Mint is not only fragrant and flavorful but also very easy to grow. The hardest part of raising mint may be keeping it from taking over your garden altogether, crowding out more delicate plants. In this article, we’ll review several ways to grow mint in your garden while keeping it under control.
The Growing Habit of Mint & Why You Need to Control It
Mint is a perennial, so it keeps growing year after year. It will grow in a variety of conditions, thriving both in full sun and in part shade. It’s also an aggressive spreader. Mint plants send out runners both above and below ground, and their clumps multiply rapidly in size.
If you want to keep having other plants in your herb garden—or your vegetable garden if you’re using mint as a companion there, you’ll need to contain mint’s sprawl.
If you want to grow several different varieties of mint you may want to plant them well apart and also keep them contained. Rosemary Gladstar warns in Medicinal Herbs: A Beginner’s Guide that mints readily interbreed with each other. The resulting hybrids may have worse flavor or weaker medicinal properties than their parents.
5 Ways to Keep Mint from Spreading
There are many ways to keep your mint contained. Here are a few suggestions to get you started.
1. Frequent Digging And Dividing Of Mint Plants
Now that my family has a fairly large herb garden, we plant unconfined mint in part of it. When the mint begins to bulge out of its allotted area we dig it up, divide it, give large chunks away to neighbors, and replant enough for our own use.
You’ll want to divide your mint periodically anyway so that it doesn’t grow woody and straggly. Plant sharing can also be an easy and pleasant form of community building.
Some plants are finicky about just when you divide them. Mint isn’t. I dig up chunks of it to give to neighbors throughout the growing season. I fill in the holes with compost since mint thrives in rich soil.
2. Growing Mint In Pots
You can grow mint in pots to prevent it from spreading by underground runners. (This won’t however, stop it from spreading when stems reach over the edges of the pot and trail along the ground. See Strategy 5 below.) Strawberry mint is smaller and less spreading than its cousins and said to be particularly adapted to growing in small containers. But most mints will grow in large containers.
- Start with a container at least 12 inches deep. Clay pots are recommended when submerging your containers in the ground, because they are porous and ‘breathe” as plastic pots can’t.
- Make sure there are holes in the bottom and/or low on the sides of the container.
- Prepare your growing medium. Don’t use straight garden soil in a pot, as this will get compacted. One Extension article recommends using standard potting mix and adding compost for fertility when growing plants in containers. Use no more than 1 part compost to 3 parts potting mix.
- Set your mint plant into the pot.
- Put the pot in a sunny spot and keep it well watered.
Rodale’s Garden Problem Solver recommends dividing and re-potting container-grown mint every year.
3. Growing In Bottomless Containers
When my family had very limited garden space we set our mint plants out in circles of wide-diameter PVC pipe, buried several inches in the soil of the herb garden, and rising three or four inches above the ground. This allowed the roots to grow deep but kept the underground and aboveground runners contained.
The Hamilton County Soil & Water Conservation District recommends the bottomless containers need to be buried at least 18” deep. However, I don’t think our PVC pipes went that far down.
The Arizona Extension office offers another interesting variation. They suggest planting mint in clay chimney flue liners sunk into the ground at different depths, and they say that different mints could be planted in adjacent flue liners whose tops reach different heights so the different plants don’t sprawl into each other.
Drainage is less of a concern in bottomless containers than in pots. The Arizona Extension describes filling containers with soil, not potting mix. That’s what I remember my mother doing when I was a child and we grew our mint inside a PVC pipe.
4. Planting Mint Along Garden Borders
We have a bed of mint between the wall of the building we live in and the mowed lawn. Thyme escapes into the lawn and grows enthusiastically (and we let it, since it smells good and is more drought-tolerant than grass). Taller-growing mint is more easily discouraged by frequent mowing. The mint plants fill their bed but have nowhere else to spread.
We grow mint’s similarly spreading relative lemon balm around the bases of the oak trees in our lawn. Some gardeners plant mint along sidewalk edges or in other spaces where they simply can’t spread beyond certain bounds.
This strategy takes less time and effort than growing in containers. You’ll still need to divide and thin your plants at intervals so they don’t get woody and die out. And if your mint border is reasonably close to your other gardens, your other plants can still benefit from the pollinators attracted by the blossoming mint.
But if you want to use mint to repel insects from other garden plants you may need to set your mint in among those other plants and keep it in containers.
5. Pruning And Supporting Mint Plants To Keep Them Contained
This is an adjunct to most of the strategies above. Even if you plant mint inside containers, tall stems of mint will flop over the sides of the containers, trail along the ground, grow roots, escape and spread.
If you want to keep your mint confined, either use supports to keep your mint stems upright or trim them back when they begin to flop.
Sometimes my mother supports her plants with a simple cylinder of chicken or turkey wire. Sometimes she has my brother make a more attractive support with twig legs wound round by a length of grapevine.
Some types of mint are leggier and likelier to flop and root than others. Strawberry mint may stay in its containers better than most other types.
How Will You Control Mint In Your Garden?
There are many reasons to grow mint—for flavor, for fragrance, for health, for loveliness, for pollination. With a little time and effort, you can grow robust mint plants and also grow other things nearby without a constant struggle to keep your mint plants off them.
These are some ideas to get you started. You may come up with better ideas of your own.