Popular Methods for Controlling Invasive Plants: Do They Really Work?
Over the years gardeners have tried numerous methods to control the spread of an aggressive or invasive plant. But do they really work? Here's a hard look at some of those popular methods:
Not every plant that your find in a nursery or garden centre is well-behaved. Retailers often sell plants that many consider problematic or invasive.
Why sell them then?
Not everyone would agree on what constitutes a "problem" plant. Based on my own personal struggles, I happen to think that Goutweed, Aegopodium podagraria 'variegatum' is pure evil, but I know at least one friend who thinks that it has nice variegated foliage and likes to have this plant in his garden.
For me a problem plant is not just aggressive, it is also a plant that is hard to remove where unwanted. Vigorous perennials like Goutweed can send out roots that spread underground in many directions. Eradicating it can be very difficult. Even if you dig out the main plant, any roots segments you miss are capable of producing a new plant.
Other plants like False Lamium, Lamium galeobdolon 'Florentinum' (read more about different types of Lamium here) send out runners above the ground (similar to those of a strawberry plant) that take root and create new offspring.
In a somewhat similar fashion some vines, as well as climbing up, will send out runners along the surface of the ground. New plants will naturally layer along the length of the stem.
Let's take a look at some methods to control the spread of an aggressive plant. Here's a look at some of the most popular methods:
Method 1: Use an aggressive plant in a container planting.
This works, but even so, I advise you to do this with a little caution. Trailing plants like Creeping Jenny look great in a container planting, but keep an eye on it. In a shallow pot, it can cascade right to the ground and take root.
I almost had this happen with False Lamium 'Variegatum'. It trails nicely, so planted it in the window box under my kitchen window. A few weeks later, I noticed its yellow flowers had begun to set seed. The little black seeds were in danger of dropping into the garden below, so I trimmed the flowers off. Then a month later, I noticed that the runners, which made such a pleasing cascade over the edges of the window box, had reached down almost 4 ft to the ground and were about to take root. I was both dismayed and impressed with the plants determination to create offspring.
See the False Lamium 'Variegatum' trailing out of an urn above? Notice it has almost reached the ground. Trim it back and it would be fine for the rest of the gardening season.
Method 2: Put an invasive plant into a plant pot and submerge the pot in the ground.
Personally, I have found this doesn't work very well. Trailing plants will skip over the rim of the buried pot and take off into the rest of the garden (I had this happen with Oregano).
Plants with deep roots can also sneak out the drainage hole in the bottom a buried pot.
I tried planting Artemisia 'Silver King' in a buried pot only to watch it layer itself into the surrounding garden (layering occurs when an upright stem bends down to the ground and takes root).
Method 3: Create a deep edge or trench around an island bed that contains an aggressive plant. This works to a degree, but you would really want to make sure the edge is deep and wide, so an invader can't jump across the divide. The only other worry might the possibility of the the plant self-seeding into other areas.
Method 4: Plant a spreader into a raised bed.
Where there is a botanical will, there is a way. In the picture above, you can see that Gooseneck Loosestrife (white flowers) has spread from the raised bed to the ground below.
I've also heard horror stories where the roots of really vigorous plants like Bamboo have cracked through concrete and escaped into the surrounding landscape.
Bottom line: know what you're planting and how it is likely to behave.
Too often gardeners are impatient to fill up their flowerbeds and choose a plant that will spread quickly. Patience is a virtue, especially when it comes to gardening.
After years of battling Goutweed in our front garden, I decided to take drastic measures to get rid of it once and for all. Click the link below to find out how I did it.
Click the link below to find out how I did it.
Want more details about this and other DIY projects? Check out my blog post!
Published May 21st, 2017 1:34 PM
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