Crimson Clover as Cover Crop and Green Manure
Those brilliant scarlet fields you see in spring? That’s crimson clover — an annual legume that’s one of the best nitrogen-building cover crops available. It’s not a lawn plant and it isn’t red clover. Here’s how to use it to feed your soil.
- Species: Trifolium incarnatum (annual)
- Height: 1–3 ft; scarlet flower spikes
- Use: Cover crop / green manure / forage
- Nitrogen: ~30–60 lb/acre (more at bloom)
- Seeding: 15–18 lb/ac drilled, 22–30 broadcast
- Winter-annual zone: S. PA and south
- Soil/pH: Well-drained loam, 5.5–7.0
- Pet-safe: Yes (non-toxic)
What crimson clover is
Crimson clover (Trifolium incarnatum) is an annual legume grown as a cover crop and green manure — not a lawn plant. It grows 1–3 feet tall with unmistakable brilliant scarlet-red flower spikes, grows rapidly in cool weather, tolerates shade, and completes its whole life cycle in a single season. It’s often confused with red clover, but it’s a different plant: crimson has taller flower stems, faster growth, and larger seeds, and unlike red clover it does not frost-seed well.
Why it’s a top cover crop
Crimson clover’s main job is fixing nitrogen and building soil. Fall-planted, spring-killed stands commonly supply a nitrogen credit of roughly 30–60 lb per acre (and considerably more if grown to full bloom), while suppressing weeds, adding organic matter, and reducing erosion. Thanks to its shade tolerance and reseeding, it’s a favorite living cover in orchards and vineyards, and a proven nitrogen source ahead of crops like corn. It’s also a spectacular spring pollinator and nectar plant when allowed to flower.
Winter annual vs summer annual (by region)
| Region | How to use it |
|---|---|
| Southern PA and south (east of Mississippi) | Winter annual: sow late summer/fall, overwinter, terminate in spring |
| Colder northern regions (zone 5 and colder) | Tends to winter-kill without snow cover — spring-sow as a summer annual instead |
| Buffered pockets (Finger Lakes, coastal NE) | May overwinter where lake/ocean effect insulates |
The reliable winter-annual “crimson clover zone” runs east of the Mississippi from about southern Pennsylvania south. Farther north it usually winter-kills unless snow insulates it, so growers there sow it in spring as a summer annual for a fast flush of biomass and nitrogen.
How to grow crimson clover
For winter-annual use, seed six to eight weeks before your first average frost so it establishes before cold. Rates: 15–18 lb per acre drilled or 22–30 lb broadcast, placed 1/4–1/2 inch deep in well-drained loam around pH 5.5–7.0. Inoculate the seed with the correct Rhizobium if a true clover hasn’t grown in the field recently. Avoid poorly drained soils (disease risk). For a summer annual, sow in spring once frost danger passes.
Terminating it for nitrogen
To capture the most nitrogen, terminate at full bloom — mow, roll, or incorporate (disk) the stand. If you’re following with a planted crop, wait two to three weeks after killing before seeding, so the residue breaks down and the flush of decomposition pathogens settles. If you want it to reseed itself (common in orchards), grow a hard-seeded variety and let it set seed before termination — it’ll re-establish the next fall.
Crimson clover vs red clover
These two get mixed up constantly because of their red-associated names, but they’re different plants with different jobs. Crimson clover is a true annual with tall scarlet spikes, faster growth, and larger seeds — a one-season cover crop. Red clover is a short-lived perennial (2–3 years) with pink-purple globe flowers that frost-seeds well and persists longer. For a fast winter or summer green-manure boost, crimson wins; for a longer-lived meadow or forage stand, red clover fits.
Is it right for you? (a quick fit-check)
Great fit if: you want to build soil and fix nitrogen fast in a garden bed, orchard, vineyard, or crop rotation — sown as a winter annual in mild regions or a summer annual up north. Its bloom is a bonus for pollinators.
Not the right plant if: you want a permanent, mowable lawn — crimson is a tall annual that dies after flowering, so it can’t make turf. For a lawn clover, use low white Dutch clover or microclover instead.
The verdict
Crimson clover is one of the most useful cover crops you can plant: a fast, nitrogen-rich, weed-suppressing annual that builds soil and feeds pollinators, all in a single season. Sow it as a winter annual from southern Pennsylvania south, or as a spring-sown summer annual farther north where it winter-kills, and terminate it at bloom to bank the most nitrogen. Just don’t mistake it for a lawn plant or for red clover — it’s its own thing, and for soil-building it’s hard to beat. For a permanent lawn, reach for white Dutch clover instead.
Frequently asked questions
What is crimson clover used for?
It’s an annual cover crop and green manure: it fixes nitrogen (~30–60 lb/acre, more at bloom), suppresses weeds, builds organic matter, and reduces erosion. It’s used ahead of crops like corn, as a living cover in orchards and vineyards, as forage, and as a spring pollinator plant. It’s not a lawn plant.
Is crimson clover an annual or perennial?
An annual — it completes its life cycle in one growing season and dies after flowering and setting seed. Sown in fall it grows as a winter annual (in mild regions), overwintering and blooming in spring; sown in spring it grows as a summer annual. Hard-seeded varieties can reseed themselves, which mimics persistence in orchards.
When do you plant crimson clover?
For winter-annual use, seed six to eight weeks before your first average frost so it establishes before cold. For summer-annual use (colder regions where it winter-kills), sow in spring once frost danger passes. Drill at 15–18 lb/acre or broadcast at 22–30, 1/4–1/2 inch deep in well-drained loam at pH 5.5–7.0, inoculated.
How is crimson clover different from red clover?
Crimson clover is a true annual with tall scarlet flower spikes, faster growth, and larger seeds — a one-season cover crop that doesn’t frost-seed well. Red clover is a short-lived perennial (2–3 years) with pink-purple globe flowers that frost-seeds well and persists longer. Different plants, different jobs, despite the similar names.
How do you terminate crimson clover?
Mow, roll, or incorporate it at full bloom for maximum nitrogen. If planting a crop afterward, wait two to three weeks so the residue breaks down and the decomposition-pathogen flush settles. To let it reseed (e.g., in orchards), grow a hard-seeded variety and let it set seed before termination.
Is crimson clover safe for pets?
Yes — as a Trifolium (true clover), crimson clover is non-toxic and pet-safe, safe for dogs and cats to walk through or nibble. (Note that when grazed heavily by livestock, like many lush legumes it can cause bloat, but that’s a ruminant concern, not a dog or cat one.) It’s a safe plant to have around a pet-friendly garden.
Match the clover to the job
Crimson clover builds soil; for a permanent lawn use pet-safe white Dutch clover or a microclover-fescue blend. Crimson is a cover crop, not turf — see the red clover guide for the other meadow clover.
Species characteriztics, cover-crop use, seeding, and termination cross-checked against MSU Extension, Mississippi State Extension, and USDA NRCS.
A single species is an ingredient. The blend is the answer.
Trileaf Three Clover Lawn Mix — T. repens + T. pratense + T. incarnatum. Three-clover lawn. Buy the blend when the job needs more than one plant — the grass carries the wear, the clover feeds it, the flowers feed the bees. Buy the single species when you want one plant, one look, one job.
Sources
- MSU Extension — MSU Extension (what crimson clover is – a distinct annual cover-crop legume): crimson clov
- Mississippi State Extension — Mississippi State Extension (how and when to grow it, by region): for winter-annual use, s
- USDA NRCS — USDA NRCS / consensus (termination, pollinator value, and pet safety): terminate crimson c