Invasive Plants: Confine or Avoid!

As a gardener, you don’t want invasive plants in your yard that drive you nuts and waste your precious time. Sure they may look great for a season or two…then they act like they are possessed and take over the garden and lawn. Sometimes you don’t plant these thugs – they just mysteriously drift over from a neighbors. Unfortunately, invasive plants are probably on the shelf at your favorite nursery too. Some do just fine confined to a pot (like mint), others are best avoided altogether for sanity’s sake.

The good news is that it’s easy to bypass these garden hooligans in favor of plants that are just as pretty and better behaved. Do a little research before you buy. Take the advice of seasoned gardeners…they’ve been there, done that and can offer excellent tips. Identifying invasive or aggressive species is key to controlling them.

If you already have an invasive plant, get rid of it or control its spread. Don’t allow it to set seed. Birds eat the berries and can excrete the seeds miles away. Some seeds remain viable for years or even decades. Talk about hardy!

Here’s why invasive plants are so successful and hard to conquer:

1) They tend to grow and mature rapidly
2) Most spread quickly and can flower and/or set seed over a long period of time
3) These tough guys have few known diseases or insects to provide control over their spread
4) Aggressive plants thrive in many habitats and are difficult to control

These types of plants are often attractive, but don’t play well with their more well mannered plant neighbors. Actually that’s not an entirely accurate statement. Initially many aggressive spreaders seem just fine, filling in nicely and covering empty spaces in our garden plots. Later on when they exceed their boundaries, overwhelm neighboring plants, and require endless trimming and yanking out…do the consequences become clear.

Experience is an excellent teacher and I’ve learned the hard way that some plants are better off away from the veggie garden or flower garden.

The following plants are invasive and best grown in containers or confined areas:

1. Mint – (from Catnip to Spearmint) These flowering and fragrant herbs can easily take over a yard. Even if you are meticulous at cutting before the flowers spread their seed, this perennial will still be invasive. The best place to plant this is in a pot away from the garden. I’m growing spearmint in a container on our patio.

2. Oregano – Every bit as invasive as mint. This family also includes Lavender, but I have never personally had a problem with that spreading out of control. If you want to grow oregano, plant it in a pot.

3. Lemon Balm – This fragrant herb loves to spread. I’m growing it in a container where it’s thriving and not overtaking anything.

4. Horseradish – A sturdy root crop that is so easy to grow you may regret ever planting it…if you plant in the ground that is. It is very tenacious and will continue to find a way to come up in unwanted areas of your garden. I would suggest planting it in a large container, and placing that on a stone slab. Otherwise the roots will find their way out the pot’s drainage holes and into the dirt.

How To Confine Invasive Plants

Invasive herbs can be kept in check very easily simply by growing them in individual containers, or a confined space in the garden. Container gardening for invasive herbs can be done one of two ways. You can plant individual herbs into individual containers and leave them aboveground, or you can recess the containers into the ground.

If you decide to recess your containers in the ground, it is best to use simple undecorated containers made of plastic. Do not recess the invasive herbs in the same container that you purchased them in though. Use a container that is a size or two larger to ensure that your plants have room to grow and mature.

Planting a Container

Planting a Container

To recess a container for invasive herbs, dig a hole large enough for the entire pot to fit into, leaving the lip (top portion) of the container sticking out approximately one or two inches. Be sure that your container has drainage holes. Fill the bottom of the container with gravel or Styrofoam pellets to allow proper drainage of the pot. Add potting soil and then plant your herb into the buried container.

The following perennials are known to be invasive in Zone 5:

Loosestrife – both yellow and purple love to spread like crazy.
Nepeta – can quickly take over a garden.
Lily of the Valley – I haven’t grown it, but have heard horror stories about the invasive properties.
Lamb’s Ear – Love the fuzzy texture and color, but beware it can be aggressive. It’s gone haywire in a neighbor’s yard popping up in the lawn.
English Ivy – English ivy seems to be the worst of the vining plants. If you want to see ivy-covered walls, go watch a Cubs game…which is another waste of time in my opinion lol.
Vinca species/periwinkle – At our last house I fought with this. I prefer using vinca in container arrangments.
Creeping charlie – just dreadful! Wanders everywhere and has the toughest roots I’ve ever seen. It invaded our garden once and I don’t know where it came from. I definitely didn’t plant this scourge of gardeners.

Some states are planning to ban these plants from retail markets due to their invasive habits:

Burning Bush
Japanese Barberry
Norway Maple

I’ve not had any problems with burning bush and love the gorgeous fall color the shrub provides. Barberry – not a big fan. We had several inherited shrubs in our yard in Wisconsin. I couldn’t stand the thorns. Norway Maple – never grew one, but I’ve heard they can get out of hand. The roots can grow under sidewalks and driveways causing major headaches.

In summary, invasive plants or aggressive garden plants are best grown in containers, confined to an area, or avoided altogether. These bullies of the garden world can be impossible to tame with their unworldly aggressive underground spread or prolific self-seeding. Consider yourself forewarned and tread carefully…

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Category: Container Gardening, Perennials, Zone Information