Ornamental · Fabaceae
Crimson Clover
Trifolium incarnatum
Sow it in fall and crimson clover repays you with fixed nitrogen and a sweep of brilliant red bloom.
Full sun
Every 5–10 days
150–210 days
USDA 6–9
Overview
Crimson clover is a quick cool-season legume valued for what it accomplishes rather than its looks, though it manages both. Belonging to the pea family, it draws nitrogen from the air and banks it in its roots, the reason growers and farmers plant it as a cover crop and green manure. While it works, it grows fast, crowds out weeds, and feeds bees.
The plant is annual, and a brief one at that. After a late-summer or fall sowing it settles into a low rosette before winter, then surges upward in spring to raise brilliant crimson-red conical flower heads before seeding and dying. That pace is the whole appeal: one season delivers both cover and fertility, after which you turn it under for the next crop.
Its real strength is the handoff. Terminate it at or just shy of bloom and a pulse of nitrogen releases exactly as a hungry follow-on crop such as corn needs it. Leave it standing too long and it forms hard seed, returning as a volunteer weed in next season'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 mostly handed off to rainfall, with termination at or before early bloom.
Light
Crimson clover performs best in full sun, where growth and bloom are strongest, though it tolerates partial sun. Under heavy shade it grows thin and sprawling and fixes less nitrogen, since reduced light limits the photosynthesis that powers nodule activity, so site it in the open.
Water
Hold the seedbed moist through germination and establishment, then water only during dry spells, because a settled stand draws mostly on rainfall. What it will not tolerate is standing water, which suffocates the roots, so steer clear of soggy or waterlogged ground.
Soil
Give it well-drained loam or sandy loam of moderate fertility. Heavy clay or waterlogged ground holds too much water for its roots, so it falters there, and it prefers a near-neutral pH of 6.0 and 7.0 where nutrients stay most available.
Temperature
This cool-season plant copes across a broad span, from about 10°F to 84°F (-12°C to 29°C), though its cold hardiness lags behind other clovers. Hard freezes in cold zones can thin or kill an overwintering stand outright.
Humidity
Everyday outdoor humidity suits it, so there is no figure to chase. Air movement and drainage carry more weight, because cool, wet, crowded stands are what set up the crown and root rots.
Feeding
Being a nitrogen-fixing legume, it requires no nitrogen fertilizer; instead, inoculate the seed with the proper Rhizobium so the roots form nodules and supply their own. Add phosphorus or potassium only when a soil test confirms a genuine shortage.
Pruning
Conventional pruning does not apply. The real task is termination: mow, till, roll, or let it winterkill at or before early bloom, ahead of hard-seed set, then work it in as green manure or leave it on top as mulch.
Repotting
none
Size & spacing
A stand reaches about 12 to 35 inches (30 to 90 cm) tall, with single plants spreading roughly 6 to 12 inches (15 to 30 cm). It goes in broadcast or drilled as a dense stand, not transplanted as spaced individuals.
When to plant
Crimson clover keys off the cool season. Put it down in late summer to fall, roughly 6 to 8 weeks before your first frost, so it forms a crown that overwinters in mild zones; where winters are harder, sow in early spring instead. Bloom follows the next spring, and termination happens at or just before it.
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 crimson clover problem comes down to how the stand went in or when it came out. Learn to read the early cues in the canopy and the roots, and you can patch a thin spot or stop a weedy reseed before it costs you. Find your match below, then act while action still pays.
Stand comes up thin and pale, with feeble growth
When the seed missed its Rhizobium inoculant, no root nodules form, nothing fixes nitrogen, and the plants stay pale and starved. Dry soil and loose seed-to-soil contact thin the count on top of that. Lift a few seedlings a couple of weeks past emergence to check for pink, working nodules, then drill fresh inoculated seed into a firm, moist bed across the bare ground.
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
Winter kills back the stand before spring
Because crimson clover is less cold-hardy than other clovers, hard freezes can take it out, particularly below about zone 6. Sow too late and the crowns never bulk up enough to carry through the cold. Use any winterkilled residue as mulch or green manure; in cold country, run it as a spring-sown annual or step up to tougher releases 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
Self-sown plants invade the next planting
Allow the crop to flower and ripen hard seed, and crimson clover becomes a weedy volunteer that sprouts in whatever bed comes after it. Termination timing is the whole answer. Mow, till, or roll the stand at or before early bloom, ahead of viable seed, and dig out or bury any plants that already carry mature 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
Wilting, chewed roots, or sticky leaves from pests and rot
More than one offender can show up together. Clover root curculio larvae gnaw the roots and nodules, crown and root rots or Sclerotinia take hold on wet fall sowings, and aphids and thrips work the foliage and flower heads. Inspect the roots for feeding and rot and the leaves for insects, then rely on well-drained ground and crop rotation, because a cover crop does not have to be flawless to do its job.
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 reassuring: crimson clover is not poisonous to pets, people, or wildlife. It is a legume forage that animals graze safely. The single real caveat applies to grazing ruminants, where lush stands can bring on bloat under poor management, a grazing matter rather than a case of poisoning.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Because this plant is absent from the ASPCA toxic-plant lists, a cat that samples a leaf faces no toxic risk. A large bite of any unfamiliar green can still leave a sensitive stomach unsettled for a day.
Dogs None
Dogs can be around it and taste it safely. If one wolfs down a big serving in one go, expect at most some loose stool that resolves without help.
Horses Safe
For horses, crimson clover is sound, safe forage. The species that gives horses trouble is the related alsike clover, not this one, so there is no concern with this plant.
Rabbits Safe
Crimson clover is harmless for rabbits to graze and serves as a good fresh green. Bring any new forage in slowly so their digestion can adjust to it.
Livestock Mild
Cattle and sheep take to crimson clover well and do well on it, with one proviso: heavy grazing of lush, fast-growing stands can set off pasture bloat. Control the grazing and the risk stays minimal.
Birds Safe
Seeds and soft growth are harmless to birds, and chickens will gladly work over a stand. None of the plant threatens them.
People Safe
For people, crimson clover carries no poison. Its flowers and sprouts have been used for a long time, although clover pollen acts 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
Common seed makes up most crimson clover for sale, yet a handful of named types are worth knowing, chiefly for cold hardiness and dependable reseeding.
Dixie
A southern mainstay valued for dependable hard-seed reseeding, which lets the stand regenerate itself where winters stay mild.
AU Robin
An improved selection with better cold tolerance that flowers and matures ahead of standard types, a genuine edge in marginal zones.
AU Sunrise
A second hardier, quick-maturing cultivar developed for earlier bloom and broader adaptation.
Kentucky Pride
A naturalized, self-reseeding line fitted to the upper South and 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 exactly one way to grow crimson clover, from seed dropped directly into the soil. The inoculant is the part to get right, not the sowing itself.
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 way to start crimson clover, and it goes straight into the soil. Direct-sow at about 1/4 inch deep into a firm, moist seedbed using pre-inoculated seed, or coat it with Rhizobium inoculant, so the roots can build nitrogen-fixing nodules. Expect germination in roughly one to two weeks and a filled-in stand within several weeks, timed for late summer to fall to overwinter or for early spring in cold areas.
Myths
Any clover will do the same job, so crimson clover is interchangeable with white or red clover.
Crimson clover is a quick, eye-catching annual that fixes nitrogen, yet it carries less winter hardiness and a shorter life than perennial white or red clover. Its main role is a fast fall or spring cover crop and green manure that you terminate before seed set. Treat it as a one-season workhorse, not a long-lived pasture clover.