The mint family encompasses some of the home garden’s most vigorous herbs (and weeds!). Many experienced gardeners have fallen victim to a particularly aggressive patch of mint taking over an entire bed seemingly overnight. Yet, with its rich aroma and nearly unkillable nature, no one wants to exclude this plant from their herb garden.
Culinary mint (Mentha spp.) is a small but mighty perennial that can thrive in various climates. It’s great in several dishes and drinks and is commonly planted to repel pests. Spearmint, or Mentha spicata, is the most popular variety.
In this article, I’ll teach you about mint growth stages and offer tips for successfully growing this herb yourself.
- Conditions for Growing Mint in the Garden
- Mint Growth Rate
- Growth Stages of Mint
- When to Harvest Mint
- Mint Growth Stages FAQs
Conditions for Growing Mint in the Garden
Mint is a herbaceous perennial. Though the stems and leaves die back to the ground in inclement weather (either too hot or too cold), mint will regrow when things return to normal.
A single mint plant can live for five years or longer with proper care. According to Utah State University, mint is typically hardy down to -20°F.
You can grow mint in the garden, in raised beds, in outdoor containers, and even in a small pot perched on your kitchen windowsill. For reasons we’ll touch on throughout this article, however, I usually don’t recommend planting mint in a normal in-ground garden bed!
Mint tolerates full or partial sun. Like most plants, it likes rich soil with plenty of moisture but can succumb to root rot if waterlogged. For the most vigorous, flavorful mint possible, fertilize every month to 2 months to supplement the existing soil.
Mint Growth Rate
Young mints can grow an inch or more per week, and you can begin harvesting in just 60 days. Once established, plants can easily spread at the same rate. Unsurprisingly, mint can quickly overtake a garden if not well-monitored!
Remember that growth will naturally ebb and flow depending on the environment, time of year, and other factors affecting your mint plant’s health. Focus on quality rather than quantity for the most flavorful mint harvest possible.
Growth Stages of Mint
The mint life cycle is relatively straightforward. Still, there’s much to learn about this tough little herb, including how it can completely take over a garden plot if not well-managed!
1. Seed Germination
Mint is commonly grown from seed. The small seeds can be found at nearly any garden supply store and will germinate in the spring when temperatures hover around 70°F. You can expect to see signs of germination within just 7 to 14 days.
Mint and its close relatives are classified as dicots in the plant world. Among other things, this label indicates that mint plants start life with two embryonic leaves called cotyledons.
All flowering plants possess cotyledons. However, the number and location can vary. Cotyledons are the plant’s first leaves, developing in the seed before sprouting.
In the case of mint seedlings, the cotyledons are typically the first plant structure to break through the soil. The mint plant uses energy stored in the cotyledons to sprout and produce its first ‘true’ leaves.
Note that cotyledons are very simple in appearance, and it can be hard to tell a mint seedling apart from any other vegetable or herb at this stage. I highly recommend using labels if you plan to start a load of seeds indoors!
3. Vegetative Growth
The mint seedling should develop true leaves within 14 to 20 days. These leaves will have a more distinct appearance than the cotyledons and will take over photosynthesis from this point forward. (It’s also common for the cotyledons to fade away at this stage.)
New leaves will continue to emerge from the tip of the main stem. Mint plants have distinctly square stems. Leaves have slightly serrated margins and appear on the stem in neat pairs.
4. Root Growth
We know that mint spreads from the point it was first planted, but how does it go about it? It uses its roots!
Mint plants have specially modified stems called rhizomes. These stems are unique in a few ways: a) rhizomes grow underground as part of the root system, b) rhizomes grow horizontally rather than up, and c) rhizomes possess buds that can sprout new tissue.
When you plant mint in the ground, it sends out rhizomes to explore the surrounding soil. As long as nothing is in the way, each rhizome will find a cosy spot and produce its roots and shoots. That ‘new’ mint plant will then repeat the process. And so on.
This is why I always recommend planting mint in some type of container. If you don’t corral your mint plants from the start, they can quickly take over far more garden space than you had planned. Mint’s vigorous, adaptable nature also means it can compete with other nearby plants, choking them out as it spreads.
Mint plants most often flower during the summer months. Like some other garden herbs, mint will flower in response to stress caused by high daytime temperatures or mild drought.
Mint flowers form spike-shaped clusters. The flowers themselves range from white to pink or purple.
While flowering is a natural part of the mint life cycle, few gardeners are excited to see the blooms on their plants. Flowering can cause a mint plant to go leggy and impede the flavor of the leaves.
The one time you’ll want to encourage flowering is if you’re planning to collect and save mint seeds for future planting.
Mint plants require cross-pollination to produce seeds. However, numerous species of bees and other pollinating insects adore mint pollen and nectar, so gardeners rarely need to worry about cross-pollination.
Keep in mind that different mint varieties can easily cross-pollinate. The result of these crosses can be unpredictable. If you want to save specific seeds from your garden, carefully plant different kinds of mint in the same area.
7. Seed Development
After successful pollination, mint flowers will fade to make room for the seed pods. Wait for the seed pods to dry before collecting seeds for storage. You can place the cut seed heads in a bag and gently shake them to release the seeds from their husks.
Life Cycle of Peppermint
Peppermint (Mentha x piperita) is a super popular hybrid variety of mint. According to the University of Wisconsin, its life cycle differs from other mint species, mostly because the plant doesn’t produce viable seeds.
The only way to propagate peppermint is by dividing an existing plant. This is easy to do since peppermint spreads via rhizomes just like any other type of mint.
A peppermint plant will flower and produce seeds if left to mature. Keep in mind, however, that these seeds are sterile. No amount of time will cause the seeds of a peppermint plant to sprout!
When to Harvest Mint
The leaves of a mint plant are typically harvested for culinary purposes but can also be left to grow as a companion plant for brassicas, carrots, radishes, beets and lettuce. You can also use bundles of mint leaves to repel insects or freshen up a living space.
As a rule, the best time to harvest mint is about halfway through the growing season. This should be shortly before the plant flowers. At this time, the leaves tend to be the most fragrant and flavorful.
If you have a use for a lot of mint at once, I recommend waiting until the plant is just about to flower (as described in the previous paragraph). You can then cut the entire plant to just a few inches tall. If the weather stays consistent, you might get a second harvest from the remaining stem.
If you’re in a rush, mint can technically be picked starting as soon as the plant reaches 4 inches tall. But waiting until the plant is at least 6 inches tall with multiple stems is better.
To harvest mint, use clean kitchen or garden shears or your fingernails to pinch leaves from the stem. Routinely harvesting mint during the season will promote bushier growth.
Mint Growth Stages FAQs
Should I let mint flower?
Mint plants typically flower in the summertime during hot, dry growing conditions. Many gardeners pinch off the developing flowers, as blooming tends to mess with the flavor of harvested mint leaves. However, mint must flower if you want to collect seeds from it.
What are the drawbacks of planting mint?
Gardeners beware! Mint is an aggressive herb that spreads by underground stems and can take over large sections of the garden if left unchecked. It can act as a weed in some areas. I always recommend planting mint in containers to prevent this.
Ben's horticultural interest grew when graduating from Hertfordshire University in 1997. Having contributed to numerous publications including Better Homes & Gardens, Garden Design Magazine, and The English Garden. He is also the author of Propagating Houseplants Made Easy.