Ornamental · Fabaceae
Crimson Clover
Trifolium incarnatum
Tuck it in come fall, and crimson clover rewards you with free nitrogen and a glowing carpet of red bloom.
Full sun
Every 5–10 days
150–210 days
USDA 6–9
Overview
Crimson clover is a quick cool-season legume you grow mostly for what it does, even though it happens to be lovely too. Being part of the pea family, it draws nitrogen from the air and tucks it away in its roots, which is exactly why gardeners and farmers count on it as a cover crop and green manure. It comes up fast, crowds out weeds, and keeps the bees happy the whole time it is at work.
Keep in mind that it is an annual, and a brief one at that. Sow it in late summer or fall and it settles into a low rosette before the cold sets in, then springs upward to lift brilliant crimson-red conical flower heads before it seeds and finishes its run. That swiftness is exactly what you want: cover and fertility arrive in one season, ready to turn under for whatever crop comes next.
The handoff is where it really earns its place. End the stand at or just before bloom and a wave of nitrogen is freed right when a hungry follow-on crop such as corn is ready for it. Leave it going too long, though, and it forms hard seed that can volunteer into next year's bed.
Care
The short version: give it full sun and well-drained soil, direct-sow inoculated seed about 1/4 inch deep into a firm, moist bed, water it through establishment and then mostly let the rain take over, and terminate it at or before early bloom. You truly have room to get this right.
Light
Crimson clover does its best in full sun, where growth and bloom come on strong, though it will get by in partial sun. Give it too much shade and it turns thin and floppy and fixes less nitrogen, so an open, sunny spot is the kind thing to offer it.
Water
Keep the seedbed moist while it germinates and settles in, then ease off and water only during dry stretches, because an established stand mostly drinks from the rain. The one thing it really cannot abide 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 will hold it back, and it is happiest at a near-neutral pH between 6.0 and 7.0.
Temperature
This is a cool-season grower that copes with a generous span, somewhere from 10°F to 84°F (-12°C to 29°C), though it is less cold-hardy than other clovers. In cold zones a hard freeze can thin or end an overwintering stand.
Humidity
Everyday outdoor humidity suits it just fine, so there is no number to chase. What counts more is good airflow and drainage, since cool, damp, crowded conditions are what tempt the crown and root rots to move in.
Feeding
Being a nitrogen-fixing legume, it asks for no nitrogen fertilizer at all; you simply inoculate the seed with the right Rhizobium and let the plants make their own. Reach for phosphorus or potassium only if a soil test points to a genuine shortfall.
Pruning
Pruning in the ordinary sense 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 lying as surface mulch.
Repotting
none
Size & spacing
A stand reaches roughly 12 to 35 inches (30 to 90 cm) tall, with each plant spreading around 6 to 12 inches (15 to 30 cm). You broadcast or drill it as a thick stand rather than spacing out individual plants.
When to plant
Crimson clover keeps to the cool season, and the rhythm is easy to follow. Sow it in late summer to fall, around 6 to 8 weeks before your first frost, so it builds a crown to carry through winter in mild zones; where it runs colder, wait and sow in early spring. Flowering arrives the next spring, and that is your cue to 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
Nearly every crimson clover hiccup comes down to how the stand went in or when it was ended, and that is reassuring, because both are within your control. Learn to read the early clues in the plants and the roots, and you can patch a thin spot or stop a weedy reseed before it adds up to much. Find what matches below, then step in while it still does some good.
When the stand comes up thin and the leaves look pale
Take heart, because this one is almost always fixable. Pale, sluggish plants usually point to seed that missed its Rhizobium inoculant, which means no root nodules formed and nothing is feeding the plants nitrogen. Dry soil and loose seed contact can thin things out too. A few weeks after the seedlings appear, dig up a handful and check the roots for pink, working nodules, then simply resow the bare spots with fresh inoculated seed pressed into firm, damp soil.
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
When winter thins or wipes out the stand
Do not be discouraged if cold weather takes a toll. This clover is less cold-hardy than its clover cousins, so it can winterkill where freezes get severe, especially below about zone 6. Sowing late leaves the crowns too small to make it through. Anything the cold claims still earns its keep as mulch or green manure, and in chilly spots you can simply grow it as a spring-sown annual or reach for tougher types like 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
When it shows up uninvited in next year's bed
If you let it flower and set hard seed, crimson clover can turn into a cheerful volunteer that sprouts up wherever you plant next. The good news is that timing is all it takes to stay ahead of it. Mow, till, or roll the stand at or before early bloom, before any viable seed forms, and gently pull or turn under anything that already managed 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
When wilting, root trouble, or sticky leaves show up
A few pests and rots can turn up here, and that is normal for a cover crop. Clover root curculio grubs nibble the roots and nodules, crown and root rots or Sclerotinia can settle into damp fall plantings, and aphids or thrips may gather on the leaves and flower heads. Have a look at the roots for chewing and rot and the leaves for insects, then lean on good drainage and crop rotation. A little feeding damage is perfectly fine, so there is no need to chase a flawless stand.
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 comforting part: crimson clover is not poisonous to pets, people, or wildlife. It is a legume forage that animals graze with no harm. The single caveat involves grazing ruminants, where lush stands can bring on bloat if managed carelessly, and that is a grazing matter rather than a poisoning.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
You can relax if a cat samples a leaf, because crimson clover is absent from the ASPCA toxic-plant lists and poses no threat. A large helping of any unfamiliar green might briefly unsettle a tender tummy for a day, and that passes.
Dogs None
Dogs are welcome to be near it and to have a taste. Should one wolf down a big mouthful all at once, the most you would likely notice is a soft stool that sorts itself out.
Horses Safe
For horses, crimson clover is wholesome, safe forage. The cousin that gives horses grief is alsike clover, not this one, so you have nothing to fret about here.
Rabbits Safe
Rabbits can browse crimson clover safely, and it makes a lovely fresh treat. Just ease any new forage in slowly so their digestion has time to settle.
Livestock Mild
Cattle and sheep take to crimson clover eagerly and do well on it, with a single thing to watch: grazing lush, fast-growing stands too hard can bring on pasture bloat. Pace the grazing and the worry stays small.
Birds Safe
Birds are fine with the seeds and soft new growth, and chickens will gladly pick through a stand. Nothing about the plant puts them at risk.
People Safe
People have nothing to fear from crimson clover, as it is not poisonous. Its flowers and sprouts have been enjoyed for ages, though a few people 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 you will find is sold as common seed, but a handful of named types are nice to know, chiefly for their cold hardiness and their knack for coming back from seed.
Dixie
A southern favorite many growers lean on for its dependable hard-seed reseeding, which lets the stand return on its own where winters stay gentle.
AU Robin
A bred-up, cold-tougher release that flowers and finishes ahead of the standard kinds, which is genuinely helpful where conditions are borderline.
AU Sunrise
One more hardy, quick-finishing cultivar developed for earlier flowering and a broader range of places it will thrive.
Kentucky Pride
A naturalized, self-reseeding pick at home in the upper South and the in-between zone where warm and cool climates meet.
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 keeps things wonderfully simple, since it is grown a single way, from seed dropped straight into the ground. The part to mind is the inoculant, 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
There is just one path with crimson clover, and it is a forgiving one: seed sown right into the soil. Scatter or drill it about 1/4 inch deep into a firm, damp seedbed, and either start with pre-inoculated seed or coat it yourself with Rhizobium inoculant so the plants grow their nitrogen-fixing nodules. Sprouting takes roughly one to two weeks, the stand knits together over the following few weeks, and you aim for late summer to fall to carry it through winter, 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.
Think of crimson clover as a quick, eye-catching annual that fixes nitrogen yet is shorter-lived and less winter-tough than the perennial white or red kinds. Its real calling is a speedy fall or spring cover crop and green manure, wrapped up before seed forms. Lean on it as a single-season helper, not a lasting pasture clover.