Stiltgrass has taken over Saltsburg yard
Question: We live in Saltsburg in a wooded area. The small backyard and our wooded areas are being overrun by a wild grass that resembles oats. I have attached a photo for your review. Thank you and hoping you can help.
Answer: The plant in your photograph is Japanese stiltgrass (Microstegium vimineum), a non-native invasive plant that is running rampant across many parts of the eastern U.S.
It's an Asian native that is adaptable to low-light areas and moist soils. It thrives in disturbed areas and is often found in wooded sites, along roadsides, in meadows, on streamside banks, and in just about any other shaded area. It can also take over lawns and garden beds, if left unchecked.
Japanese stiltgrass grows between 1 and 3 feet in height and is very fast spreading. It is an annual grass that spreads primarily by seed, though if a stem falls against the ground, it will take root and spread that way as well. The plant dies back in the fall, when cold weather arrives, but before it does, it drops seeds that will go on to germinate the following spring. Unfortunately, Japanese stiltgrass produces a lot of seeds and a small colony can spread very rapidly. As a result, especially in woodland areas, it outcompetes and displaces many native plant communities.
Japanese stiltgrass found its way to North America when it was used as a packing material in a shipment of goods from Asia in the early 1900s. It has since spread across much of the Southeastern U.S. and is now said to be found in over half of our 50 states.
The distinctive appearance of this plant make it fairly easy to identify. It looks much like a miniature bamboo, with thin stems and opposite, lance-shaped leaves. Identifying Japanese stiltgrass is made easier by looking for a small stripe of silvery hairs down the center rib of each upper leaf surface. Pairs of slender flower stalks grow from each stem in late summer through early fall. Seeds are dropped shortly after.
The seeds of Japanese stiltgrass remain viable for several years, and they spread easily on clothing and animal fur. So even if you manage to rid your landscape of the existing plants, you'll have to deal with new seedlings for several years after.
To control Japanese stiltgrass, the most important step is never allowing the plants to drop seed. For small patches of this grass, hand pull the plants and then lay down a thick layer of mulch to bury any dropped seeds.
For larger areas, mow the plants to the ground in early August, just before they develop flowers, to keep them from producing any seeds.
As stated earlier, this is an annual grass, so it will die back completely in the winter and your goal from there on out should be to keep any new seedlings from growing. You can use an organic pre-emergent weed killer made from corn gluten meal to limit seed germination, but be aware that it will keep all seeds from germinating, not just those from the stiltgrass. Other options are hand hoeing, pulling, or weed whacking seedlings as they emerge and then covering the area with a layer of mulch.
Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio with Doug Oster. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden: A Natural Approach to Pest Control” and “Good Bug, Bad Bug.” Her website is jessicawalliser.com.
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