Horsetail has great architectural features that makes it an attractive choice for designers, but it spreads aggressively by underground rhizomes and is difficult to eradicate where it is unwanted.
Occasionally gardeners may introduce a plant into their yard’s flower beds that initially seemed attractive and innocent, only to later discover they have a garden thug or bully. It’s the kind of plant that will race to occupy every available inch of soil, crowding out meeker and less aggressive plants, even to the point of becoming the dominant plant in the area.
Experienced gardeners know what I am talking about, and many will have stories about what it took to eradicate the bully (assuming they were indeed successful). Interestingly enough, for some gardeners the same plant might be more restrained – perhaps a difference in soil, or the amount of care given by the gardener in the form of water and fertilizer.
Some garden thugs are prolific reseeders, while others spread by underground stems called rhizomes. Think of Bermuda grass which has underground stems that sprout new shoots as they grow. Reseeders can be dealt with by diligently removing seed heads before they mature. That can be a problem if the plant produces continuous flushes of blooms, like many summer perennials. Another option is to maintain a thick layer of mulch to prevent the seeds from germinating. Just be aware that if you have some desirable, mannerly reseeders in the same bed, they too will be suppressed.
Plants that spread aggressively by rhizomes must be contained if you do not want them spreading beyond a specific area. That can be a problem because some can grow very deeply in the soil, deeper than any barrier you might try to install to constrain their spread.
The following are just a few notorious plants that you should beware of. You may even like some that I will mention, and wonder how I could classify them as thugs and bullies. This goes back to the adage, “the right plant for the right location”. You may have a hostile spot totally surrounded by asphalt and concrete, where little else will grow, much less thrive except one of these aggressive types. The bottom line is, learn all you can about the plants you are about to purchase or accept as gifts from a friend. This is true whether the plant could be termed aggressive or invasive, or not. The informed gardener is a much more successful gardener. With this post, I am not getting into the invasive species issue – we’ll look at that in a future post. For now, refer to my co-worker Chad Gulley’s post from earlier this year.
Houttuynia cordata, better known as Chameleon plant, or hootenanny for those trying to pronounce the tongue twisting botanical name, is one that Master Gardeners in the IDEA Garden are currently battling. It is a groundcover with an attractive mix of colors in the leaves, and it thrives in moist areas. It is extremely aggressive, with roots penetrating deeply into the soil, and even has found its way to the top of a 2 foot retaining wall surrounding this concrete-enclosed bed. We had to remove all other desirable plants and make multiple herbicide applications over a period of months to try to totally kill this plant, because if we leave any, it will return to plague us.
Horsetail (Equisetum) – This plant is a true survivor, and is commonly found fossils. It grows as tall, green jointed stems, and is typically found in aquatic or boggy areas, but it is extremely aggressive, and difficult to control once out of bounds. Sinking it in a pot with holes is not the answer as the rhizomes will make their way through the drainage holes and grow into the surrounding area. Use with extreme caution where it cannot escape its confines.
Not all bamboo’s are clumping, like this mannerly Bambusa multiplex. Too many have a running (even racing) habit that spread with abandon and is difficult to control or keep in bounds.
Bamboo. Not all bamboo is invasive and troublesome, but it seems the more common ones are the running types. This is where investigation and research will save future headaches. There are clumping varieties which expand incrementally over the years, and are very attractive. There is an example of this type in the IDEA Garden on the northern border. The clumpers are the types to get if you do not want it taking over your yard and then the neighborhood.
Ribbon grass (seen here with Louisiana iris in a bog planting) is an attractive short grass that spreads aggressively, and is best used where it can be contained.
Bamboo is in the grass family, and there are other grasses that can be problematic. Another running (by rhizomes) grass is ribbon grass (Phalaris arundinacea picta), that grows 2 to 3 feet tall with thin blades with white and pink highlights. It runs and spreads with abandon, and is another thug Master Gardeners got rid of in the IDEA Garden due to its unneighborly traits.
Inland sea oats is an attractive, perennial native grass adapted to woodland, low-light settings, but is a prolific reseeder.
Inland or Northern Sea Oats (Chasmanthium latifolium) is an attractive woodland perennial grass of the eastern United States. It is clumping grass, so what’s the problem? It is those very attractive seedheads that look just like the seaoats on the Gulf Coast. If you cut them off before they shatter and fall off of the plant in late winter to start lots of little ones, then there is no problem. Just be forwarned that it does self-sow prolifically, and will spread well beyond its original location.
Not a true petunia, Mexican petunia spreads by rhizomes and exploding seedpods
Mexican petunia (Ruellia brittoniana) is another reseeding perennial that also spreads extensively by rhizomes. It blooms throughout the warm season, and when the seedpods dry, they explode, sending the seeds hurtling away to find a spot to begin a new plant. I have seen this plant used effectively in parking lot islands and the strip between the street and sidewalk where often little else will grow. The related Dwarf Ruellia, on the other hand, does not sucker nearly as badly, though it can and does reseed. It has been named as a Texas Superstar.
Dwarf Mexican petunia is a more mannerly form of Mexican petunia. This is the pink version of the more common blue Ruellia.
The list could go on and on. Many plants that spread may be members of a larger group that are better-behaved, and some plants may be exceptions to reseeders and spreaders, such ones with sterile flowers. As mentioned earlier, when planted in the right place with knowledge of its growth habit, a thug could be the right plant for that location. When considering a plant, find out its name, and then research its growth habit so you won’t be surprised or frustrated later on.
