If only this line ended differently! Alas, it does not. Plants horribly out of their context are often the fastest-growing plants in our landscapes. No holds barred, they are not subject to the diseases, pests, and growing conditions of the place to which they are native, which always kept their growth in check before. There, they were in balance with their ecosystem. Here, they are like good farm boys from Iowa suddenly on a wild weekend in NYC with no parents, and a wallet full of money. You can hope everything's going to be okay, but chances are, those boys are going to let loose in ways they never would at home.
But, one major difference is that the farm boys can return to Iowa and repair their reputations, leaving NYC only slightly more chaotic than when they first arrived, while the invasive plants, with their unruly behavior, are here to stay. And just what is unruly behavior in a plant? If they germinate even a little more quickly, or grow taller a little more quickly than the native plants around them, the battle is over, and the invasives have won. And this is exactly why many invasives have earned themselves that name. Invasives displace native plants, along with the insects which prefer to feed or reproduce on native plants. To add insult to injury, they sometimes also release chemicals that actively kill other plants around them.
Controlling invasive plants is a major part of establishing - or protecting - natives in your home landscape. This is an ongoing task, because as soon as you think it's under control, some lovely birds - which you are attracting to your home with all of your native plants - will "deposit" seeds of some unwanted invasives, which will then germinate, and you'll start the cycle all over again.
But the situation will get better over time. Start with taking out all of the plants that are of fruiting age, because this is where the problems are starting. Then work your way down to the less mature plants, which are definitely taking up space, but are probably not going anywhere fast if they're not themselves setting seed. After a while, you'll be down to just the plants that are germinating every year, and these are easier to pull up.
How to get rid of the invasive trees and shrubs, like the aforementioned Tree of Heaven, my personal arch nemesis? Cutting them down will take away their ability to produce seed that season, but they'll resprout. You will need to kill the plant in order to keep it from coming back with a vengeance. Here are some methods to try for the larger trees and shrubs:
- You could cover the stump with a layer of thick black plastic, well-attached to the ground, and keep that in place for a year, and see if that works.
- You could keep on cutting off all of the sprouts from the stump or stem, as soon as they come out - eventually this will wear the plant out, and it will give up, but this may take a long time.
- You could try to pull out the entire stump and root mass with a big truck and a chain - although with some plants, if you leave behind even small pieces of root, those will resprout.
- Or, you could paint the newly-cut stems or stumps with a concentrated solution of glyphosate (aka the active ingredient in Round-up), to keep them from re-sprouting.
Of course, many invasives can be controlled by pulling them up when they are small, or simply cutting off their flowers, if they are annuals (like garlic mustard). These should always be the measures to turn to first, when they are options.
But - what if you don't know what's in your yard? Find out! The DCNR has some great tools to help homeowners identify, and learn how to control, many varieties of invasive plants. Here's a link to one of my favorites - a tutorial that includes pictures and control methods for each invasive variety:
http://www.dcnr.state.pa.us/Forestry/invasivetutorial/List.htm
Take heart! There's no way your property has more invasive plants than mine does, so if you need a sympathetic ear, you've got one here. Good luck!
