What's Catmint? How to Shear It for a Second Bloom

No, though they are close relatives and the confusion is fair. True catnip is Nepeta cataria, while the plant sold for borders is almost always a Nepeta x faassenii hybrid.

What you are buying is essentially a small aromatic shrub that behaves like one. Catmint builds a dense gray-green mound of small scalloped leaves, covers itself in slender blue-violet spikes for months, and holds that shape through heat and wind that would flatten a softer perennial.

It also stays where you put it, forming clumps rather than running underground, so nothing about its mint-family membership means it will take over a bed.

On a nursery bench the two are easy to separate once you know what to look at. Catnip is coarse and upright with large soft toothed leaves and dull whitish flowers, and next to a garden catmint in full blue it looks like the weed it half is.

Choose on mature spread rather than on flower color, because sprawl is what people regret. A one-gallon pot gives no hint that the plant in it will cover a yard of ground by August.

The named selections split fairly cleanly into two groups.

Compact types hold near 12 to 18 inches and stay tight enough to edge a path without spilling across it. The big billowy ones like 'Six Hills Giant' run 2 to 3 ft and want mid-border company that can hide a base which loosens after the first flush.

Color is the easy part once space is settled. The standard lavender-blue now has deeper violet and even soft pink alternatives, though the blues still read best at a distance and still pull the most bees.

Rich ground grows soft stems, and soft stems cannot hold a mound up once it carries the weight of flowers.

This is a dry-hillside plant by ancestry, so a bed improved for roses gives it more water and more nitrogen than its structure was built for. The result is fast lush growth that splits open at the center by midsummer and a crown that sits wet through winter.

Sun is the other half of the same story. Six to eight hours keeps growth short and firm, and light reaching the plant from more than one side, as along a path or a drive, is what stops it leaning toward the brightest gap.

Water it like the dry-border plant it is, which after the first year means a deep soak every ten to fourteen days and nothing in between.

Let the top 2 inches dry, then water hard enough to reach 6 to 8 inches down so the roots keep chasing moisture downward.

After the first heavy flush a Catmint goes over all at once, splitting at the center and dropping its stems flat across whatever is beside it. Picking off spent spikes one by one will not close that gap, because the stems themselves have finished.

The fix is a haircut, taken with hedge shears and taken across the whole plant at roughly half its height. Do it as soon as the first flush fades rather than waiting to see whether it recovers on its own.

It will look drastic, and that is the point.

Timidity is what makes this job fail, since a light trim leaves the collapsed stems in place and the plant stays shabby. Cut into firm growth and fresh basal foliage pushes within a week or two, followed by a second flush of flower that carries the plant into fall.

A late-season plant can simply be left alone once that second flush fades. In cold zones the top growth dies back anyway, and stems left standing give the crown a little extra shelter through winter.

A clump asks to be divided by going woody and bare in the middle while the outer ring carries on flowering.

Early spring in cold zones is the cleanest window, while warmer gardens can also work in early fall. Either way, do the job in the cool of the morning and keep a bucket of water beside you so the pieces never sit dry in the sun.

Winter looks completely different depending on where you garden, which catches people out. In Zone 3 and Zone 4 the plant vanishes to nothing above ground and comes back later than the spring bulbs around it, so an empty patch in April is not a dead plant.

Some cats ignore garden catmint entirely and some roll in it until it is flat. The hybrids carry less of the compound that drives the response than true catnip does, but that is a weaker reaction rather than a reliable absence of one.

A rolling cat flattens the stems, and eating the plant can matter too. ASPCA lists catnip, Nepeta cataria, as toxic to cats, with vomiting and diarrhea, and no record covers garden Catmint hybrids, so if a cat eats a lot of it, contact a veterinarian or ASPCA Animal Poison Control. What you lose is the shape of a border edge, so put a young plant somewhere a rolling animal will not crush it and give it a season to build a base that can take the traffic.

Insects mostly leave it alone, because the aromatic foliage does the work a spray would otherwise do.

Two get through in stressed conditions. Aphids cluster on soft tips in late spring, especially on plants growing too rich, and spider mites stipple the leaves in a hot dry spell, but neither is usually more than cosmetic on an established mound.