Are Any Of These Invasive Species Growing in Your Garden?
Some plants just don’t play well with others. They might look pretty at first, but invasive species often spread aggressively, crowding out native plants and disrupting local ecosystems. The tricky part is, many of them are sold in garden centers. You might not even realize that you’re growing an invasive species until it’s too late. But knowing what they are is the first step to managing them, so it’s a good thing that you clicked on this article! Here are eight invasive species that you might spot growing in your own yard, why they’re a problem, and what you can do to remove them before they take over.
Japanese Knotweed
This plant can grow through cracks in pavement and even damage foundations. It spreads quickly through rhizomes (horizontal underground stems), making it hard to fully remove. If you see tall bamboo-like stems with heart-shaped leaves, take action early. Cutting it down repeatedly can weaken it, but you’ll find yourself chopping away at it for several years. And if you compost the cuttings, Japanese knotweed can regrow. Instead, what you should do to get rid of the problem is bag and dispose of the plant with yard waste. In severe cases, you may need to call in a professional to dig out the roots or apply targeted herbicides. But the sooner you start, the better your chances are of keeping it from spreading further.
Purple Loosestrife
The bright purple spikes of flowers on purple loosestrife plants are beautiful, but so bad for the environment. It’s mainly because this plant outcompetes native wetland species that wildlife depend on to survive. And once it’s established, it’s really hard to control because it spreads by seed and root fragments. To remove it, pull or dig up plants before they set seed, making sure to get the entire root system out. And wear gloves, as the stems can be tough on your skin. Make sure that you don’t leave pulled plants on the ground either, because they can re-root in moist soil. Once they’re out of your garden, dispose of purple loosestrife plants in a way that ensures the seeds and fragments won’t wash into waterways, where they can quickly spread downstream.
English Ivy
English ivy can look charming on walls and fences, but it can choke trees, damage brickwork, and smother garden beds, (which nobody wants). To remove it, cut the stems at the base and carefully peel them away from trees or structures, as pulling too hard can damage tree bark or mortar that the ivy is growing on. On the ground, pull up the roots by hand or use a spade to dig them up, working in small sections. Persistence is key here, as new shoots can grow from any leftover roots you might have missed. Covering the area with mulch or black plastic after removing the plant can block sunlight and help stop the plant from coming back over the next season.
Garlic Mustard
Garlic mustard is a fast-spreading biennial herb that releases chemicals into the soil to suppress native plants. Not friendly! Pulling it up by hand works well, especially when the soil is moist, but be sure that you get the entire root out. It’s important to act before it flowers and sets seed, which usually happens in late spring. If seeds have formed, carefully bag the plants to keep from spreading them. Never compost these plants after you pull them, because the seeds can survive and sprout later. Keeping a close eye on the area where the plant grew for several years is important, as new plants can sprout from any seeds left in the soil.
Himalayan Balsam
With its pink, orchid-like flowers, Himalayan balsam is a pretty plant but highly invasive. Its seed pods burst when touched, flinging seeds for several feet all around the plant. To get rid of these plants, you have to pull or dig plants before the seed pods mature, which usually happens in midsummer. Because it has shallow roots, it’s easy to pull Himalayan balsam up by hand, especially in damp soil. Dispose of plants away from waterways to keep seeds from spreading downstream. Make sure to double-check the same area for new plant growth throughout the season, as missed plants can still produce seeds. But, replacing Himalayan balsam with non-invasive flowering plants can help keep it from creeping back into your garden.
Yellow Flag Iris
This tall, showy iris thrives in wet areas, but forms dense mats of vegetation that block out other plants from getting the nutrients they need. When you go to remove it, wear gloves because its sap can irritate skin. If you want it gone for good, dig out the rhizomes completely and take care not to break them, as even small fragments can regrow into a whole plant. If digging isn’t possible, cutting the leaves and flowers repeatedly throughout the season can weaken the plant to a manageable amount over time. Bag and dispose of all plant material, as any loose seeds can float and travel far in water. Replanting the area where the iris was with native wetland species will help keep the space healthy and cut down on the chances of this plant returning.
Crown Vetch
Crown vetch was once used for controlling erosion, but when it grows in gardens, it spreads aggressively through creeping stems that lay down roots wherever they touch the ground. Digging out the roots works fine, but it may take several seasons to fully get rid of it. Regular mowing or cutting before the crown vetch flowers can help stop seed production and weaken the plant to make it more manageable. Avoid tilling the surrounding soil, as it can break roots into pieces and the pieces will regrow into new plants. Once the plant is fully cleared, planting dense, non-invasive groundcovers in the same spot can help block sunlight and cut down on the chances of crown vetch coming back.
Tree of Heaven
This fast-growing tree produces masses of seeds and sends up root sprouts far from the main trunk. It’s tricky to deal with too, as cutting it down without treating the stump can actually make it spread even faster. The most effective method is a cut-and-treat approach: cut the tree and immediately apply an appropriate herbicide to the stump to prevent it from regrowing. Digging out young trees, roots and all, can work if they’re small. But removing seedlings before they establish a deep root system is the easiest long-term solution. And make sure to regularly check your yard for new sprouts, especially after removal.
Keeping Your Garden Balanced
Invasive plants aren’t bad because they’re not native, they’re bad because they take more than their share of the nutrients, pushing out the native plants. Once you know what to look for, you can make better choices and protect the balance in your yard. Replacing invasive species with native species doesn’t just help the environment, it often results in less maintenance and healthier soil for you. With a little persistence and the right techniques, you can keep your garden safe from the threat of invasive species.