One common problem that happens to most gardeners at some point in their life is having an aggressive or invasive plant spread all over their yard. While it’s true that all plants have the ability to spread via seed, there is another method some plants have which is to spread via underground rhizome or stolon. We can stop plant rhizomes from spreading by creating a physical barrier between your flower and the surrounding vegetation. And I’ll show you how to stop rhizomes in this guide with pictures.
My method I created works great. I have successfully used it on many species of aggressive plants such as Bee Balm, Obedient Plant, Whorled Milkweed, and even Pale Leaf Sunflower.
What are Rhizome Roots?
Rhizome Roots are small fleshy roots that grow horizontally underground and send up new stems/plants. Certain species will use rhizome roots to expand their area and beat out competition. Also known as runners, rhizomes can expand swiftly at great distance and speed and crowd out other plants.
How Fast can Rhizomes Spread?
Depending on species, rhizomes can grow and spread quite rapidly. To provide context, I had a small clump of a perennial sunflower that was about 6″ diameter at the end of the first growing season. During the summer/fall/winter it was secretly sending out rhizomes in all directions. I had no idea this was occurring, as no new shoots were visible above ground.
But the following Spring, I was quite surprised to find a solid mat of shoots that was 2-3′ diameter (1 m).
I took no action on my new ‘carpet’ of sunflowers. I guess I just forgot, or thought that perhaps it wouldn’t accelerate it’s expansion. Well, I was wrong and at the start of the 3rd year, the area had expanded to roughly 8′ diameter (2.5 m). I had new sprouts coming up everywhere – in between other plants, all over the place!
So, after spending about 2 hours carefully separating and removing shoots from other plant root systems, I had cleared the area. But, I still wanted to keep this plant but not have it spread all over. So what did I do?
Process to stop plants spreading via Rhizomes
I’m going to show you with pictures how I created a physical barrier to stop my flowers from sending out Rhizome Roots. This method works, and is long term as plastic doesn’t degrade.
Materials required
- Old plastic flower pot, bucket that is 10-12″ tall (30 cm) and at least 6″ diameter (15 cm)
- Landscape fabric
- Knife
- Shovel
Guide to stop plant rhizome roots from spreading
1 – Add drain holes to the pot if they are not already there.
2 – Line the flower pot with landscape fabric. If you want the plant to be 100% contained, line the entire pot!
3 – Dig a hole that is large enough to accommodate the pot for both diameter and depth.
4 – Place your pot in the hole, and back-fill dirt inside/around the pot. Make sure a small portion of the upper lip is above the ground/mulch.
5 – Plant your flower/rhizome root in the pot, and water it in.
6 – Monitor your site to make sure there are no rhizome roots left in the soil in the area, sending out new shoots.
There is one other important point regarding this method. Depending on where you plant the container, the plant may need more supplemental water than if it normally would. This is because water can only transfer via osmosis through the landscape fabric / drainage hole interface. Thus, there will be less moisture available to the plant.
What I’ve found is that if the plant is in full sun all day, especially in the hot afternoon, then I will need to provide supplemental water. If it gets sun from morning up until lunchtime, then it generally doesn’t need it. Also, the larger the container, the less water it will need.
How effective is this method at stopping rhizomes from spreading?
I have used this method, or some variation of it on multiple species of plants in my yard for years. Below is a list of species I have done this with, and the year I started. Please note, that for Obedient Plant and Bee Balm I didn’t fully line the pot, but only the drain holes. After a couple years I did have a single rhizome escape from a Bee Balm plant. However, that is the only failure I’ve experienced with this method. If you try it and it works – do me a favor and call it the GrowitBuildit method 🙂
- Bee Balm (2021)
- Common Ironweed (2022)
- Missouri Ironweed (2022)
- Pale-Leaf Sunflower (2021)
- Obedient Plant (2021)
- Whorled Milkweed (2022)
Planting in a container with the bottom cut out doesn’t work (most the time)
Seeing my article on this topic, you may be interested in trying to take a short cut and just plant your aggressive flowers in a container with the bottom cut out. While it is true that most rhizomes are shallow, usually in the top four inches, not all are. In fact, I tried doing that very method on Pale-Leaf Sunflower back in 2020….and it failed miserably. By the next year I had new sprouts next to the container (see pic below).
The bottom line is, despite what some well-known sources may say, planting in a container with the bottom cut out will not stop most rhizome producing plants (in my experience). However, I have found success in doing that in exactly one type of spreader – Mountain Mint. I have contained several mountain mint species for several years now (and Virginia Mountain Mint for many years) by planting them in a container with the bottom cut out. So, you may find other species that this does work for – however just be sure you know the risks!
Video guide
This is a video I recently released documenting this method over multiple years. Have a look – it should hopefully give you confidence to try this method!
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