Question: I want to add mint to my garden, but I know from previous experience that it can be invasive. What precautions should I take?
Answer: Mint is a low-maintenance, fast-growing perennial herb that grows extremely well in Oregon.
Mint spreads primarily by underground rhizomes or runners that can quickly take over a bed or border. Mint will continue to grow for many years once established.
However, the roots can escape out of the bottom drainage hole. The best way to prevent that from happening is to place the containers on stone slabs throughout the garden. If the roots begin to grow out of the drainage holes, you can easily see them and prune thembefore they take root.
Some gardeners use fabric planter bags that are porous enough to allow the soil to properly drain and allow for good air exchange in the root zone. Because of this, the fabric planter bags do not have drainage holes in them from which roots can escape.
Simply plant the fabric planter bag into the ground leaving the top 3 inches of the bag’s upper rim sticking above the soil’s surface. Mint has long branches that grow upward. These branches eventually grow and flop over, sprawling out on the ground. If you bury the bag completely, the mint roots will spread out over the top of the planter bag and into the garden.
Fill the bag with a 50/50 combination of potting soil and quality compost and then plant your mint. You’ll have to check on the plants every few weeks throughout the growing season and prune the runners that are growing past the boundary of the bag.
Mint can also be controlled by planting it in spaces with impermeable boundaries. A boundary can be created by sinking wood, plastic or metal edging at least 6 inches into the ground to prevent the spread of roots.
There are more than 600 varieties of mint, but two common varieties include spearmint Mentha spicata and peppermint Mentha X piperita. You may want to try other varieties of mint that have interesting flavors and aromas.
If you plant different varieties of mint, plant as far apart as possible. Why? True mint varieties are known to cross pollinate with other types of mint when planted within close proximity. This can result in characteristics from different mint types to appear in one plant, leading to the loss of the plant’s integrity with unfavorable scents or flavors.
Mint grows equally well inside your home or outside in the yard. For growing outside, plant one or two purchased plants about 2 feet apart in moist soil. Or if you prefer, propagate mint by taking cuttings. Take a 6 inch cutting of rooted stems and plant them horizontally in the soil. Mint stems will also root in a glass of water.
Mint prefers a moist but well-drained soil. Most will tolerate some shade, and the variegated types may require some protection from direct sun. Mint should grow to be 1 or 2 feet tall. Remove any unwanted runners and pinch the tips of the plants back regularly.
Mint will bloom from June to September. Right before flowering, cut the stems 1 inch from the ground. You can harvest one mint plant two or three times in one growing season. You can also just pick the leaves as you need them. If you decide to let the mint plants bloom, the small, white flowers will attract bees and butterflies.
Mint is slightly frost tolerant. The top of mint will die back in the winter, but the roots are quite hardy. Lift and replant your mint every three to four years to keep your mint flavor strong. It you don’t replant, mint will weaken and become spindly.
The most common pests of mint plants are aphids and spider mites. These bugs live on the underside of the leaves and cause brown spotting on the plant. They suck the sap out of the leaves which drains the plant of its nutrients. The leaves will turn yellow and eventually fall off.
Knock off any insects using a strong jet of water from a garden hose, being sure to spray the undersides of leaves where pests like to hide.
Mint is a wonderful addition to any garden, but yes, you will need to keep it contained so it doesn’t take over. With a little planning, this is easy to accomplish.