Clover offers many benefits for landscapes, from enhancing soil fertility through nitrogen fixation to serving as ground cover or forage for livestock. Cultivating clover successfully depends on understanding the specific climate, as its ability to thrive is influenced by environmental conditions, particularly temperature extremes.
Understanding Plant Hardiness Zones
Plant hardiness zones guide gardeners and farmers on which perennial plants are most likely to survive winter temperatures in specific geographical areas. These zones are determined by the average annual extreme minimum winter temperature, as defined by the USDA Plant Hardiness Zone Map. Each zone represents a 10-degree Fahrenheit range, divided into ‘a’ and ‘b’ subzones denoting 5-degree Fahrenheit increments. This system helps predict a plant’s winter survival probability for plant selection.
Clover Varieties and Their Hardiness
White Clover
White clover (Trifolium repens) is a low-growing, spreading perennial known for forming dense mats. It remains green throughout the growing season and withstands considerable foot traffic, making it suitable for lawns and pastures. White clover performs well across USDA hardiness zones 3 through 9, demonstrating good cold tolerance and persistence. Its perennial nature allows it to return year after year.
Red Clover
Red clover (Trifolium pratense) is a short-lived perennial or biennial, distinguished by its taller growth habit and larger, more upright stems. It is commonly used for hay, silage, and as a cover crop due to its substantial biomass production and nitrogen-fixing capabilities. Red clover exhibits hardiness across USDA zones 3 to 8, tolerating a broad range of temperatures. Its biennial nature means it typically completes its life cycle within two years.
Crimson Clover
Crimson clover (Trifolium incarnatum) is an annual species known for its striking, elongated crimson-red flower heads and rapid growth. It is primarily used as a winter annual cover crop in warmer regions or as a spring-planted annual in cooler climates. This clover thrives in USDA hardiness zones 6 through 9 when planted in the fall. In colder zones, it is planted in spring and completes its life cycle before the first hard frost.
Other Common Clovers
Alsike clover (Trifolium hybridum) is a short-lived perennial, often found in wetter, cooler climates and tolerates more acidic soils. It is adaptable to USDA zones 3 to 8, showing good cold tolerance. Subterranean clover (Trifolium subterraneum) is an annual species that buries its seed heads, making it useful in grazing systems and reseeding itself. It prefers milder winter climates, performing best in USDA zones 7 to 10.
Optimizing Clover Growth Beyond Zone
While hardiness zones guide temperature suitability, other environmental factors influence clover’s success. Soil pH is important; most clovers prefer a slightly acidic to neutral pH (6.0 to 7.0) for optimal nutrient uptake. Well-drained loamy soils support better growth than heavy clay or overly sandy conditions, and adequate drainage prevents root rot. Light availability is another important factor. Most clover varieties require full sun exposure (at least six hours daily) to achieve full growth and flowering. While some clovers tolerate partial shade, their vigor and density may be reduced. Consistent moisture is also important, particularly during establishment and dry periods, as clovers prefer consistently moist but not waterlogged soil.
Selecting and Establishing Clover
Choosing the right clover variety involves aligning its hardiness zone suitability with your local climate and its intended use. For instance, perennial white clover is often chosen for lawns in zones 3-9 due to its low-growing nature and persistence. Once selected, proper establishment practices are important. Spring or early fall are the most favorable times for planting, allowing plants to establish roots before extreme temperatures. Soil preparation involves light tilling or raking to create a loose seedbed and ensure good seed-to-soil contact. Broadcasting seeds evenly, followed by light raking or rolling, helps secure them. Adequate moisture immediately after planting and during germination is important for seedling emergence.