Ornamental · Fabaceae
Crimson Clover
Trifolium incarnatum
Sow it in fall and crimson clover pays you back with fixed nitrogen and a sheet of brilliant red bloom.
Full sun
Every 5–10 days
150–210 days
USDA 6–9
Overview
Crimson clover is a fast cool-season legume grown more for what it does than how it looks, though it does both well. As a member of the pea family it pulls nitrogen out of the air and stores it in its roots, which is why gardeners and farmers sow it as a cover crop and green manure. It grows quickly, smothers weeds, and feeds bees while it works.
It is an annual, and a short-lived one. Sown in late summer or fall, it puts on a low rosette before winter, then bolts up in spring to throw brilliant crimson-red conical flower heads before it sets seed and dies. That speed is the point: you get cover and fertility in a single season, then turn it under for the crop that follows.
Where it shines is the handoff. Terminate it at or just before bloom and you release a flush of nitrogen right when a hungry follow-on crop like corn can use it. Let it run too long and it sets hard seed, becoming a volunteer weed in 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 wants full sun for the strongest growth and bloom, though it takes partial sun. In too much shade it grows thin and floppy and fixes less nitrogen, so give it an open, sunny site.
Water
Keep the seedbed moist through germination and establishment, then water only in dry spells, since an established stand is largely rain-fed. The one thing it will not take is wet feet, so avoid soggy or waterlogged ground.
Soil
Plant it in well-drained loam or sandy loam of moderate fertility. It struggles on heavy clay or waterlogged ground, and it likes a near-neutral pH between 6.0 and 7.0.
Temperature
This is a cool-season plant that handles a wide range, from about 10°F to 84°F (-12°C to 29°C), though it is less cold-hardy than other clovers. Hard freezes in cold zones can thin or kill an overwintering stand.
Humidity
Ordinary outdoor humidity suits it fine, so there is no target to hit. Air movement and drainage matter more, since cool, wet, crowded conditions are what invite the crown and root rots.
Feeding
As a nitrogen-fixing legume it needs no nitrogen fertilizer; instead, inoculate the seed with the right Rhizobium so the plants fix their own. Add phosphorus or potassium only if a soil test shows a real shortfall.
Pruning
There is no pruning in the usual sense. The job is termination: mow, till, roll, or let it winterkill at or before early bloom, ahead of hard-seed set, then turn it in as green manure or leave it as surface mulch.
Repotting
none
Size & spacing
A stand stands about 12 to 35 inches (30 to 90 cm) tall, with individual plants spreading roughly 6 to 12 inches (15 to 30 cm). It is broadcast or drilled as a dense stand rather than set out as spaced plants.
When to plant
Crimson clover runs on the cool season. Sow it in late summer to fall, about 6 to 8 weeks before your first frost, so it establishes a crown to overwinter in mild zones; in colder areas sow in early spring instead. Bloom comes the following spring, and you terminate 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
Most crimson clover problems trace back to how the stand was sown or when it was terminated. Read the early signs in the stand and the roots, and you can fix a thin patch or head off a weedy reseed before it costs you. Match what you see below, then act while it still helps.
Thin, patchy stand with pale, weak growth
Pale, struggling plants almost always mean the seed never got its Rhizobium inoculant, so no root nodules formed and nothing is fixing nitrogen. Dry soil and poor seed-to-soil contact thin the stand further. Dig a few seedlings a few weeks after they emerge and look for pink, active nodules, then reseed bare patches with fresh inoculated seed 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
Stand thins or dies out over winter
Crimson clover is less cold-hardy than other clovers and can winterkill where freezes run hard, especially in zones colder than about 6. Sowing too late leaves the crowns too small to survive. Treat any winterkilled residue as mulch or green manure, and in cold areas grow it as a spring-sown annual or switch to hardier 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
Volunteers reseed into the next crop
Left to flower and set hard seed, crimson clover turns into a weedy volunteer that pops up in whatever you plant next. The fix is timing. Mow, till, or roll to terminate the stand at or before early bloom, before viable seed forms, and pull or turn under any plants that already set 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, root damage, or sticky foliage from pests and rots
Several culprits can hit at once here. Clover root curculio larvae chew the roots and nodules, crown and root rots or Sclerotinia set in on wet fall plantings, and aphids and thrips pile onto the foliage and flower heads. Check roots for chewing and rot and the leaves for insects, then lean on well-drained sites and crop rotation, since a cover crop need not be pest-free.
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
Good news on this one: crimson clover is not poisonous to pets, people, or wildlife. It is a legume forage that animals graze safely. The only real caveat is for grazing ruminants, where lush stands can cause bloat if managed poorly, which is a grazing issue rather than a poisoning.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Crimson clover is not on the ASPCA toxic-plant lists, so a cat that nibbles a leaf is in no danger. A big mouthful of any new green can still upset a sensitive stomach for a day.
Dogs None
Safe for dogs to be around and to taste. The worst you might see from a dog that gobbles a lot at once is some loose stool that clears on its own.
Horses Safe
Crimson clover itself is good, safe forage for horses. It is the related alsike clover, not this plant, that causes horses trouble, so there is nothing to worry about here.
Rabbits Safe
Rabbits can graze crimson clover without harm, and it makes a fine fresh green. Introduce any new forage gradually so their gut has time to adjust.
Livestock Mild
Cattle and sheep graze crimson clover readily and thrive on it, with one catch: heavy grazing of lush, fast-growing stands can trigger pasture bloat. Manage the grazing and the risk stays low.
Birds Safe
The seeds and tender growth are safe for birds, and chickens will happily forage a stand. No part of the plant poses a risk to them.
People Safe
Crimson clover is not poisonous to people. The flowers and sprouts have a long history of use, though some folks find clover pollen a mild allergen.
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 sold is common seed, but a few named types are worth knowing, mainly for cold hardiness and reliable reseeding.
Dixie
A widely grown southern type prized for reliable hard-seed reseeding that brings the stand back on its own in mild-winter regions.
AU Robin
An improved, cold-hardier release that blooms and matures earlier than standard types, a real advantage in marginal zones.
AU Sunrise
Another early-maturing, hardier cultivar bred for earlier bloom and wider adaptation.
Kentucky Pride
A naturalized reseeding selection suited 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
Crimson clover is grown one way and one way only, from seed sown straight into the ground. The catch 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
Crimson clover grows only from seed, sown straight into the ground. Direct-sow about 1/4 inch deep into a firm, moist seedbed and use pre-inoculated seed, or treat it with Rhizobium inoculant, so the plants form nitrogen-fixing nodules. Seed germinates in roughly one to two weeks and fills in a stand within several weeks, timed for late summer to fall to overwinter or 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 fast, showy annual that fixes nitrogen but is less winter-hardy and shorter-lived than perennial white or red clover. You grow it mainly as a quick fall or spring cover crop and green manure, terminated before seed set. Treat it as a one-season workhorse, not a long-lived pasture clover.