Mint is a wonderful culinary herb and a beautiful leafy green plant that’s very attractive in the home garden. It’s also a prolific spreader. To keep mint under control, it’s best to grow it in a pot. Learn how to transplant mint, whether from the nursery pot, last year’s pot (which it’s outgrown), or even dug up from the ground. Also learn about its extraordinary root system.
One of the rites of passage for beginning herb gardeners is to make the mistake of planting a crazy, propagating plant that quickly grows out of control and takes over the garden. Lol.
My mistake was lemon balm, a distant relative of (but in the same family as) today’s subject. Lemon balm spreads aggressively through both its root system and its surprisingly hardy and portable seeds. Such a mess, I cannot tell you. It took over everything, smothering even purslane and dandelions in its path. I still find lemon balm sprouts in odd places in the yard to this very day.
But I’m here now so you can learn from me: don’t set yourself up for future headaches by planting something invasive like mint in the ground. There are completely sensible and legitimate reasons for letting mint run wild – if you’re an herbalist, for example – but for most backyard gardens, you’ll want to keep it on a tight leash and transplant mint to a container.
Mint is a perennial herb in the Lamiaceae family, of which there are well over 7,000 varieties, from small house plants to large shrubs. Most of what you’ll find for purchase at the local garden center are aromatic mints with lovely and interesting flavors that are prized in the kitchen: the common spearmint and peppermint, of course, but also lemon, ginger, chocolate, pineapple, orange, licorice, grapefruit, lavender, and more.
I’m currently growing peppermint, spearmint, and ginger mint in my container garden – see photo above.
All of these amazing plants share one thing in common: they grow fast, and they spread far and wide via their elaborate and aggressive root systems.
A Look At Mint’s Incredible Root System
The root systems of mint have two primary features:
- fine, fibrous tendrils that drop vertically from the plant to intake nutrition from the soil, as well as anchor the mint plant in place; and,
- rhizomes, which are a type of plant stem that grows underground and can extend horizontally for great distances, producing offshoots that break the soil surface to create a new plant.
The roots themselves are nothing to shout about, as they produce the typical root ball that we’re all familiar with. But the rhizomes are something else entirely.
They’re clearly identifiable as thick stems (when not dusty with dirt, that is – see a nice shot of them in the photo below) and grow aggressively outward from the plant in a web, with the sole intent of creating new mint plants. And they’re very, very good at it.
The photo above is a one-year-old peppermint plant. When I bought this plant last year, I left it in the nursery pot and set it in some soil on a raised garden bench for the summer. Those rhizomes are just one year’s growth, winding around the interior of the pot. Imagine if those rhizomes had been free to roam the yard!
I hope the photo above drives home the advantage of growing mint in a pot. Even if you’re an avid cook or a connoisseur of mint tea or mojitos, it would be quite the feat to use up all of the plant’s leaves in one season. The average home gardener does not need an ever-more-sprawling plot of mint.
How to Transplant Mint
Mint is its best, most behaved self when kept in a pot. Even if you decide it must go in the ground, my advice is to plant it in a pot, and then plant the pot in the ground – and dig up and transplant to a larger pot in subsequent years as needed. The sole purpose is always to keep control of those rhizomes.
When to transplant mint
It’s fairly easily to know when a mint plant needs to move to larger pot. In most growing zones in the U.S., mint will die back in the winter (store the pot in an unheated garage or shed, or at least protected from wind outside). It will, in fact, look quite distressingly dead. But, hold steady.
In the spring, when the temperatures regularly warm above 55ºF, watch for mint’s revival. You’ll begin to see tiny leaves and shoots emerge from among the dead stems.
Leave the plant to do its thing for a bit. If the weather is dry, give it a light watering now and then.
Once the growth begins in earnest, you’ll see a pattern emerge. If the green growth is consistent across the surface of the soil, the plant doesn’t really need repotting.
But if the center of the pot has no new growth, with new green sprouts ringing the edges, it definitely needs to be moved to a larger pot. The rhizomes beneath the surface drive the new season’s new growth, and if the sprouts appear only around the edges of the pot, that means the rhizomes have grown outward from the center of the plant – as is their imperative to do, to spread outward – and are running around the walls of the pot (remember the photo above) because they have no room to do anything else.
Select a pot
Mint’s root ball is not particularly large nor deep, so you don’t need to step up to a significantly larger container to transplant mint. I usually just go one size up (which, in the U.S., pots sizes usually come in 2″ increments), acknowledging that the plant might need repotting again next year. Make sure the pot has a drainage hole.
Choose a pot that’s large enough for the plant to sit in comfortably, with room below for a fresh soil base of an inch or so, and enough space around the sides to fill in with new soil.
If the root ball is particularly compacted, you can gently break up the roots a bit by splitting the ball in half from the bottom up. I normally don’t, though. I also leave the rhizomes alone, even when they look quite squooshed.
If the pot’s drainage hole is more than a 1/2″ in diameter, place a small rock, a square of screen, or even a coffee filter, over the hole, to prevent soil from crumbling out.
Add a layer of soil to the bottom of the pot, and then set the plant in the middle. Add soil around the sides evenly so that the plant remains centered. Continue adding soil up to the level of the original surface. Press the edges down to firm the soil, and water well.
Trim away dead stems
With the plant set in the pot, you can now trim away the previous season’s dead stems and branches.
Use sharp scissors or needle-nose pruners to clip away the dead stems. You can tell dead stems from live because in the spring the woody stems will have no new green growth at any of the nodes along their length. And they’ll be quite brittle. Snip as close to the surface as possible without damaging the new growth around it.
Now set the pot in a sunny location and enjoy mint’s tasty leaves all summer long! The plant will fill in quite quickly.
And those two mint plants just weeks later:
I hope you’ve found this look at how to transplant mint helpful and informative!
- Fresh potting soil
- New pot or sanitized old pot
- Soil scoop or hand shovel (optional)
- Pruners or garden scissors
- Select a pot. The new pot should accommodate the root ball, vertically, with an inch or two spare for new soil in the bottom of the pot. There should be 1/2" to 1" of new room around the sides. The pot will need a drainage hole (cover with a piece of screen if large).
- Set the plant in the center, and add more soil all around the sides, up to the surface. Press down on the both the plant and soil to firm everything in place.
- Trim away any dead stems to allow room for new growth. Water thoroughly, and place pot in a sunny location.