matures.  Cutting or breaking the plant stems earlier in the season may stimulate them to create and drop seed early, so try to remove each plant completely. The process of weeding may disturb soil and expose more seeds from the seed bank, encouraging new weeds. Mulching directly after weeding will help prevent germination of new seeds. Planting desirable plants densely to leave less open garden area may also help prevent stiltgrass germination.

Plants in a mowed lawn will still create seeds at the lower height. If possible, wait until just before the seed matures to cut large stands of stiltgrass so there is not enough time before winter cold for seed development.

There are some options for chemical control of stiltgrass.  This article from Penn State Extension describes those options.

Want a little more information? Here are some links:

Penn State Extension – Controlling Japanese Stiltgrass in Your Garden

PA Dept. of Conservation and Natural Resources: Japanese Stilt Grass PDF

The Humane Gardener – How to Fight Plants with Plants

Weed Watch – Lesser Celandine

Lesser Celandine may have cheerful yellow flowers, but don’t let it fool you. This is an aggressive, non-native thug that is wreaking havoc in our natural landscapes (not to mention front yards, back yards, flowerbeds and lawns).

Lesser Celandine (known as Ficaria verna but sometimes still listed as Ranunculus ficaria ) was brought from Europe in the 1860’s as an ornamental plant and escaped cultivation. The plant has shiny, dark green, kidney shaped leaves and bright yellow flowers. It typically emerges in late January to early February.

Because it emerges so early and creates a very dense mat of leaves, it smothers many of our native spring wild flowers by blocking out light, air and growing space before they can even get started. Our native insects are then deprived of the pollen and nectar they need early in the season.

Lesser Celandine is an ephemeral and is usually dormant by late June. This can cause problems in wetlands because other plants have been snuffed out so there is not as much vegetation left to prevent soil erosion in late season flood events.

Lesser Celandine is a very vigorous spreader, mainly through underground tubers and bulblets attached to the leaf stems. It prefers moist soil, but can survive in drier areas. It can colonize an area very quickly.

The tubers and bulblets can be spread by animals, by flooding and even by well meaning gardeners. It is often seen along stream banks where it has been spread by water flow.

Managing Lesser Celandine is very difficult. Small infestations can be weeded out, but you must remove all the tubers and bulblets. Weeding can actually spread the weed if you are not careful. To help contain the spread, keep in mind:

• Never put removed Lesser Celandine in the compost.
• Do not pile it on the ground or rake it up, put it directly in a disposal container. You may need to dispose of some soil along with the tubers to ensure you have removed it all.
• Mowing Lesser Celandine can fling the small bulblets into other sections of the lawn.
• When the plant is dormant, its easy to move the tubers from one part of the garden to another when transplanting other plants.

It is possible to eliminate Lesser Celandine with herbicides, but the window of opportunity is small. Here are a few references that discuss the use of herbicides.

• Pennsylvania Department of Natural Resources Lesser Celandine fact sheet
• Brandywine Conservancy Invasive Species Spotlight: Lesser celandine
• Plant Conservation Alliance Fact Sheet – Lesser Celandine