Flirting with Disaster - Growing Aggressive Perennials
Perennials are like men. Some are aloof and demanding (most delphinium), some start handsome and stay that way (sedum ‘Autumn Joy’), some are flashy and fragile (petunias), and some are worth the trouble (roses).
Some plants are bad boys - they aren’t the enemy, but they are aggressive and need to be kept in check. If you invite these plants in, they will try to take over: some will relentlessly self seed and some will send out runners. I don’t find self-seeding to be much of a problem. Newly sprouted seedlings are easy to pull out and the task is unavoidable (anyone who says otherwise is lying), so I don’t mind it. Verbena bonariensis and Tradescantia (spiderwort) are both enthusiastic self-seeders, but they are worth the trouble. When I first grew tradescantia in my garden, their offspring seemed like a blessing, but after a while there was millions of them and their floppiness was annoying. Now I cut the plants down to the ground the second their flowering starts to diminish. That way, their seed production is curtailed and there is room for their later-blooming neighbors to grow.
So I grow aggressive self seeders, but I have generally avoided runners. They are like inviting a guy into your apartment and finding him poking through your medicine cabinet. All perennials will spread sideways and most will produce offshoots, mini clones of themselves near the base, but runners sneak through the soil and pop up somewhere unexpected. If it’s a taller and fast growing plant, these runners can extend pretty far in every direction and the plant becomes a multi-headed hydra. This is how most ground covers spread, but I don’t want a three foot tall ground cover, and the spaces between the offshoots will contain uninvited weeds and the strangled remnants of other garden plants, so it looks like a war zone.
Lately though I have invited a few runners in. Some of them were irresistible, and some of them seemed like they could make themselves at home in some really tough spots. I didn’t keep all of them, and the rejects were hard to eliminate, but three of them made the cut.
Japanese Anemone Anemone hupehensis
I have a spot that is very visible and very difficult to water (near my mailbox where my driveway meets the street). Several plants survived there, but by August everything except the sedum ‘Matrona’ looked malnourished. So I decided to plant a single Japanese anemone there. This is a very attractive plant, with lush, robust foliage that’s about a foot high, and beautiful pink flowers that rise three feet on slender stems. It starts blooming in late August, and I am a sucker for late bloomers. The foliage manages to be lush and lacy at the same time, and it has great fall color, and butterflies love it.
At first it was charming and well behaved, and it took a couple of years before its growth began to hint at its aggressive spreading. I decided to give it a bit of room, but no more. Whenever it gets to close to the edge of its area, I dig up as much of it as I can (the roots run deep and they are a bit scary looking). A few springs ago I decided that it was too aggressive and I dug the whole thing out - at least I thought I did. I divided it and put two good sized chunks back in the same spot. By late July, it was clear that there was plenty left because there were five good sized plants. It wasn’t a problem, but it did let me know that if I wanted to eradicate it, it would take a superhuman effort.
I love this plant and I have planted it throughout my garden, and I even bought the white version to compliment it. It’s pretty well behaved, but it’s growing in dry spots and I have to keep it in line.
Bee Balm Monarda didyma 'Jacob Cline'
I grow this for the hummingbirds. There are hummingbirds in my area, but you have to make a serious effort to see them. They like sun and red flowers, and they are extremely skittish. I grow this plant in full sun near my front porch, and every now and then when I’m relaxing on the porch I will see a hummingbird. Other plants attract them as well, but this is the only plant I found with a long bloom season that’s as visible to hummingbirds as it is to me.
‘Jacob Cline’ is a cultivar of a native plant, and it has interesting flowers that are a great shade of red. Honestly, I don’t love the plant, but I do love the red and I love the hummingbirds. Honestly, I don’t find it that hard to keep it in bounds, but maybe I find it easier to brutalize it because I don’t love it. It seems that it takes those who love it for granted and loves those who abuse it. I’ve known a lot of guys like that.
Obedient Plant (Physostegia virginiana)
The first time I ever heard anything about this plant was from a gardener who was talking about how aggressive it is. I was immediately scared off and I wouldn’t grow it for years.
I very recently changed my mind. When I started gardening, native plants weren’t a thing. I was a botany geek, so I learned about it, but the fact that it grew in nearby meadows wasn’t a point in its favor. A couple of years ago I rescued a pot of them from our Plant Sale refuse. I wasn’t sure what it was so I didn’t plant it, and when it leafed out more I realized that I had one of the most infamous aggressive plants there was. At first I was going to throw it out (it was too aggressive to risk the compost heap!) but I didn't get around to it. During the hottest part of the summer, I decided to plant some perennials in a 45 degree narrow strip that was in full sun and difficult to water (I love. a challenge!). I remembered that I had this plant and I decided to put it in. You see, I wan’t convinced that anything would survive, and I realized that the plant was native, and I certainly wasn’t going to plant it anywhere else.
So far so good. It is doing well with the delsperma and sedum, and it started blooming about a week ago. The flowers are very pretty pale pink spikes and they make great cut flowers (florists gave this plant its nickname because the flowers are malleable). We will see how it goes, but if it becomes too aggressive I may cede the entire strip to it.
So I would recommend flirting with aggressive plants, just make sure that your flirting doesn’t have to lead to a commitment, and just because you have a relationship with a plant doesn’t mean you have to tolerate his extended family.