Ornamental · Fabaceae
Crimson Clover
Trifolium incarnatum
Sow it in fall and crimson clover repays you with fixed nitrogen and a sweep of glowing red heads.
Full sun
Every 5–10 days
150–210 days
USDA 6–9
Overview
Crimson clover is a quick cool-season legume earning its keep through what it does as much as how it looks, and it does both. Belonging to the pea family, it draws nitrogen from the air and banks it in the roots, the reason gardeners and farmers set it as a cover crop and green manure. The trefoil foliage fills in fast, shades out weeds, and draws bees while the plant works.
Its life is annual and brief. Sown across late summer or fall, the plant hugs the ground in a low rosette through winter, then shoots upward in spring and lifts brilliant crimson-red conical flower heads, tall and tapered, before it seeds and dies. The pace is the whole point: a single season delivers cover and fertility, and then you turn the foliage under for the crop that comes next.
The handoff is where it earns its place. Cut it down at or just before bloom and a surge of nitrogen frees up exactly when a hungry follow-on crop such as corn can take it in. Let it linger and the heads harden into hard seed, leaving volunteer plants scattered through next year's bed.
Care
The short version: full sun and well-drained soil, inoculated seed direct-sown about 1/4 inch deep into a firm, moist bed, watered through establishment and then left mostly to the rain, and terminated at or before early bloom.
Light
Crimson clover reaches for full sun, which builds the densest foliage and the brightest heads, though it gets by in partial sun. Crowd it into too much shade and the stems run thin and floppy and the plant fixes less nitrogen, so give it open, sunny ground.
Water
Hold the seedbed moist through germination and establishment, then water only during dry spells, since a settled stand leans on the rain. The single thing it refuses is wet feet, so steer clear of soggy or waterlogged ground.
Soil
Set it into well-drained loam or sandy loam of moderate fertility. Heavy clay or waterlogged ground stalls it, and it prefers a near-neutral pH between 6.0 and 7.0.
Temperature
A cool-season plant, it copes across a broad span, roughly 10°F to 84°F (-12°C to 29°C), yet it carries less cold hardiness than other clovers. Deep freezes on cold ground can thin or finish an overwintering stand.
Humidity
Plain outdoor humidity suits it, so there is no figure to chase. Air movement and drainage count for more, because cool, wet, crowded foliage is what brings on the crown and root rots.
Feeding
Being a nitrogen-fixing legume, it asks for no nitrogen fertilizer; coat the seed with the right Rhizobium instead so the plants supply their own. Reach for phosphorus or potassium only when a soil test points to a true 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 rises about 12 to 35 inches (30 to 90 cm) tall, with single plants spreading near 6 to 12 inches (15 to 30 cm). Broadcast or drill it as a thick stand rather than setting out spaced plants.
When to plant
Crimson clover keeps to the cool season. Set the seed across late summer to fall, about 6 to 8 weeks ahead of your first frost, so the plant builds a crown to carry through winter in mild zones; on colder ground, sow in early spring instead. The red heads open the following spring, and termination lands at or just before that.
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
Almost every crimson clover problem comes down to how the stand went in or when it came down. Read the early tells in the foliage and the roots and you can patch a thin spot or stop a weedy reseed before it costs you. Find what matches below, then act while there is still time to help.
Pale, washed-out leaves over a thin, gappy stand
When the foliage comes up sickly and yellow-green instead of deep, healthy green, the seed almost certainly missed its Rhizobium inoculant, leaving the roots bare of the nodules that feed the plant nitrogen. Dry ground and loose seed contact widen the gaps. A few weeks after the seedlings break through, lift a couple and look along the roots for small pink nodules, then drop fresh inoculated seed into the bare spots over a firm, damp 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
Low winter rosettes brown off and vanish by spring
Those flat winter rosettes are less cold-hardy than other clovers, and a run of deep freezes can brown them out and kill them, mostly in zones below about 6. Plants set out too late never build a crown wide enough to pull through. Let any frozen residue lie as mulch or work it in as green manure, and in cold ground sow it fresh each spring or reach for tougher 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
Hard seed sprouts up through next season's bed
Once the conical red heads finish flowering and harden into seed, crimson clover turns weedy and volunteer, sending up scattered clover seedlings among whatever follows. Timing settles it. Cut, till, or roll the stand down at or before early bloom, before any seed turns viable, and dig out or bury the few plants that already carry 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 stems, gnawed roots, and tacky leaves
More than one pest can crowd in at once. Clover root curculio grubs gnaw at the roots and nodules, crown and root rots or Sclerotinia take hold in soggy fall plantings, and aphids and thrips cluster over the leaves and the red flower heads. Pull a plant to check the roots for chewing and rot and scan the foliage for insects, then rely on dry, well-drained ground and rotation, since a cover crop does not have to be spotless.
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
The verdict here is easy: crimson clover is not poisonous to pets, people, or wildlife. As a legume forage, animals graze it safely. The lone caveat falls on grazing ruminants, where rank, lush stands can bring on bloat under poor management, a grazing concern and not a poisoning.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
None of this plant appears on the ASPCA toxic-plant lists, so a cat that bites off a soft trefoil leaf faces no danger. A big mouthful of any unfamiliar green can still leave a sensitive stomach unsettled for a day.
Dogs None
Dogs are safe nosing around the foliage and sampling a leaf. The most a dog that wolfs down a clump might show is a bout of loose stool that passes on its own.
Horses Safe
For horses, crimson clover itself is sound, safe forage. Trouble traces to the related alsike clover rather than this plant, so the red-headed clover in the field gives no cause for concern.
Rabbits Safe
Rabbits can browse the soft clover leaves without harm, and it serves as a good fresh green. Bring any new forage in slowly so their gut has time to settle into it.
Livestock Mild
Cattle and sheep take to the lush, fast-growing foliage readily and do well on it, with one catch: grazing the rank growth too hard can set off pasture bloat. Keep the grazing in check and the risk stays small.
Birds Safe
Both the seeds and the tender shoots are safe for birds, and chickens will pick happily through a stand. Nothing on the plant threatens them.
People Safe
For people, crimson clover carries no poison. Its bright flowers and young sprouts have long seen culinary use, though clover pollen can be 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, but a handful of named types earn attention, chiefly for cold hardiness and steady reseeding.
Dixie
A southern favorite valued for dependable hard-seed reseeding, the kind of stand that returns under its own steam across mild-winter ground.
AU Robin
An improved, tougher release whose red heads open and ripen ahead of standard types, a genuine edge where winters bite.
AU Sunrise
A second early-maturing, hardier selection bred to flower sooner and fit a wider range of ground.
Kentucky Pride
A naturalized, self-reseeding pick at home in the upper South and the band that bridges 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 just one way to grow crimson clover: from seed sown straight onto the ground. The trick lies in the inoculant, not in 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
Seed is the only route, scattered right onto the ground. Direct-sow about 1/4 inch deep into a firm, damp seedbed and reach for pre-inoculated seed, or coat it with Rhizobium inoculant, so the roots throw the nodules that fix nitrogen. The seed sprouts in roughly one to two weeks and knits into a stand over several weeks, set for late summer to fall to overwinter or for early spring on cold ground.
Myths
Any clover will do the same job, so crimson clover is interchangeable with white or red clover.
Crimson clover runs fast and flashy as an annual that fixes nitrogen, yet it stands less hardy through winter and lives a shorter life than the perennial white and red clovers. Its real role is a quick fall or spring cover crop and green manure, cut down before seed forms. Treat it as a one-season workhorse, not a long-lived pasture clover.