How to Plant, Grow, and Care for Pycnanthemum tenuifolium

Pycnanthemum tenuifolium, or narrowleaf mountain mint, is a hardy and adaptable plant that you can plant in your herb garden, along your garden borders, in a rain garden, and between rocks, or as a xeriscaping plant. All parts of this plant, when crushed, have a fragrance of mint.

The dried leaves of this fragrant herbaceous perennial plant emit a mint-like aroma and can be used as a food item. You can boil them to make mint tea! These lovely native plants hail from the rocky woods and open wet thickets of central and eastern North America. Their showy white flowers attract pollinators of all kinds: butterflies, honey bees, wasps, flies, beetles, and moths.

So let’s discuss this lovely plant, and how to grow it in your garden!

What is Pycnanthemum tenuifolium?

The slender mountain mint is part of the mountain mint plant family (Lamiaceae). Also known as narrow-leaf mountain mint, Pycnanthemum tenuifolium features extremely narrow, slender leaves that separate it from other mountain mint species, all of which are native to North America.

Native Area

This herbaceous perennial plant is native to every county of central and southern Illinois and most of eastern North America. It grows in open wet thickets, rocky woods, woodland openings, moist thickets and meadows, limestone glades, acid gravel seeps, and abandoned fields. It’s perfect for native plants and any rain garden in that range.

Characteristics

Pycnanthemum tenuifolium is an erect and tall herbaceous perennial that blooms clusters of tiny, white flowers, and has narrow, needle-like silvery foliage and slender, hairless stems. These plants frequently branch into a shrub-like or bushy formation.

Narrowleaf mountain mint spreads through the ground via rhizomes, allowing it to appear as a striking mass of white flowers in late summer. These plants are a favorite among animals and insects – native bees love to swarm the mildly minty, fragrant white flowers.

Planting

This herb thrives in various soil types and conditions, making it an excellent choice for gardens and natural landscapes. When planting, choose a sunny location with well-drained soil, although it can tolerate partial shade.

Before planting, prepare the soil by loosening it and adding organic matter, such as compost, to enhance drainage and fertility. Space the plants about 12 to 18 inches apart to allow for their natural spread, as they can form dense colonies over time.

After planting, it requires minimal maintenance. Regular watering during dry spells will help establish the plants, but once they are rooted, they are drought-tolerant. Also, prune back to encourage bushier plants.

Care

Now that we’ve discussed this wonderful plant let’s discuss its care and cultivation for that lovely mint-like aroma. You may find your mountain mint is the happiest plant in your garden.

Light

This herb needs full sun but can also survive in partially shaded areas. Heat is no issue for this plant, as it grows wild in areas of the south that are very hot in summer. However, in full sun, give it some afternoon shade. In its hardiness range, the plant is an herbaceous perennial. Leaves die back in winter, leaving lovely seeding flower heads, and return lush and green the following spring from their roots.

Water

This plant needs a low to medium amount of water. Let the soil dry out completely between watering rounds, or water it with drip irrigation or soaker hoses. If you’re setting up an automatic irrigation system, don’t worry about watering mountain mint much after it’s established.

It has some tolerance to drought but may need regular water once per week in the dead heat of summer, especially in full sun. Don’t worry about watering in rainier or temperate times. Varying humidity percentages are appropriate for growing this plant. If you live in a dry area, consider planting your mountain mint in a rain garden to give it the water it needs.

Soil

This mint family plant prefers moist to slightly dry conditions and well-draining soil. Many different types are suitable as long as they retain some water and nutrients but drain well. This plant often grows in rich, loamy, and slightly rocky soil. Open wet thickets, meadows, and bogs are where you find the plants in the wild. Consider these conditions when you’re building soil for your plant. A soil pH of 6.8 is optimal, too.

Temperature

USDA Plant Hardiness Zones 4 to 8 are ideal for this plant, as it is native to rocky woods within these zones. However, with proper care, you can stretch it outside these zones.

As long as your plant is established in an area or container and isn’t exposed to consistent temperatures below 15°F (-9°C), you’re good!

Fertilizing

Pycnanthemum tenuifolium has no special fertilizing needs, it’ll grow without additional fertility. In fact, you might find your plant doesn’t perform as well when supplemental nutrients are added, especially in its native range. A light dressing of compost annually is enough to keep it happy.

Propagation

Propagate your plant via divisions and seeds. For division, cut off the tips of your plant in June, divide a clump of your plant in late fall or early spring, and use stainless steel pruning shears to divide the shallow root system.

For propagation via seeds, collect the seeds after the first few frosts. If the seeds are ripe, they will fall out when you bend over the stem and shake it. Store these in a sealed, refrigerated container and plant them in seed-starting trays six to eight weeks before the last frost. Simply tamp them into the surface of the soil. Harden them off and plant them in your preferred area or container outdoors when spring has arrived.

Maintenance

Pycnanthemum tenuifolium features extremely narrow leaves that may or may not need pruning. To keep your plant from spreading throughout your garden, you can occasionally divide it from the roots and either transplant it into a new area or toss it into your compost pile. You can also control its spread by deadheading spent flowers.

Remove dead and diseased leaves as needed. There’s no need to prune otherwise. Leave the flowers and stalks through the cold months for overwintering native insects and pollinators.

Common Problems

Pycnanthemum tenuifolium, is a low maintenance plant. However, it can face some growing problems.

Growing Problems

Make sure that you don’t overwater your plant or keep it away from sunlight. Your plant needs full sun and dry to lightly moist soil to thrive. If you do this or plant it in compacted soil, you may find fungal rusts are more likely to develop.

Another issue that can arise is when your mint is planted in an area and doesn’t receive enough moisture. In this case, you’ll notice the bottom leaves yellowing and falling off. Increase water frequency in this case.

Pests & Diseases

This plant is virtually pest-free, and is highly deer-resistant and rabbit-resistant. However it can succumb to rust in situations where the fungus that causes the disease is present, and when the plant is placed in conditions it is not suited to growing in. If you notice rust-colored spots appearing on the undersides of leaves in spring, you’re dealing with rust.

There is no cure for rust. Simply remove damaged foliage as it crops up, and ensure your plant is in correct light and soil conditions. Prune the plant to increase air circulation as needed. Also never water the foliage of the plant and only apply irrigation at its base. Plants that are overtaken by rust should be removed and disposed of, but most of the time it doesn’t come to that.

Frequently Asked Questions