Eat Your Foes!
What if the best way to control invasive plants was… dinner? Our latest Space Invaders installment explores edible invasives across the Mid-Atlantic, how they impact ecosystems, and how to remove them one bite at a time!
Space Invaders: Eat your foes!
In this special edition of Space Invaders, we look at three nonnative invasives (and one plot twist!) ubiquitous throughout the Mid-Atlantic region that have an unusual solution… voracious consumption.
Taking a walk in our parks and along the trail, it’s shiso, stinging nettle, common dandelions, and garlic mustard everywhere. May is the season for the four to be lushly growing, colonizing the edges of woods, roadsides, ditches, and garden beds all over. Now is the time to make your move… and grab your harvest basket! If you don't want these invasive plants taking over in the landscape, we fully encourage folks to get their 5 a day and eat these rampant bullies.
Garlic Mustard
Commonly found in great swathes along the edges of tree lines, garlic mustard (Alliaria petiolata) is a biennial. In its first year, it forms a rosette of bold, rounded leaves, and the next year, bolts with white flowers along long stems and heart-shaped, serrate foliage. This Eurasian species was introduced with colonists in the 1800s for its use as an herbal remedy and food and spread from there. In North America’s woodlands, large colonies of garlic mustard take hold and choke out native species. The roots emit an allelopathic chemical that inhibits the germination of native seedlings and suppresses native soil fungi. By its mere presence, it drastically alters the landscape it inhabits, discouraging the emergence of native tree saplings and crowding out the understory canopy, eventually forming an aggressive monoculture.
The good news is that all parts of the plant, from the root to the flower to the seed, are edible. This is the one time we want to eat something out of existence. So, let’s get to it. A word of warning: it’s best consumed when young, as older plants contain a buildup of phytotoxins that require special preparation for consumption. Harvesting for the table is best done in early spring to early summer, as the plants are first emerging. From the leaves, you can make zingy sauces, marinades, dips, and salads, while the roots are delicious additions to stir fry. As you are out in the woods gathering this invasive plant for dinner, be sure to dig up all of its roots and remove and bag any of its friends nearby, even if you aren’t going to eat them. It takes 5-7 years of consistent invasive plant removal at a site to exhaust the garlic mustard seedbed. As long as you consistently harvest the plants before they go to seed each year, an area can be garlic mustard-free after a few years’ concentrated dinner harvests.
Dandelions
The first bouquet of flowers you probably gifted to a parent when you were a child, the common dandelion (Taraxacum officinale) originated from Eurasia and more than likely arrived in North America with European colonists bringing seeds to grow familiar herbal remedies on these shores. Summarily loathed for its presence in pristine swathes of fescue lawn, dandelions have been much maligned in recent years. Sprayed, dug, and ripped out, the common dandelion has already endured such villainy that we're hesitant to heap more on its head. In an effort to flip the story on its head, pollinator enthusiasts in Europe have led the charge to lionize this humble herbaceous perennial for its early-season flowering, which supports bees waking up from their winter slumber. ‘No-Mow May’ gets touted all over social media. Let the dandelions flower. But as an introduced nonnative in North America that carpets wherever its fluffy seeds can land, it will take a mile if you give it an inch. While ‘No Mow May’ is fine in Europe where common dandelion originates, it's not a good plan here. Introduced invasive plant species overwhelm and outcompete native flora, reducing biodiversity and making the ecosystem more fragile, as one species replaces many in the same space and does not support the broader food web as the diverse indigenous flora did. While North America has its own endemic species of dandelion, most notably a fine form of horned dandelion growing in the mountains west of the Rockies into Canada, the ones we encounter in our suburban landscapes in the Mid Atlantic are likely the Eurasian species.
For individuals fortunate enough to come across dandelions in areas that do not receive chemical treatments (i.e., plants close to farm fields, golf courses, treated lawns), all parts of the dandelion are edible. The roots can be boiled like a parsnip or dried, roasted, and ground like chicory as a non-caffeinated coffee substitute. The leaves are bitter, said to aid digestion, and are useful to add to a salad. The flowers can be used as an edible garnish or made into flower jelly or even dandelion wine. Dig up the entire plant to enjoy for a boost to your plate.
Shiso
For those who want the foliage color of a purple basil or coleus but want it to be delicious and drought-tolerant and shrugs off high humidity, then… You can understand how this plant became so prevalent in our disturbed natural areas. It’s one of those pesky invasive plants that are useful, durable, tasty, and pretty, which means it’ll keep being planted. Also known as perilla or beefsteak plant, Perilla frutescens originates from the Himalayas and Southeast Asia and is a beloved component of Asian cuisine. It is identified by its opposite, ovate, serrated leaves that grow quickly and range in color from green to purple/red. As a mint family member, you know this plant is gonna grow, and grow it does, which is the problem. As an annual herb, Shiso matures quickly and yields a thousand seeds per plant. The sheer volume of plants produced is the issue. It escapes cultivation by wind dispersal and quickly creates smothering monocultures in disturbed landscapes, where a number of our best pollinator-supporting native plants also opportunistically grow. It is a particular problem in warmer areas and is listed as invasive in North Carolina, Tennessee, Kentucky, and West Virginia.
Thankfully, shiso is easy to remove from an area with consistent hand weeding as long as the plant is removed before it goes to seed. As this plant is a major component of various cuisines, if planted in a kitchen garden, remove flower stalks as they appear to prevent seed development and dispersal into wild lands. If you’re removing Shiso plants from a landscape, go ahead and make use of the foliage. There are numerous recipes featuring the leaves as a wrap, cooked down as a side dish, in stir-fries, or in dozens of other applications. Whatever isn’t consumed, bag it up and remove it from the landscape. Be aware that Perilla frutescens contain phytotoxins that are toxic to livestock, especially as these chemicals build up in the plants from August to October. Remove shiso from areas where ruminants are housed. For those removing the plants, consistent bare-handed contact with the leaves can cause contact dermatitis. We encourage wearing gloves when removing P. frutescens.
Stinging Nettle - plot twist, is it invasive?
This one is a fun one! Stinging nettle (Urtica dioica) is a perennial rhizomatous forb found near riparian areas. It’s an upright plant growing 2’-6’ tall with slender stems and hairy, toothed leaves. The flower clusters are arranged at the axils of the upper leaves. What was originally labeled as yet another Eurasian invasive plant brought to North America that we need to give the boot, the species Urtica dioica (stinging nettle), was found to be circumglobal in temperate regions, with subspecies present in North America, Europe, Asia, and North Africa. According to the USDA, the American stinging nettle subspecies Urtica dioica subsp. gracilis is prevalent throughout “most of Canada, and to the East and Midwest, American stinging nettle occurs as far south as Virginia, Missouri, and Kansas; while in the West, it occurs south along the coast to central California and south in the Rocky Mountains to Mexico. European stinging nettle, or Urtica dioica subsp. dioica, occurs primarily along the Atlantic Coast from Newfoundland south to Georgia and Alabama.” So, realistically, it’s very challenging to tell the difference between the European subspecies in the Mid-Atlantic and our native North American variety.
With that in mind, it’s not a plant that necessarily needs to get evicted from your landscape due to its disruption of the local ecosystem. However, you may just want to remove it from a place near people or pets because of the, you know, unbelievably uncomfortable stinging sensation that brushing past the fine hairs gives you, akin to the feeling of fiberglass. Not only that, but its flowers are a major contributor to summer hay fever allergies.
Now, why would anyone want this plant? While it’s been observed to not be especially useful to our native pollinators besides as habitat, stinging nettle is shockingly nutritious for the rest of us. Between the dense delivery of vitamins A and C, phenolic compounds, and antioxidants when cooked, stinging nettle is also one of the best providers of protein from wild plants, containing up to 40% protein by dry weight in its leaves. Iceberg lettuce simply can’t compete. For those wondering how you even eat a plant that stings you, it can be cut and harvested as young plants in spring while you’re wearing gloves and long sleeves. Then the leaves can be neutralized by blanching, boiling, or drying for use in soups, pestos, or teas.
How to get rid of them
For those who do not have the option of eating these invasives, other removal options include:
Physical removal: dig up the entire plant, root and all, in the early growing season. To reduce the chance of spreading, remove plant material before it goes to seed. If the plant does not have seeds, it can be left to wither in the sun before being added to a compost heap. If it has seeds, place it carefully on the fire or into a bag, then remove it from the site.
Fire: Flame weeding can be very effective on recently emerged shoots in early spring. The more mature the plant, with a deeper root system, the more likely it is to resprout from the roots after a fire. Flame works best on young, succulent seedlings early in the season.
Smother: using plastic sheeting, carpet, cardboard, or old rugs, lay down the chosen smothering tool and anchor it to the ground. Be sure to overlap material edges to prevent light and moisture from entering. Depending on the climate, amount of sunlight, and heat the area receives, we recommend leaving the smothering materials on the invasive material for an entire summer or up to a full year before removing.
Ruminants: Garlic mustard and dandelions are safe forage for goats and other ruminants if animal rotation is part of a land management and invasive plant removal strategy. Stinging nettle is a nutritious forage, but cattle avoid it when fresh due to its stinging hairs; however, it can be used as silage after it is dried and fermented. Shiso is toxic to livestock and should not be managed with ruminants.
Mechanical: Mowing is not recommended for perennial stinging nettle, as it will encourage rhizomes to spread and colonize the area. Mowing annual shiso plants before it goes to flower is effective at controlling spread and exhausting the seed bank. Repeated tilling in the spring or early summer is an effective tool for all four plants as long as it is performed before the plants go to flower/ripen seed. Mechanical methods will require multiple passes to be effective and to exhaust the seedbed.
Chemical: Apply a systemic herbicide. Broad-spectrum herbicides such as glyphosate can be effective, as can broadleaf selective herbicides such as 2,4-D. Follow the herbicide label instructions for application information. Do not consume plant material that has been treated with herbicides.
Take Away
We like to think that there’s not much in life that sitting down together to a good meal can’t fix. Controlling invasive garlic mustard, dandelion, shiso, and stinging nettle is a great addition to that list. Unlike other editions of Space Invaders, these common invasive plants can be removed, one forkful at a time. From salad to pesto to stir fry to tea, we can sip, chew, and savor our way out of this problem.
