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Crimson Clover
Photo: "crimson clover" by Oregon State University · CC BY-SA 2.0

Crimson Clover

Annual · Fabaceae

Crimson clover is a cool-season legume cover crop used for nitrogen contribution, soil cover, erosion reduction, and pollinator bloom. It should be inoculated where needed, sown in the correct fall or cool-season window, and terminated before seed set unless reseeding is intentional. It is a winter annual. Key facts: 60–90 days to maturity, 6+ hours of sun. Not recommended for containers.

Updated June 1, 2026 · Backed by 3 cited sources
Overview

At a Glance

The essentials first: timing, light, spacing, seed-starting, container fit, and overall size.

Days to maturity
60–90 days
Sun
6+ hours
Container
Not recommended
Height
1–1.5 ft
at maturity
Planting window

Zone Planting Guide

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This card updates instantly with viability, frost timing, and any planting notes for your selected zone.

Resilience

Plant Health

Stress tolerance, resistance notes, and the most common problems to watch for as plants mature.

Tolerance
Heat: Medium Cold: Medium Drought: Medium

Watch for these first

Sort
Issue Severity Category Peak window
Crown rot Sclerotinia trifoliorum
High Disease May Peak window months: May.

Sclerotinia crown and stem rot on clovers, alfalfa, vetches, and related forage legumes. A cool, wet-season disease that can kill seedlings or wipe out patches after fall establishment, wet winters, or prolonged snow cover.

Triggers: Cool moist weather, fall seeding, wet soils, dense canopy, poor air circulation, and prolonged snow cover all favor disease.

Risk fades when: Drier conditions reduce active infection pressure, though stand damage may already be visible by spring.

Crown rot symptoms
Pathogen: Cercospora beticola — Photo: Plant pests and diseases · CC0 1.0
Damping off Pythium spp. / Rhizoctonia solani / Fusarium spp.
High Disease May–Aug Peak window months: May, Jun, Jul, Aug.

A seedling killer caused by several different fungi working together. It hits vegetables, flowers, herbs, microgreens, and cover-crop seedlings the same way — seeds rot before they emerge, or young seedlings collapse right at the soil line. Wet seed-starting mix and poor airflow in seedling trays are the classic conditions.

Triggers: Wet soil or starting mix, poor drainage, seedlings packed too tightly, contaminated trays or media, and stagnant air all favor damping-off.

Risk fades when: Drying the soil surface and improving airflow slows new spread. Collapsed seedlings don't recover, but the rest of the tray can be saved.

Damping off symptoms
Damping off of coffee seedlings caused by Fusarium sp. — Photo: Scot Nelson · CC0 1.0
Common leaf spot (clover & alfalfa) Pseudopeziza medicaginis, Pseudopeziza trifolii
Moderate Disease Summer Peak window months: Jun, Jul, Aug.

The most common leaf disease of alfalfa and clover cover crops. It makes small, dark brown to black circular spots with slightly fringed edges, often with a tiny raised fruiting disk in the center. Spots start on the lower leaves and move up, and infected leaves yellow and drop, thinning the stand. It is favored by cool, moist weather and is worst in spring and fall.

Triggers: The fungus overwinters in leaf debris and spreads by spores during cool, moist weather. Dry, warm summer weather slows it; cool, moist fall conditions favor a resurgence. A dense canopy that traps humidity raises risk.

Risk fades when: Dry, warm weather slows it. Two days above 82°F or three dry days exits the active window; spotted leaves stay damaged.

Common leaf spot (clover & alfalfa) symptoms
Pathogen: Cercospora beticola — Photo: Plant pests and diseases · CC0 1.0
Rust (clover & alfalfa) Uromyces striatus, Uromyces trifolii
Moderate Disease Summer Peak window months: Jun, Jul, Aug.

A rust of alfalfa and clover cover crops that makes small reddish-brown pustules on both leaf surfaces and sometimes on stems. The pustules rupture and release powdery spores, and heavy infection yellows and drops leaves, weakening the stand. It is favored by humid weather and extended leaf wetness.

Triggers: Favored by humidity and extended leaf wetness. Reddish-brown pustules on both leaf surfaces release powdery spores spread by wind. Often associated with nearby spurge as an alternate host.

Risk fades when: Hot or dry weather slows rust. Two days above 88°F or three dry days exits the active window; existing pustules remain.

Rust (clover & alfalfa) symptoms
Pathogen: Cercospora beticola — Photo: Plant pests and diseases · CC0 1.0
Feeding & picking

Nutrition & Harvest

How hungry the plant is, what ripe harvest looks like, and how long the crop keeps after picking.

Feeding
Nutrition
Feeding intensityLight feeder
Timing
Harvest

Early bloom to mid-bloom

Plant relationships

Companion Planting

Helpful neighbors can support growth or deter pests. Keep antagonistic plants separated to reduce stress and competition.

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What you'll need

Growing Supplies

Hand-picked for your Crimson Clover, with the extension research behind every recommendation.

Seed starting tray + heat mat

For gardeners who start seeds indoors, this combo improves even germination. Warm-season crops benefit from bottom heat. Look for a rigid tray, cell inserts with drainage, and a heat mat paired with a thermostat.

Source: Utah State University Extension; Iowa State University Extension; Mississippi State University Extension

Our pick

Seedling Heat Mat + Thermostat Combo

Same trusted mat with a digital thermostat so you can dial in exact soil temperature. Peppers want 80-85°F, tomatoes 75-80°F.

paid link ?When you shop on Amazon using this link, SoilStack earns a small commission at no extra cost to you. It's how we keep the site free and the calendar ad-free. Every product on this page was hand-selected based on university extension research. When you shop on Amazon using this link, SoilStack earns a small commission at no extra cost to you. It's how we keep the site free and the calendar ad-free. Every product on this page was hand-selected based on university extension research.
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Mulch / landscape fabric

Nearly every garden benefits from mulch for weed suppression, moisture conservation, and soil temperature moderation. For most home gardeners, quality organic mulch is the better buy over landscape fabric.

Source: Penn State Extension; Wisconsin Horticulture; Illinois Extension

Our pick

Cleaned Wheat Straw Mulch (3 cu ft, ~20 lbs)

Thoroughly cleaned wheat straw at 3 cubic feet, marketed specifically for vegetable gardens rather than animal bedding or decoration. Better per-pound economics than the 1 cu ft option, with the same extension-recommended material. Strong sales volume (2K+ bought past month) supports product consistency.

paid link ?When you shop on Amazon using this link, SoilStack earns a small commission at no extra cost to you. It's how we keep the site free and the calendar ad-free. Every product on this page was hand-selected based on university extension research. When you shop on Amazon using this link, SoilStack earns a small commission at no extra cost to you. It's how we keep the site free and the calendar ad-free. Every product on this page was hand-selected based on university extension research.
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Drip irrigation / soaker hose kit

Every gardener benefits from putting water at the root zone instead of on the leaves, because drip and soaker systems reduce foliar disease pressure by limiting leaf wetness and soil splash. A quality kit should include a backflow preventer, filter, pressure reducer, and UV-resistant tubing.

Source: Iowa State University Extension; Colorado State University Extension; UMass Extension

Our pick

Complete Garden Drip Irrigation Kit

Designed for beginners with a step-by-step setup guide. Adjustable emitters, both tubing sizes, and all connectors included.

paid link ?When you shop on Amazon using this link, SoilStack earns a small commission at no extra cost to you. It's how we keep the site free and the calendar ad-free. Every product on this page was hand-selected based on university extension research. When you shop on Amazon using this link, SoilStack earns a small commission at no extra cost to you. It's how we keep the site free and the calendar ad-free. Every product on this page was hand-selected based on university extension research.
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Row cover / frost blanket

Row cover adds frost protection, speeds early growth, and physically excludes insect pests without spraying. Look for spun-bonded fabric with a stated weight and frost rating, UV resistance, and enough width for hoops or low tunnels.

Source: University of Maryland Extension; University of New Hampshire Extension; Colorado State University Extension

Our pick

Frost Blanket (10'x30')

Thicker 1.2 oz fabric rated to protect down to 28°F. Covers 300 sq ft — enough for multiple raised beds in a single sheet.

paid link ?When you shop on Amazon using this link, SoilStack earns a small commission at no extra cost to you. It's how we keep the site free and the calendar ad-free. Every product on this page was hand-selected based on university extension research. When you shop on Amazon using this link, SoilStack earns a small commission at no extra cost to you. It's how we keep the site free and the calendar ad-free. Every product on this page was hand-selected based on university extension research.
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Research

Sources

Reference material and extension guidance used to build this growing guide.

reference SARE, Managing Cover Crops Profitably: Crimson Clovergovernment USDA ARS, Crimson Clover cover crop factsheet (nitrogen fixation)peer-reviewed SARE, Sustainable Agriculture Research and Education
Internal links

Crimson Clover Planting Dates by Zone

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