Catmint (Nepeta) is a favored perennial among gardeners, valued for its fragrant foliage, long blooming period, and general resilience. Although this plant is famously tough, a common complaint is that it often loses its upright structure and becomes “floppy.” This sprawling habit makes the plant look unkempt and less attractive. Understanding the factors that lead to this loss of structure is the first step toward maintaining a dense, tidy plant.
Diagnosing Hydration and Heat Stress
Floppiness is often a temporary symptom related to the plant’s immediate environment, specifically its water status and exposure to extreme temperatures. Catmint is highly drought-tolerant once established, but it requires water, especially during its first year or in periods of intense heat. An underwatered plant displays limp leaves and a generalized droop as its cells lose turgor pressure, but this wilting usually resolves quickly after a thorough watering session.
Conversely, the same floppy appearance can indicate overwatering or insufficient drainage. When roots sit in saturated soil, they become oxygen-deprived, which impairs their ability to draw up water and nutrients, leading to a wilt that mimics drought stress. High summer temperatures and intense midday sun can also cause temporary wilting even if the soil moisture is adequate. The plant wilts as a self-protective mechanism to minimize water loss through transpiration.
Structural Instability Caused by Soil Richness
A chronic cause of catmint floppiness relates directly to the quality of the soil and the nutrients it contains. Catmint species, particularly popular hybrids like Nepeta x faassenii, naturally thrive in lean, well-drained, or poor soils. When planted in overly rich garden beds or fertilized frequently, the plant is encouraged to grow too rapidly.
Excessive nitrogen promotes lush, rapid vegetative growth, resulting in stems that are tall but structurally weak. These “leggy” stems cannot support the weight of the leaves and flowers, causing the entire plant to splay open, particularly after heavy rain or wind. To prevent this structural weakness, avoid planting catmint near heavy-feeding plants that require high-nitrogen fertilizers. Amending the soil with sand or grit to improve drainage and reduce nutrient density can discourage the excessive, weak growth.
Restoring Shape Through Pruning and Variety Selection
Pruning Techniques
Once catmint reaches its full height and begins to flower, the weight of the spent blooms can cause it to flop outwards, leaving a hole in the center. Shearing or deadheading is effective at resetting the plant’s structure and encouraging a second, more compact flush of growth. After the first major flush of flowers fades, cutting the entire plant back by one-third to one-half of its height will stimulate new stems that are shorter and denser.
Another technique to create a sturdier structure is the “Chelsea Chop.” This involves cutting back the plant’s stems by about one-third in late spring or early summer. This preemptive cut delays the initial bloom but forces the plant to branch out lower down on the stem. The resulting growth is more compact, creating a bushier plant less likely to flop when heavy with flowers.
Selecting Compact Cultivars
Selecting the right cultivar can prevent floppiness entirely. Taller varieties, such as ‘Walker’s Low’ (named for a garden and not its height), are inherently more prone to splaying. Newer, more compact cultivars have been specifically bred for a naturally dense habit. Choosing shorter varieties like ‘Cat’s Meow’ (16 to 18 inches) or ‘Purrsian Blue’ (10 to 15 inches) results in a naturally self-supporting plant that maintains its neat shape without aggressive pruning or staking.