Ornamental · Fabaceae
Crimson Clover
Trifolium incarnatum
Put it in the ground come fall, and crimson clover repays you with fixed nitrogen and a spring carpet of red.
Full sun
Every 5–10 days
150–210 days
USDA 6–9
Overview
Crimson clover earns its place by what it accomplishes more than by its looks, though it manages both gracefully. Belonging to the pea family, it draws nitrogen from the air and banks it in the roots, the reason gardeners and growers turn to it as a cover crop and green manure. It comes on quickly, holds back weeds, and keeps the bees busy all the while it works.
This is an annual with a brief turn on the stage. Set out in late summer or fall, it settles into a low rosette before the cold, then rises in spring to lift brilliant crimson-red conical flower heads before it seeds and finishes. The pace is the whole appeal: cover and fertility arrive in one season, and then the planting goes under for the crop to come.
Its finest moment is the handoff. Take it down at or just shy of bloom and a wave of nitrogen lands exactly when a hungry successor such as corn is ready for it. Let the season run on and it ripens hard seed, turning up as a volunteer weed in next year's bed.
Care
The short version: give it full sun and well-drained ground, direct-sow inoculated seed about 1/4 inch deep into a firm, moist bed, water it through establishment and then hand the rest to the rain, and bring it down at or before early bloom.
Light
For its fullest growth and bloom, crimson clover asks for full sun, though it will accept partial sun. Set it in deep shade and it turns lean and floppy and fixes less nitrogen, so choose an open, sunlit spot.
Water
Hold the seedbed moist through germination and establishment, then water only when dry spells set in, since a settled stand lives mostly on rain. The one thing it refuses is wet feet, so keep it off soggy or waterlogged ground.
Soil
Give it well-drained loam or sandy loam of moderate fertility. Heavy clay or waterlogged ground holds it back, and it favors a near-neutral pH between 6.0 and 7.0.
Temperature
Built for the cool season, it copes with a broad sweep, from roughly 10°F to 84°F (-12°C to 29°C), while staying less cold-hardy than its clover relatives. Hard freezes in cold zones can thin or finish an overwintering stand.
Humidity
Plain outdoor humidity suits it, so there is no figure to chase. Airflow and drainage carry more weight, since the crown and root rots take hold in cool, wet, crowded settings.
Feeding
Being a nitrogen-fixing legume, it asks for no nitrogen fertilizer; inoculate the seed instead with the right Rhizobium so the plants supply their own. Reach for phosphorus or potassium only when a soil test points to a genuine shortfall.
Pruning
Pruning in the ordinary sense does not apply. The work is termination: mow, till, roll, or let it winterkill at or before early bloom, ahead of hard-seed set, then fold it in as green manure or leave it lying as surface mulch.
Repotting
none
Size & spacing
A stand reaches about 12 to 35 inches (30 to 90 cm) in height, with single plants spreading near 6 to 12 inches (15 to 30 cm). It goes in broadcast or drilled as a thick stand rather than spaced out plant by plant.
When to plant
Crimson clover keeps to the cool season. Get it in the ground from late summer to fall, about 6 to 8 weeks before your first frost, so it builds a crown to carry through winter in mild zones; where it turns cold, sow in early spring instead. Flowers follow the next spring, and you take the stand down at or just before they open.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Not applicable; crimson clover is direct-sown in the field, not started indoors.
- Plant: Sow in late summer to fall, about 6 to 8 weeks before the average first frost, to overwinter in mild zones (roughly USDA 6-9); in colder areas sow in early spring.
- Harvest: Showy brilliant crimson-red elongated conical flower heads appear in spring (about April to May). Terminate at or before early bloom for maximum nitrogen and to prevent reseeding.
Hardiness
USDA hardiness zones: 6–9
Temperature: down to -23°C
Troubleshooting
Nearly every issue with crimson clover comes down to how it was sown or the moment it was terminated. Learn to read the early cues in the planting and at the roots, and a thin patch or a weedy reseed can be settled before it costs you anything. Find your symptom below, then move while there is still time to act.
A patchy, washed-out stand that never fills the bed
When the planting comes up thin and pale, the usual story is that the seed went in without its Rhizobium inoculant, so no root nodules formed and nothing is feeding the stand nitrogen. Add dry ground or loose contact at sowing and the gaps only widen. A few weeks after the seedlings show, lift a couple and look for pink, working nodules at the roots, then refresh the bare spots with fresh inoculated seed pressed into a firm, moist bed.
Fix:
- Use fresh pre-inoculated seed or treat seed with the proper Rhizobium inoculant before sowing
- Sow about 1/4 inch deep into a firm, moist seedbed with good seed-to-soil contact
- Sow 6 to 8 weeks before first frost into adequate moisture, or reseed thin areas
A fall planting that comes up bare in spring
Among the clovers, this one is the least cold-hardy, and a hard winter can thin or empty the planting, particularly in zones colder than about 6. Sow too late and the crowns are simply too young to carry through the cold. Read any winterkilled growth as a free layer of mulch or green manure, and in cold regions plan around it: grow it as a spring-sown annual, or reach for sturdier types such as AU Robin or AU Sunrise.
Fix:
- Treat winterkilled residue as mulch or green manure and follow with a spring crop
- In cold areas grow it as a spring-sown annual instead of overwintering it
- Choose hardier improved types such as AU Robin or AU Sunrise
An uninvited guest in next season's bed
Allow the planting to bloom and ripen hard seed, and it returns as a weedy volunteer, surfacing in whatever you set out afterward. Timing settles it. Mow, till, or roll the stand down at or before early bloom, ahead of any viable seed, and turn under or pull anything that has already gone to seed.
Fix:
- Mow, till, or roll to terminate at or before early bloom, before viable seed forms
- Remove or incorporate any plants that have already set seed
Drooping plants, gnawed roots, or sticky leaves
More than one trouble can land at the same time. Clover root curculio larvae work over the roots and nodules, crown and root rots or Sclerotinia move in on damp fall plantings, and aphids and thrips gather on the foliage and flower heads. Look over the roots for chewing and rot and the leaves for insects, then count on a well-drained spot and a rotation to keep things in check, since a cover crop does not have to be flawless.
Fix:
- Plant on well-drained soil and avoid waterlogged sites
- Rotate away from legumes to break pest and disease cycles
- Tolerate minor feeding, since a cover crop need not be pest-free
Toxicity
Here is the reassuring part: crimson clover is not poisonous to pets, people, or wildlife. It is a legume forage that animals graze with no worry. The single qualifier touches grazing ruminants, where lush stands can lead to bloat under poor management, a question of how the grazing is run rather than any poison in the plant.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Because it does not appear on the ASPCA toxic-plant lists, a cat that takes a curious bite has nothing to fear. A large helping of any unfamiliar green can leave a delicate stomach unsettled for a day, as always.
Dogs None
A dog can live alongside it and sample it freely. Should one help itself to a big serving, the most you are likely to notice is a loose stool that settles on its own.
Horses Safe
For horses this is good, safe grazing. The clover that gives them trouble is the related alsike, not this one, so a pasture with crimson clover is nothing to fret over.
Rabbits Safe
Rabbits can browse it with no harm, and it serves as a pleasant fresh green. Bring any new forage in slowly so their digestion has room to settle into it.
Livestock Mild
Cattle and sheep take to it readily and do well on it, with a single caveat: grazing lush, quick-growing stands hard can set off pasture bloat. Keep the grazing in hand and the risk stays slight.
Birds Safe
Both the seeds and the soft new growth are safe for birds, and chickens will gladly work a stand over. Nothing about the plant puts them at risk.
People Safe
It holds no poison for people. The flowers and sprouts carry a long tradition of use, though clover pollen can act as a mild allergen for some.
Safe around pets and people. Like other clovers and legumes, lush crimson clover can cause bloat in ruminant livestock (cattle and sheep) if grazed heavily, but it is not poisonous to pets or people. Note that some related Trifolium species (for example alsike clover) can cause photosensitization or liver problems in horses, and clover pollen can be a mild allergen.
Varieties
Most crimson clover on offer is common seed, yet a handful of named selections deserve a look, chiefly for cold hardiness and dependable reseeding.
Dixie
A southern staple valued for dependable hard-seed reseeding, which lets the planting renew itself across mild-winter regions.
AU Robin
An improved, more cold-tolerant release that flowers and finishes ahead of standard types, a genuine edge in marginal zones.
AU Sunrise
A second early-finishing, hardier selection developed for sooner bloom and a broader range of adaptation.
Kentucky Pride
A naturalized, self-renewing pick at home in the upper South and across the transition zone between warm and cool climates.
Companions
Plant near
cereal rye: Grass-legume cover crop mix; the rye adds biomass and scavenges nitrogen while the clover fixes nitrogen and suppresses weeds.
oats: Oats provide quick fall cover and a nurse crop while crimson clover establishes and fixes nitrogen.
corn: Crimson clover green manure releases fixed nitrogen for a following heavy feeder such as corn.
How to propagate
There is only one way to bring crimson clover along, from seed sown straight into the soil. The part that asks for care is the inoculant, not the sowing.
SeedEasy
Late summer to fall (6-8 weeks before first frost) to overwinter, or early spring in cold areas · Germinates in about 1-2 weeks; establishes a stand within several weeks of sowing
There is just one route with this plant: seed, dropped directly into the soil. Set it about 1/4 inch deep in a firm, moist bed, and reach for pre-inoculated seed, or dress it yourself with Rhizobium inoculant, so the roots build their nitrogen-fixing nodules. Sprouting takes roughly one to two weeks, a stand knits together over the next several weeks, and the timing falls to late summer or fall to overwinter, or early spring where it gets cold.
Myths
Any clover will do the same job, so crimson clover is interchangeable with white or red clover.
Quick, eye-catching, and nitrogen-fixing it may be, yet this annual runs shorter and less winter-hardy than the perennial white or red clovers. Its place is the fast fall or spring cover and green manure, taken down before seed set. Think of it as a single-season worker, not a lasting pasture clover.