Ask a master gardener: keep the mint contained in the garden | House and garden

Reply: Mint is a low-maintenance, fast-growing perennial herb that grows extremely well in Oregon.

Mint is spread primarily by underground rhizomes or runners which can quickly invade a bed or border. Mint will continue to grow for many years once established.

However, the roots can escape from the lower drainage hole. The best way to prevent this from happening is to place the containers on stone slabs throughout the garden. If the roots start to grow out of the drainage holes, you can easily see them and prune them before they take root.

Some gardeners use fabric garden bags that are porous enough to allow the soil to drain well and allow good air exchange in the root zone. For this reason, fabric planter bags do not have drainage holes from which roots can escape.

Simply plant the fabric planter bag in the ground, letting the top 3 inches of the top edge of the bag stick out above the soil surface. Mint has long branches that grow upwards. These branches eventually grow and collapse, spreading out onto the ground. If you bury the bag completely, the mint roots will spread 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 will need to check the plants every few weeks throughout the growing season and prune any runners that grow beyond the bag limit.

Mint can also be controlled by planting it in spaces with impermeable boundaries. A boundary can be created by driving edging of wood, plastic or metal at least 6 inches into the soil to prevent root spread.

There are over 600 varieties of mint, but two common varieties are spearmint Mentha spicata and peppermint Mentha X piperita. You might want to try other varieties of mint that have interesting flavors and aromas.

If you are planting different varieties of mint, plant them as far as possible. Why? True varieties of mint are known to cross pollinate with other types of mint when planted nearby. This can lead to the appearance of characteristics of different types of mint in a plant, leading to the loss of the integrity of the plant with unfavorable scents or flavors.

Mint grows just as well inside your home as it does outside in the yard. For growing outdoors, plant one or two purchased plants about 2 feet apart in moist soil. Or if you prefer, propagate the mint by taking cuttings. Take a 6-inch cutting of rooted stems and plant them horizontally in the ground. The mint stems will also root in a glass of water.

Mint prefers moist but well-drained soil. Most will tolerate some shade, and variegated types may require some protection from direct sunlight. The mint should grow to be 1 or 2 feet tall. Remove any unwanted runners and regularly pinch off the tips of the plants.

Mint will bloom from June to September. Just before flowering, cut the stems 1 inch from the ground. You can harvest a mint plant two or three times in a single growing season. You can also just pluck the leaves as you need. If you decide to let the mint plants bloom, the small white flowers will attract bees and butterflies.

Mint is slightly tolerant of frost. The top of the mint will die off in winter, but the roots are quite tough. Lift and replant your mint every three to four years to keep your mint flavor strong. If you don’t replant, the mint will weaken and turn tinny.

The most common pests of mint plants are aphids and spider mites. These insects live on the underside of the leaves and cause brown spots on the plant. They suck the sap from the leaves which drains the plant of its nutrients. The leaves turn yellow and eventually drop.

Kill all insects using a powerful stream of water from a garden hose, making sure to spray the undersides of the leaves where the pests like to hide.

Mint is a wonderful addition to any garden, but yes, you’ll need to contain it so it doesn’t take over. With a little planning, this is easy to achieve.