We have all heard of invasive plants, most of them fall in the category of weeds. However, some invasive varieties fool us. Favorite herbs, flowers and vines that we love can also get out of control. Many of these are also sold at nurseries and, when that is the case, we think that they are perfectly fine to plant in our gardens…until they behave badly and try to take over.
Some of these bad boys even trick us because they start out in an orderly fashion and provide us with perfumed flowers, edible and medicinal herbs and even treasured vegetables. But then, they show their ugly side and start bullying other plants by taking over.
HOW PLANTS BECOME INVASIVE
There are a few things that sets invasive plants apart from their counterparts and makes them so hard to kill.
*They tend to grow and mature rapidly.
*Most of them can flower quickly and can flower and set seed over a long period of time.
*Most of them have few natural enemies or natural diseases that will kill them.
*They thrive in many habitats.
*They are attractive with either their flowers or fragrances which makes us want to plant them.
When I learned to paint, I painted violets on a clock base because they were so pretty. Little did I know back then that they were also very invasive. I started one little clump in my flower garden and since then they have spread to many areas of the yard. They also grow in the crown of my rose bushes. I never would have guessed that something so pretty, tiny and dainty could be such a persistent grower!
Another species that surprised me was morning glories. I have always planted the heavenly blue ones and then a friend gave me a start of some smaller dark purple ones to try. That was certainly a mistake. They not only took over my entire fence, but also killed off the heavenly blue ones. Their seed can be spread by the wind and by birds and they get a start in farmers’ fields. Once there, they grow up corn stalks and wreak havoc on farmers’ equipment when the vines wrap around the moving parts.
Some other surprising invaders are:
*Mint. All varieties from catnip to spearmint, once they get started there is no stopping them. Even when they are started as only a tiny clump in the garden, they can easily take over a yard.
*Oregano. This herb is as bad as mint for taking over spaces. Although not considered an invasive species, this family also includes lavender.
*Lemon balm. Who doesn’t love the fresh smell of this enticing herb? Its fragrance is what makes it so attractive in gardens, however it also loves to spread and take over.
*Horseradish. Once you plant this hardy root crop…and even when you are the lucky recipient of this via other ways than planting it, you will have it forever. It is impossible when digging it to grind into horseradish to get all the pieces of root and one little piece left behind is all it takes to form a new plant. When planted in a pot, its roots will find its way into the soil through the drainage holes in the pot.
*Loosestrife. This voracious grower has invaded wetlands throughout North America. It is a fast-spreading plant that grows primarily in wetlands. A relative of the primrose family, it can grow up to 10 feet tall either in a couple feet of water or on dry shore near the water line.
*Nepeta. Commonly known as catnip, these are easy to grow, long-lived, resistant to deer and rabbits and irresistible to cats. You may be doing your cat a favor by planting this, but certainly not yourself.
*Lilly of the Valley. These fragrant, white-flowered plants with small bell-shaped flowers are attractive to use as borders around flower gardens. However, they spread quickly and are hard to get rid of because the plants grow so close together it is hard to pull the roots out. They are even growing in the cracks between my rocks.
*Iris. These tall beauties may not be considered invasive but they do spread and it is literally impossible to pull all of their rhizomes from the soil.
*Lamb’s Ear. This fuzzy, textured plant is sometimes referred to as a weed because, once they get a foot hold, they pop up all over the lawn.
*English Ivy. This may very well be the worst culprit of all vining plants. It will easily engulf the outsides of buildings and everything else it grows near. Perhaps the only other vine that is more invasive is kudzu. In China, kudzu is used to treat alcoholism but here it is known as “the plant that ate the South” because it literally grows on everything in the southern United States.
*Creeping Charlie. Its name suits this plant since wherever it gets a foothold, it tends to creep…and creep…and creep.
*Garlic and chives. Grown for their pungent flavor in many dishes, you will never be short on it because even a couple missed flower heads will give life to hundreds of new plants.
*Fennel. Its seeds taste like anise and its leaves are flavored like dill. Fennel has actually invaded farm fields in California and Virginia.
*German chamomile. This herb literally self-sows anywhere. In Boulder, CO, it grows in the cracks of sidewalks instead of crabgrass.
*St. John’s wort. Valued as a mood lifter, it can quickly cause depression if let go unchecked.
*Tansy. It repels flies, ants and other pests until it becomes a pest itself.
*Yarrow. Known to heal bruises, burns, wounds and sores, it multiplies without any help.
*Calendula. These bright, yellow flowered plants cheer up any flower garden until you can’t stop their spread.
*Wisteria. This vine was introduced from China in 1816. Although one of the most popular flowering vines, it can displace native species and have even killed sizable trees.
*Strawberries. This beloved fruit sends out runners, that left unchecked will take up a bigger place in your garden than you had ever intended.
*Bamboo. Don’t even think of starting it. Technically a giant grass, once it is started it is nearly impossible to kill. Its sprouts in spring can grow 12 inches in a day and its roots can tunnel out 20 feet.
*Bradford pear. These line many small town streets and are a sight to behold in spring when they bloom. However, they have creeped into fields and along roadsides until they have become pests in some areas.
*Butterfly bush. This beloved fragrant flower that provides nectar for butterflies is actually a noxious weed in Oregon and Washington. The butterfly larvae can’t eat its nectar so it doesn’t support the entire life cycle of the butterfly and displaces native plants that do support them.
WHERE YOU WANT SOME INVASIVE SPECIES
Some invasive species like myrtle, vinca and other ground cover are actually encouraged to take over trouble spots and keep weeds at bay. These are great for planting around buildings and rock gardens because when they creep into the lawn, they can just be mowed off and managed easily. Because they cover empty spaces, these plants become attractive.
So, what do you do when some of your favorite plants are invasive? You don’t have to give them up, just don’t let them run free. Instead of planting them directly in your gardens, put them in a container where they will be constrained. The container can either set on top of the ground or be buried in the ground.
Badly behaved plants can still be a welcome addition to your landscape…you just have to show them who is boss!