Heather, encompassing true heather (Calluna vulgaris) and heaths (Erica species), is a popular evergreen shrub for ground cover. It does spread, but the rate and nature of expansion depend heavily on the specific variety and environment. Heather is not aggressively invasive and tends to spread slowly, resulting in a dense mat of growth. Understanding the differences in propagation methods is key to managing its presence.
Differentiating Growth Habits
Heather’s spread relates to the lateral growth of a single plant mass rather than the creation of new, distant plants. True Scotch Heather (Calluna vulgaris) varieties typically exhibit a mounding or clumping habit, expanding gradually outward from the center. This expansion is slow, creating a dense, woody dome that can take several years to reach its mature width, often 1 to 2 feet wide.
Conversely, many Erica species (heaths) display more prostrate or creeping forms, making them effective ground covers. Varieties like Winter Heath (Erica carnea) are known for their low-growing, spreading nature, colonizing larger areas more quickly. Gardeners should note whether the cultivar is described as dwarf, mounding, or spreading, as this indicates its mature footprint.
How Heather Spreads Naturally
Beyond the plant’s natural growth habit, heather employs two primary biological mechanisms to create entirely new, separate plants. The most common method in a garden setting is natural layering, particularly among lower-growing Erica varieties. This occurs when a lower stem or branch contacts the soil, encouraging it to spontaneously develop roots. Once rooted, this new section becomes an independent plant, expanding the colony outward from the original mother plant.
The second method is self-seeding, where spent flowers release tiny seeds onto the surrounding soil. Successful germination requires specific conditions, such as disturbed soil, light, and the acidic, well-drained substrate heather prefers, which limits aggressive spread in cultivated beds. While new seedlings can appear, they are generally not numerous enough to be a nuisance and may not reproduce the exact characteristics of the parent plant.
Controlling Growth and Maintenance
Managing the slow spread of heather relies on consistent, annual maintenance. Pruning is the most effective method for controlling the plant’s size and shape, preventing it from becoming woody. For most varieties, this involves shearing back the spent flower spikes and about one-third of the previous year’s growth immediately after flowering.
Pruning should be timed according to the variety: summer-blooming Calluna are pruned in early spring, and winter-blooming Erica are pruned after their bloom cycle finishes. Avoid cutting into old, leafless woody stems, as heather rarely sprouts new growth from old wood, which can leave permanent bare patches. Deadheading spent flowers can reduce self-seeding. For plants that have spread too widely through natural layering, the rooted segments can be severed from the parent plant and transplanted or removed. Physical barriers are seldom necessary, as the spread is slow and easily managed with regular trimming.