Catmint (Nepeta) is a perennial herb favored by gardeners for its aromatic foliage and extended season of delicate, lavender-blue flowers. This hardy plant thrives in tough conditions, often blooming starting in late spring. To keep Catmint looking its best, summer pruning is a beneficial practice that encourages a tidier appearance and a stronger floral display later in the season.
The Necessity of Mid-Season Shearing
Catmint varieties, such as ‘Walker’s Low’ and ‘Six Hills Giant’, produce a vigorous display of flowers during their first major flush in early summer. Once these blooms fade, the stems become elongated and thin, causing the clump to “flop” open in the center. This leggy growth is a natural reaction after the energy expenditure of the initial bloom period. By mid-summer, the plant often appears spent and unkempt.
Shearing addresses the physical appearance and promotes a second, more compact wave of blooms, known as repeat flowering. This process redirects the plant’s energy into new lateral growth rather than seed production. For non-sterile varieties, cutting back also prevents aggressive self-seeding and unwanted spread. A mid-season cut rejuvenates the plant, helping it maintain a dense, mounded habit for the remainder of the growing season.
Step-by-Step Guide to Summer Pruning
The correct time for this mid-season cut is immediately after the peak of the first bloom cycle, typically in late June or early July, before the spent flowers have fully dried out. Tools can include bypass pruners, long-handled shears, or even hedge clippers, depending on the size of the catmint mass. For large plantings, shears make the task quick and efficient.
This process is termed “shearing” because the goal is a uniform cut across the entire plant, not selective deadheading of individual stems. Aim to remove the upper one-third to one-half of the plant’s height, focusing on cutting off all spent flower spikes and the upper, flopping foliage. Leave a base of healthy, green foliage at the bottom of the plant; do not cut the stems back to the ground. Leaving green leaves allows the plant to continue photosynthesis, which fuels new growth and subsequent rebloom. Within two to three weeks, the plant will push out fresh, dense foliage and begin producing new flowers that will last until the first hard frost.
End-of-Season Care for Catmint
Summer shearing is distinct from the final cutback needed for winter dormancy. Once the second flush of blooms finishes and the foliage begins to die back in late fall, the plant is preparing for its rest period. Many gardeners choose to leave the spent foliage standing throughout the winter. This offers insulation to the crown and provides visual interest in the dormant landscape.
If a tidier look is preferred going into winter, the plant can be cut back harder. This should be done only after the plant is fully dormant, typically after several hard frosts. The final cut should remove the old, brown stems down to two to six inches above the ground. Cutting catmint too early in the fall while it is still actively growing can stimulate tender new growth susceptible to freezing damage. Waiting until late winter or very early spring, just before new growth emerges, is often the safest approach for the perennial’s health.