Crimson Clover Product Guide
By Dave Wilson, Agronomist
Note: Plant Zone Hardiness Maps – I refer to Growing Zones or USDA Plant Hardiness Zones for late summer or fall planting dates for the cover crops. After speaking with many farmers throughout the Northeast and Mid-Atlantic I’ve come to realize that many don’t know what their plant hardiness zone is. Therefore, as an appendix, the PA map of growing zones is attached.
(Trifolium incarnatum) variety ‘Dixie’
Sales locations: In the Northeast, Pennsylvania Rt. 78 and south, above this line crimson clover does not consistently over-winter, especially when we get into the zone 5a and Zone 5b areas. If snow fall occurs and stays the crimson is insulated from freezing temperatures, in open winters with no snowfall or freezing rain events the crimson clover may winter kill. The exception to this being some of the Finger Lakes region area and some other New England coastal areas that get buffered by lake or ocean effect. Otherwise the crimson is not recommended as a winter annual for these northern locations, but can be spring seeded as a summer annual.
Fall planting: seed six to eight weeks before the first killing frost.
Zone 7: August 20 – October 1 or the first opportunity in the spring.
Zone 6a: August 5 – September 10 or the first opportunity in the spring.
Zone 6b: August 10 – September 15
Zone 5: Spring plant
Zone 4: Spring plant
For spring planting as a summer annual, plant as soon as all danger of frost is past.
Note: if planted in spring or summer it will bloom in the same year and will not over winter.
Seeding rate: 15- 20 lbs/A drilled, 22 to 30 lbs/A broadcast. When planted with another crop as a companion lower the seeding rate to 10 – 15 lbs/A.
Note – Crimson clover seed should be inoculated for best performance with nitrogen fixing ‘crimson clover’ type inoculant.
Crimson Clover can be broadcast and rolled or drilled into a firm seedbed, shallow drilling produces a better stand.
There are two major types of crimson clover available commercially. The hard seeded type and the soft seeded type. The hard seeded type contains a higher percentage of hard seed that will delay germination until fall, when the conditions are favorable for growth. They are also referred to as “reseeding types” These varieties will tend to germinate in the fall if allowed to set seed in the late spring. ‘Dixie’ is a “hard-seeded” or “reseeding” variety.
When planted in the fall crimson clover will grow as a winter annual and will flower early to mid-May in the northeast.
When planted in the spring, crimson clover will grow in an annual habit flowering in the same year in 70 to 90 days.
Nitrogen: Fall planted crimson clover can fix and accumulate from 50 to 80 lbs/A of N by mid-April, this Nitrogen is primarily in the above ground growth; approximately 50% of that amount or 25 to 40 lbs Nitrogen /A is available for the following crop in the first year. If the crimson clover is left to grow until June then 140 to 260 lbs/A of N can be accumulated with approximately 70 to 130 lbs Nitrogen/A being available. Spring growing conditions will affect the growth of crimson clover and have influence on the amount of biomass and nitrogen produced.
- Use as a cover crop or green manure.
- Over-seed into small grains and other vegetable crops.
- Mix with grasses and small grains as hay or forage.
- For early season weed control and nitrogen source, crimson clover can be spring seeded, then mowed or plowed down as a green manure or sprayed and killed for a summer crop.
- Roll down at full bloom to kill or spray earlier to kill and use as nitrogen rich no-till mulch.
- Use as a cover crop for orchard systems due to its shade tolerance. It can be disked into the soil as a green manure, if reseeding varieties are used stands can re-establish every fall.
- Used as a winter cover and green manure in row crops, it can be over seeded in summer or fall crops in August or September.
- In the warmer parts of the Northeast and Mid-Atlantic Delmarva area, in a typical Soybean to corn rotation, crimson clover has been aerial seed into Soybeans before leaf drop when leaves are starting to yellow, it then grows as an overwintering cover crop and provides
nitrogen for the following corn crop in rotation.
- Crimson grows well under cool, humid conditions, quickly forming a ground cover which will compete with weeds.
- It tolerates many soil types, and can yield up to 200lbs/A of N in its biomass, although 70 to 130lb/A is more common.
- Young crimson is very palatable and seldom causes bloat. Crimson clover can be kept in a palatable vegetative state through the summer by managing it with repeated mowing, but growth is reduced in hot dry weather. It will not re-grow if grazed or mowed after flowering begins.
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