Clover, primarily species of the genus Trifolium, is a legume long valued in agriculture for its ability to improve soil health. This flowering plant engages in a symbiotic relationship with Rhizobium bacteria, which allows it to pull atmospheric nitrogen gas from the air and convert it into a usable form within root nodules. Companion planting is the strategic practice of growing different species in close proximity to encourage mutual benefit, such as enhanced nutrient availability, improved pest control, or better soil structure. Harnessing clover’s natural ability to fix nitrogen and serve as a living groundcover is the foundation for successful companion planting.
Clover Varieties and Their Primary Roles
The choice of clover variety is paramount, as their growth habits dictate their best companion pairings. White clover (Trifolium repens) is a low-growing, perennial species that spreads by creeping stems called stolons, making it resilient to foot traffic and frequent mowing. Its primary role is as a permanent underplanting or turf component, providing continuous nitrogen and soil coverage.
Red clover (Trifolium pratense) is a taller plant, typically a biennial or short-lived perennial, with a robust taproot that can reach six inches or more into the soil. This variety is traditionally used for hay production or as a deep-reaching soil builder, as its roots break up compaction and scavenge subsoil nutrients. It is less suitable for a closely mowed lawn environment due to its upright growth habit.
Crimson clover (Trifolium incarnatum) is an annual species known for its rapid, upright growth and vibrant flowers. It is often employed as a quick-acting winter cover crop or green manure, providing a large flush of biomass and nitrogen that can be incorporated into the soil before planting spring vegetables.
Companion Planting for Turf and Groundcover
Integrating clover into a turf or lawn area provides significant ecological and maintenance benefits by creating a more self-sustaining ecosystem. White clover, particularly smaller cultivars known as microclover, is the preferred choice for pairing with perennial grasses like Kentucky bluegrass, fescues, or perennial ryegrass. The low-growing habit of these varieties blends well with the turfgrass, providing a uniform appearance.
The clover’s nitrogen-fixing capability directly feeds the neighboring turfgrass, which is a heavy nitrogen feeder. Studies indicate that a healthy clover-grass mixture can fix between 100 and 200 kilograms of nitrogen per hectare annually. This consistent nitrogen supply helps the lawn maintain a greener color. Furthermore, the dense, spreading growth of white clover effectively shades the soil surface, aiding in weed suppression and competing directly with common lawn weeds.
Companion Planting for Vegetable and Fruit Production
In a vegetable garden or orchard, clover acts as a living mulch, providing numerous benefits. Heavy-feeding vegetables, such as corn, squash, and brassicas like cabbage and broccoli, benefit greatly from interplanting with clover, as their high nitrogen demand is partially met by the legume. For row crops, the clover is often seeded in the pathways between rows, or undersown after the main crop is established to minimize early competition.
Clover’s dense canopy helps to moderate soil temperature and retain moisture by reducing evaporation. A common technique is “chop and drop,” where the clover is periodically mowed or scythed and the clippings are left to decompose around the base of the cash crop. This practice releases the fixed nitrogen and other nutrients directly into the root zone.
In permanent plantings like orchards or berry patches, perennial white clover is ideal for a stable understory. Interplanting clover with crops like cabbage can suppress populations of pests such as the cabbage aphid by interfering with colonization and increasing beneficial ground beetles. Crimson clover is often used in annual systems, providing a large burst of nitrogen before being terminated and incorporated into the soil just before planting, maximizing nutrient release for the succeeding crop.
Plants to Avoid Pairing with Clover
While clover is highly beneficial, its vigorous, competitive nature means it is not a suitable companion for all plants. Plants that thrive in lean, dry, or alkaline soil conditions should be kept away from clover, which prefers moist, nitrogen-rich environments. The constant release of nitrogen and the added moisture retention from the clover can be detrimental to Mediterranean herbs like rosemary or lavender, which rely on low-fertility, well-drained soil.
High competition for water and root space is another significant concern, particularly with perennial white clover. Delicate or newly transplanted seedlings, as well as shallow-rooted cash crops like strawberries, can be easily choked out or suffer reduced yields if the clover is not aggressively managed. The clover’s rapid growth and dense root mat can outcompete the desired plant for resources.