The Stiltgrass Wars

Beating back non-native invasive plants

Prologue

Sweat drenched clothes. Mosquito bitten. Gnat filled eyes. The trials of summer gardening in the mid-Atlantic. I blink the sweat and gnat bits out of my eyes and stare out at the disaster of my garden. I’d spent weeks in the early summer mulling over what to do about the sprawl of stilt grass which chokes out any hope of native plants thriving. But as August ticked along, and stilt grass germination loomed, the time for indecision had passed. If I let it go to seed, next year the coverage will be thicker and cover a greater area. Not only does it form a thick mat and prevent natives from growing, it is ugly. And I’m not alone, stilt grass is considered one of the most damaging of non-native invasives on the east coast of the US. Every time I look at it, it seems to say “I’m coming for you. I shall invade all your flower beds, your lawn, your woods, your very soul.”

Chapter 1 Why we’re at war

When I tell friends I’m at war with a non-native invasive plant, the reaction is often quite negative, and even aggressive. Maybe this is because many of us recognize that we ourselves are non-natives and we’re repelled by the association of non-native with invasive. Some people will argue over the definition of native, pointing out that all plants have evolved - nothing has been here forever - at some level no plants are natives. Others will emphatically state that the world is changing and plant communities must evolve too. While I appreciate these points, there is a critical distinction at play here. I’m at war with invasive non-native plants. Invasive plants tend to spread rapidly and choke out the native flowers and grasses. They destroy the habitats that feed and shelter our wildlife. With so much of our wildlife threatened by habitat loss, pollution and climate change, the added pressure of agressive invasives is too much for many species.

Japanese stilt grass, otherwise known as Microstegium vimineum, is one the most invasive of plants. It is thought to have arrived in the US in 1919 as a packing material for Chinese porcelain. It has since spread from Florida to New York to Texas. In my own garden its in every flower bed, under every shrub, and dominates my wildflower meadow and my little orchard. It’s even making its way into the woodland in a wave about 30 feet deep so far.

Chapter 2 Misconceptions

I can’t say I wasn’t warned. Soon after I arrived at my new abode, Susan, a fellow native plant enthusiast, told me to pull up this funny looking grass with the silver vein running down the center of its leaf. The faint silver line is defining characteristic of the grass.

But to me it was just another of the grasses I didn’t know and I dismissed her comment. I thought she must be slightly mad to be concerned over a little old grass like that. Any individual grass stalk is easy enough to pull out.

So I started cutting flower beds out of the lawn. Great swaths of flower beds. Some I wood chipped and some I didn’t. Of the many different areas I planted up, only two have survived relatively stiltgrass free. The first is a perennial bed just by the house. This bed was watered regularly during its first summer and the plants are big and fill the space. There is little space for the stilt grass here and the sprinkling of invasives that do grow there are easy enough to pull out The other mostly stilt grass free place is where we laid down cardboard and then covered the cardboard with about 4 inches of wood chips. I’ve been disappointed in this area because none of the seeds I’ve sown and few of the tiny plants I’ve planted there making it to plant hood - but it is just this inhospitable nature that has prevented the stiltgrass from flourishing. Right now, it’s a huge relief to have one fewer area to have to de-stilt and certainly a lesson in the advantages of trying different ways to garden.

Chapter 3 Reports from the fronts

I am in a race with the little nasties to get them cut before they germinate in the coming weeks - typically in September in Pennsylvania and mid-August in New Jersey. It has not been pretty. We don’t want to start removing the stiltgrass any earlier because then other weeds can germinate and set seed and we’d have to remove it all again. And if we weedwack or mow too early, stilt grass can still set seed. So, in effort to time it as close as possible as to ‘just before the seeds set’, I’ve spent 4 hours every day for the past two weeks pulling, weed wacking, mowing and trying to pray stiltgrass out of my garden. In the flower beds and woodchopper areas, I have been pulling up each plant by hand. In the areas where the stiltgrass is not so long, I have been mowing and collecting the cuttings. From these two methods alone I have filled over 10 big garbage cans with the cuttings and pullings.

But in the more wild areas, my mini-orchard and my wildflower meadow, the stiltgrass has grown up to about 2 and 1/2 feet. Worse yet, it has formed a dense mat so that the lawn mower can’t get through. In fact, the grass gets its name from the buttress like roots, or stilts, it sends out from its stalk that help the plant to stand up. In these areas I’ve had to weed wack with the stimmer. This leaves an ugly carpet of cuttings on the ground. But I have decided to leave this till spring to prevent other weeds from growing there. I raked out the wildflower meadow this spring and that worked a treat - we got loads of spring and early summer flowers. I’m also devising a plan to hide the view of the ugly carpet of dead grasses from my living room by planting a native hedge and perhaps putting up an archway.

Aside from the unpleasing visual result and the hours of feeding the mosquitos, it’s been emotionally difficult to cut down so much grass. Moths, butterflies, and crickets fled my whirling strings and blades of destruction. And sadly, I also scared one of those sweet Dekay snakes and a couple of toads. I’m normally so patient with my weeding and I tap my way through along with a stick to send the critters elsewhere before I pull out weeds. But I had no time for this in the War of the Stiltgrass. To give the now homeless critters a place to retreat to, I left as much native ground cover as I could, mostly violets, and went out this morning to hand pull stiltgrass from them.

Painfully, I know I’ll have to repeat this every August for a few years until the seed bank of stiltgrass becomes unviable. But it must be done if I have any hope of inviting in more natives.

Chapter 4 Battle plans

• Know thine enemy and be relentless. Pull stiltgrass whenever I’m weeding anywhere and whenever I can stand to rip some out.

• Plant thickly. This means putting in aggressive native ground cover like Packera aurea (Golden ragwort) into the edges of the woodland and under shrubs. But it also leads to the conclusion: DON’T DIG ANY MORE FLOWER BEDS. Seriously, I’d advise you to not bite off more than you can weed. That is the pathway to madness I tell you.

• Deep mulching is our friend. In many areas, arborists will be only too happy to bring you a truckload of wood chips for free. I may even lay down some papers to suppress weeds around the base of the trees and shrubs, if I’m really being kind to myself.

• Beware of the lawn. Stiltgrass can grow and set seed in a regularly trimmed lawn by setting seed at a very low height. I’m thinking the most ecologically friendly solution to this nightmare is to have the mower at a high setting until late August, or just until the seeds start emerging, and then to do a low cut and collect the trimmings.

Chapter 5. Epilogue

With season one of the Stiltgrass Wars under my belt, I can confirm I’ve won on several fronts but am anxious I’ve lost the woodland battle and that next years invasion could be worse. With a more nuanced and informed battle plan ready for next years campaign, I’m hopeful that I’ll make greater headway in providing native habitats for my local critters.