How to Control Catmint Plant

Catmint spreads fast but stays manageable with regular pruning, deadheading, and division every few years. Use physical barriers or containers to stop underground runners. Remove unwanted seedlings early and cut back hard in late fall or early spring to keep plants compact and blooming.

Catmint is one of those plants that gardeners either love or learn to respect fast. It blooms for months, attracts pollinators, smells amazing, and asks for almost nothing in return. But give it an inch, and it will take three feet. Before you know it, that tidy mound has swallowed the path, crowded the roses, and seeded itself into the lawn. If you have ever wondered how to control catmint plant growth without losing your mind or your favorite perennials, you are in the right place.

The good news is that catmint responds well to a few simple habits. You do not need chemicals or complicated techniques. You just need to understand how it grows and then stay a step ahead. This guide walks you through everything from pruning and deadheading to division, barriers, and full removal if it comes to that. Let us dig in.

Key Takeaways

• Prune regularly: Cut back catmint after first bloom to prevent flopping and encourage a second flush of flowers.
• Deadhead spent blooms: Remove faded flowers before they set seed to stop unwanted seedlings from popping up everywhere.
• Divide every 3 to 4 years: Dig up and split clumps in spring or fall to control size and rejuvenate older plants.
• Use barriers or containers: Install edging 12 inches deep or grow in pots to block underground runners from spreading.
• Remove seedlings early: Pull volunteer plants while roots are shallow to prevent them from establishing.
• Cut back hard in late fall: Shear plants to 3 to 4 inches above ground after frost to tidy the garden and reduce spring work.
• Know when to remove completely: If catmint becomes invasive, dig out all roots or smother with cardboard and mulch for a full season.

Quick Answers to Common Questions

When is the best time to divide catmint?

Early spring when new shoots appear or early fall at least 6 weeks before ground freeze. Water deeply the day before dividing.

How do I stop catmint from seeding everywhere?

Deadhead immediately after the first bloom fades. Shear the whole plant to 6 to 8 inches. This removes developing seeds and triggers a second bloom.

What depth of barrier stops catmint rhizomes?

Install edging 12 to 18 inches deep. Rhizomes typically run 4 to 8 inches deep. The top of the barrier should sit 1 inch above soil level.

Can I grow catmint in a container permanently?

Yes. Use a pot at least 16 inches wide and deep. Repot or root-prune every 2 years. Move to an unheated garage in winter or sink the pot in the ground.

How do I remove catmint completely without chemicals?

Dig out the entire root mass 12 to 14 inches deep, removing all rhizome pieces. Or smother with cardboard and 6 inches of mulch for one full growing season.

Understanding How Catmint Grows and Spreads

Catmint, or Nepeta, is a hardy perennial in the mint family. Like its cousins, it spreads two ways. Above ground, it forms a loose mound of aromatic gray-green leaves and lavender-blue flower spikes. Below ground, it sends out rhizomes. Those are horizontal stems that creep just under the soil surface. New shoots pop up from nodes along those rhizomes. That is how a single plant turns into a wide colony over a few seasons.

Catmint also self-seeds. The tiny seeds ripen in late summer and fall. Wind, rain, and passing animals scatter them. Next spring, you find seedlings in gravel paths, between pavers, and in nearby beds. Some varieties seed more aggressively than others. Nepeta faassenii cultivars like ‘Walker’s Low’ and ‘Cat’s Meow’ are sterile or nearly so. They spread mainly by rhizomes. Species types like Nepeta cataria (true catnip) and Nepeta racemosa seed heavily. Knowing which one you have helps you plan the right control strategy.

Clump-Forming vs. Running Types

Not all catmint behaves the same way. Clump-formers stay put and slowly widen from the center. Runners send out long rhizomes that pop up a foot or more from the parent plant. ‘Walker’s Low’ is a clump-former that gets wide but does not run. ‘Six Hills Giant’ runs more. ‘Blue Wonder’ stays compact. If you are buying new plants, read the label or ask the nursery. Choose clump-forming varieties for tight spaces. Save the runners for areas where you want a ground cover effect.

Why Control Matters

Uncontrolled catmint shades out smaller neighbors. It flops open in the center, leaving a bare hole. It seeds into lawns and cracks. It can even jump into natural areas if you live near woods or meadows. Regular control keeps plants dense, floriferous, and well-behaved. It also makes division easier because you are working with younger, healthier roots.

Pruning and Deadheading for Shape and Bloom

Pruning is your first and most frequent tool for controlling catmint. It does three things. It keeps plants compact. It prevents the center from opening up. And it triggers a second or even third bloom cycle. The timing and method depend on what you are trying to achieve.

The Chelsea Chop in Late Spring

In late May or early June, when stems are 12 to 18 inches tall and flower buds are forming, shear the whole plant back by half. Use hedge shears or sharp bypass pruners. Cut just above a set of leaves. This delays flowering by two to three weeks but produces shorter, sturdier stems that do not flop. It also doubles the number of flowering stems because each cut point branches. Do this every year for the neatest habit.

Deadheading After First Bloom

When the first flush fades in early summer, shear the entire plant back to 6 to 8 inches. Remove all spent flower spikes and the top third of foliage. Water well and add a light side-dressing of compost. Within two weeks, fresh growth appears. In three to four weeks, you get a second bloom that often lasts into fall. Deadheading also removes developing seeds. That alone saves hours of weeding later.

Mid-Season Shape-Up

If you missed the first deadheading or the plant gets ragged in July, give it a light trim. Cut back any long, floppy stems to a leaf node. Remove yellowed or damaged leaves. This tidies the mound and improves air flow, which reduces powdery mildew risk. Do not cut back hard after August in cold climates. Late tender growth may not harden off before frost.

Fall Cleanup Cut

After a few hard frosts, usually in November, cut all stems to 3 to 4 inches above the crown. Leave the basal foliage if it looks green and healthy. In warmer zones, you can wait until late winter. This removes overwintering sites for pests and diseases. It also makes spring division easier because you can see the crown clearly.

Dividing Catmint to Control Size and Vigor

Division is the single best way to control catmint plant width and rejuvenate tired clumps. Over time, the center of a clump dies out. The live growth forms a ring around a dead hole. Flowers get smaller. Stems get weaker. Division resets the clock. Aim to divide every three to four years in spring or early fall.

When to Divide

Spring division works well as soon as new shoots appear, usually April in most zones. The plant has all season to recover. Fall division should happen at least six weeks before ground freeze. September is ideal. Water the plant deeply the day before. Cool, cloudy days reduce transplant shock.

Step-by-Step Division

Dig around the clump 6 to 8 inches out from the outer stems. Go down 10 to 12 inches to get most of the root mass. Lift the whole clump. Shake or wash off excess soil so you can see the roots and crown. Use a sharp spade, knife, or two forks back-to-back to split the clump into sections. Each division needs 3 to 5 healthy shoots and a good root bundle. Discard the woody, dead center. Replant divisions at the same depth, 18 to 24 inches apart. Water thoroughly. Mulch with 2 inches of shredded leaves or bark.

What to Do With Extra Divisions

You will almost always have more divisions than space. Pot them up for plant swaps. Donate to community gardens. Give to neighbors. Or compost the extras. Do not dump them in wild areas. Even sterile cultivars can spread vegetatively if rhizome pieces touch moist soil.

Division as a Control Tool

If a clump has jumped its bounds, dig the whole thing. Keep only the youngest, most vigorous outer sections. Replant one division back in the original spot. That instantly reduces the footprint by 75 percent or more. It also gives you a chance to amend the soil and reposition the plant if it was crowding a path or another perennial.

Physical Barriers and Containment Strategies

For running types or plants near lawns and paths, barriers stop rhizomes cold. The key is depth. Catmint rhizomes typically run 4 to 8 inches deep. A barrier must go deeper.

Deep Edging Materials

Use high-density polyethylene (HDPE) edging, 12 to 18 inches tall. Install it in a trench so the top sits 1 inch above soil level. Overlap seams by 6 inches and secure with landscape staples. Metal edging works too but can rust. Recycled plastic lumber boards, 2 by 6 or 2 by 8, sunk vertically make a durable wall. For a cheaper option, sink 12-inch wide strips of heavy pond liner or thick cardboard (triple layer) vertically. Cardboard rots in two to three years, so plan to replace it.

Container Growing

Growing catmint in pots is foolproof containment. Choose a container at least 16 inches wide and deep. Use a gritty, well-draining mix. One part potting soil, one part coarse sand or perlite, one part compost. Water when the top inch dries. Fertilize monthly with diluted liquid fertilizer. In winter, move pots to an unheated garage or sink them in the ground to protect roots. Repot every two years or root-prune by slicing off the outer inch of root ball and refreshing the mix.

Raised Beds with Bottom Barriers

If you build a raised bed for catmint, line the bottom with hardware cloth (1/4 inch mesh) before adding soil. This lets water drain but blocks rhizomes from escaping downward. It also keeps out voles. The bed sides act as above-ground barriers. This is a great solution for formal herb gardens or small yards.

Trenching as a Low-Tech Barrier

Dig a 6-inch wide, 10-inch deep trench around the catmint bed. Leave it open or fill with coarse gravel. Once or twice a year, run a sharp spade down the trench wall to sever any rhizomes trying to cross. This works well in vegetable gardens where you already cultivate between rows.

Managing Self-Seeding and Volunteer Seedlings

Even with barriers, seeds can travel. Managing seedlings is easier than digging out established plants. The trick is early detection and quick action.

Identify Catmint Seedlings

Seedlings have opposite, oval, slightly fuzzy leaves with scalloped edges. They smell minty when crushed. The first true leaves look like miniature adult leaves. They often appear in clusters because seeds fall in groups. Learn to spot them at the cotyledon stage. That is when they are easiest to pull.

Pull When Soil Is Moist

After rain or irrigation, grasp the seedling at the base and pull slowly. The taproot slides out clean. If it breaks, use a narrow trowel or hori-hori knife to get the root. Do not just hoe the tops. Catmint resprouts from root fragments. Drop pulled seedlings in a bucket, not on the bed. They can re-root if left on moist soil.

Mulch to Suppress Germination

A 2 to 3 inch layer of shredded bark, straw, or leaf mold blocks light and reduces seed germination by 80 percent or more. Replenish mulch annually. Keep it a few inches away from crowns to prevent rot. Mulch also makes seedlings easier to pull because roots stay in the loose mulch layer, not the soil.

Deadhead Before Seeds Mature

This is the most effective prevention. As soon as flower spikes turn brown, shear them off. Do not wait for the little nutlets to turn black. One plant can produce hundreds of seeds. A five-minute deadheading session in July saves hours of weeding in April.

Pre-Emergent Options

Corn gluten meal applied in early spring (when forsythia blooms) inhibits seed germination. It is organic and safe for established plants. It does not kill existing seedlings. Apply at 20 pounds per 1,000 square feet. Water lightly after. Note that it also stops desirable self-sowers like poppies and larkspur. Use selectively.

Removing Catmint Completely When Necessary

Sometimes a plant is just in the wrong place. Or it has become a monoculture. Or you are redesigning the bed. Full removal takes persistence but it is doable without herbicides.

Digging Out the Whole Plant

Water deeply the day before. Cut top growth to 6 inches. Dig a trench 12 inches out from the outermost stems. Go down 14 to 16 inches. Undercut the root ball. Lift the whole mass. Shake off soil. Pick through the hole and remove every white rhizome piece you see. Even a 1-inch segment can regrow. Sift the soil through a 1/4 inch screen if the infestation was heavy. Refill with clean soil or compost.

Smothering with Cardboard and Mulch

For large patches or if digging is impractical, smothering works. Cut all growth to ground level. Cover the area with overlapping cardboard (remove tape and staples). Wet it thoroughly. Top with 6 inches of wood chips, straw, or leaves. Leave for one full growing season. The lack of light starves the roots. Check occasionally and pull any shoots that appear at the edges. After a year, the cardboard rots. You can plant directly into the mulch.

Solarization in Hot Climates

In zones 7 and up, clear plastic solarization kills roots and seeds in 4 to 6 weeks during peak summer. Mow the catmint low. Water deeply. Cover with 1.5 to 2 mil clear UV-resistant plastic. Bury the edges in soil to seal. The trapped heat reaches 120 to 140 degrees Fahrenheit. This kills rhizomes down to 12 inches. Remove plastic in fall. Plant a cover crop or mulch heavily.

Follow-Up Monitoring

No method is 100 percent perfect on the first try. Check the area monthly for the first year. Pull any resprouts immediately. They will be weak and easy to remove. After two seasons with no regrowth, you can consider it gone.

Seasonal Care Calendar for Controlled Catmint

Putting it all together, here is a simple year-round schedule. Adjust months for your climate.

Early Spring (March to April)

• Cut back dead stems to 3 to 4 inches.
• Apply 1 inch compost around crowns.
• Divide clumps older than 3 years.
• Install or check barriers.
• Apply corn gluten if using pre-emergent.

Late Spring (May to June)

• Perform Chelsea Chop when stems reach 12 to 18 inches.
• Scout for seedlings weekly. Pull on sight.
• Mulch beds if not done in fall.

Early Summer (June to July)

• Deadhead first bloom flush. Shear to 6 to 8 inches.
• Water deeply after shearing.
• Side-dress with compost or light fertilizer.
• Sever rhizomes at trench barriers.

Mid to Late Summer (August)

• Light trim only if needed for shape.
• Continue seedling patrol.
• Stop fertilizing after mid-August.

Fall (September to November)

• Divide in early fall if missed in spring.
• Plant new divisions.
• After frost, cut back to basal foliage.
• Refresh mulch to 2 to 3 inches.

Winter (December to February)

• In cold zones, leave stems for crown protection.
• In warm zones, cut back in late winter.
• Plan next year’s barrier repairs or bed edits.

Common Mistakes That Make Control Harder

Even experienced gardeners slip up. Here are the top pitfalls and how to avoid them.

Letting the First Bloom Go to Seed

It is tempting to enjoy every flower. But those seeds are next year’s weeds. Deadhead religiously. Set a calendar reminder for late June.

Planting Too Close to Lawns or Paths

Give catmint at least 18 inches of bed space from edges. Rhizomes will cross a 6-inch gap in one season. Use a barrier if the bed is narrow.

Skipping Division

A 5-year-old clump is a nightmare to divide. The center is concrete-hard. Roots are a tangled mat. Divide on schedule. Your back will thank you.

Using Weed Fabric Under Mulch

Weed fabric traps rhizomes on top. They root into the fabric. Removal becomes a horror show. Use organic mulch directly on soil. It feeds the soil and lets you pull seedlings easily.

Composting Seed Heads or Rhizomes

Home compost piles rarely get hot enough to kill catmint seeds or rhizome fragments. Bag and trash them. Or burn if local laws allow. Municipal yard waste facilities usually reach killing temperatures.

Choosing the Right Catmint for Your Space

Prevention starts at the nursery. Pick a variety that matches your maintenance willingness.

Low-Spread, Low-Seed Varieties

• ‘Walker’s Low’: Clump-former, sterile, 24 to 30 inches tall. Perennial Plant of the Year 2007.
• ‘Cat’s Meow’: Compact, 18 to 20 inches, sterile, dense habit.
• ‘Purrsian Blue’: Tight mound, 14 to 18 inches, very little seeding.
• ‘Junior Walker’: Dwarf ‘Walker’s Low’, 15 to 18 inches.

Moderate Spreaders (Good for Massing)

• ‘Six Hills Giant’: 30 to 36 inches, runs slowly, some seeding.
• ‘Blue Wonder’: 12 to 15 inches, spreads steadily, light seeding.
• ‘Dropmore’: 18 to 24 inches, hybrid vigor, moderate seeding.

Aggressive Types (Use With Caution)

• Nepeta cataria (Catnip): Seeds prolifically, runs, 3 to 4 feet tall.
• Nepeta racemosa species: Seeds heavily, runs, 12 to 18 inches.
• Nepeta x faassenii ‘Select Blue’: Runs more than named cultivars.

Container-Only Candidates

If you love catnip for tea or cats, grow it in a pot. Sink the pot in the bed if you want the look. The pot contains roots and seeds. Repot annually.

Dealing with Catmint in Mixed Borders

Catmint plays well with others if managed. Its loose habit hides the bare legs of roses. Its bloom time bridges spring bulbs and summer perennials. But it bullies slow growers.

Good Companions

• Roses (hides thorny canes, same sun and water needs)
• Salvia (similar habit, sequential bloom)
• Yarrow (tough, same conditions)
• Ornamental grasses (contrast texture)
• Coneflowers (sturdy, deep roots)
• Russian sage (airy, late bloom)

Plants to Protect

• Small alpines and rock garden plants
• Newly planted perennials
• Spring ephemerals (catmint shades them out)
• Shallow-rooted bulbs like crocus

Planting Strategy

Plant catmint in drifts of 3, 5, or 7. Space 18 to 24 inches apart. Put aggressive neighbors like coneflowers or grasses on the outside of the drift. They hold the line. Put delicate plants on the inner side or in front where catmint gets cut back. Use the Chelsea Chop on the front row only. That creates a tiered effect and keeps the back row taller for depth.

Tools That Make Control Easier

You do not need fancy gear. A few good tools save hours.

Essential Tools

• Bypass pruners: Felco or ARS for clean cuts on live stems.
• Hedge shears: 8 to 10 inch for shearing whole plants fast.
• Hori-hori knife: Japanese soil knife for digging seedlings and dividing.
• Garden fork: Flat-tined for lifting clumps without slicing roots.
• Sharp spade: For cutting rhizomes at barriers and digging out plants.
• Narrow trowel: For tight spots between perennials.
• Kneeling pad or bench: Your knees will thank you.

Nice-to-Have Tools

• Soil sieve: 1/4 inch mesh for sifting rhizomes from soil.
• Reciprocating saw with pruning blade: For dividing massive old clumps.
• Battery hedge trimmer: If you have 20+ plants.
• Weed torch: For cooking seedlings in gravel paths (use caution).

Frequently Asked Questions About Catmint Control

Here are answers to the questions gardeners ask most.

Does catmint spread by runners or seeds?

Both. Rhizomes spread the clump outward. Seeds start new plants at a distance. Sterile cultivars like ‘Walker’s Low’ only run. Species types do both heavily.

How deep do catmint roots go?

Most roots are in the top 8 to 10 inches. Rhizomes run 4 to 8 inches deep. Taproots on older plants can reach 14 inches. Dig 12 to 14 inches for complete removal.

Can I mow catmint to control it?

Mowing prevents seeding and weakens plants over time. But it also destroys the ornamental value. Use a string trimmer or shears for selective control. Mow only if you are converting a patch to lawn.

Is catmint invasive?

In most of North America, cultivated catmint (Nepeta x faassenii) is not legally invasive. It is aggressive in gardens. True catnip (Nepeta cataria) is listed as invasive in some western states. Check your state’s list.

Will vinegar kill catmint?

Horticultural vinegar (20% acetic acid) burns top growth. It does not kill established roots. Repeated applications may weaken a plant enough to dig it out. It also kills everything else it touches. Not recommended for garden beds.

Can I plant catmint near my vegetable garden?

Yes, with a barrier. Catmint attracts beneficial insects. But it will invade raised beds if rhizomes cross. Install 12-inch deep edging between the herb bed and vegetables.

How do I stop catmint from flopping open?

Chelsea Chop in late spring. Deadhead after first bloom. Give full sun (6+ hours). Avoid rich soil and excess nitrogen. Stake early with grow-through supports if needed.

What is the difference between catmint and catnip?

Catnip is Nepeta cataria. It is weedy, tall, and cats go crazy for it. Catmint usually refers to ornamental hybrids like Nepeta x faassenii. They are lower, showier, and less attractive to cats. Both are Nepeta.

Conclusion

Controlling catmint is not a battle. It is a conversation. You listen to the plant. It tells you when it needs a haircut, when it is crowded, when it is seeding. You respond with shears, a spade, a barrier. Ten minutes here. Twenty there. The reward is a plant that blooms for months, feeds bees, smells like heaven, and stays exactly where you put it. Start with one habit this season. Deadhead after the first bloom. Or divide that old clump. Or install edging along the path. Small steps. Consistent steps. That is how to control catmint plant growth for good. Your garden will thank you. And so will your back.

Frequently Asked Questions

How often should I prune catmint to keep it controlled?

Prune three times per year for best control. Do the Chelsea Chop in late spring, deadhead after first bloom in early summer, and cut back to 3 to 4 inches after frost in late fall. Light shaping in midsummer is optional.

Will catmint choke out other perennials?

Yes, catmint can overwhelm smaller or slower-growing neighbors. Its dense foliage shades out low plants. Give it 18 to 24 inches of space and divide every 3 to 4 years. Use barriers near delicate plants.

What is the Chelsea Chop and does it work on catmint?

The Chelsea Chop is shearing plants back by half in late spring when stems are 12 to 18 inches tall. It works excellently on catmint, producing shorter, sturdier stems, more flowers, and a neater mound that does not flopen open.

Are there catmint varieties that do not spread aggressively?

Yes. ‘Walker’s Low’, ‘Cat’s Meow’, ‘Purrsian Blue’, and ‘Junior Walker’ are clump-forming, sterile or low-seed cultivars. They spread slowly by rhizomes only and stay in a tidy mound for years.

Can I compost catmint trimmings and roots?

Compost leafy trimmings freely. Do not compost seed heads or rhizome pieces. Home piles rarely get hot enough to kill them. Bag and dispose of reproductive parts in trash or municipal yard waste.

Why does my catmint have a dead center?

This is natural aging. The oldest roots in the center die out while new growth rings the perimeter. It signals the plant needs division. Dig, discard the dead center, and replant the vigorous outer sections.