Trifolium incarnatum Seeds | Crimson Clover
LATIN NAME: Trifolium incarnatum
COMMON NAME: Crimson Clover
Plant Profile
Crimson clover is an upright, softly hairy annual of the pea family, native to the Mediterranean basin and south-western Europe and now sown across the temperate world. It grows twenty to sixty centimetres tall, with trifoliate leaves and a conical head of crimson flowers five centimetres long, opening from April to June.
It is the earliest of the common clovers to flower, and a field of it in full bloom is one of the sights of late spring. Each head is made of many small florets, and each floret makes a single, one-seeded pod. It is shallow-rooted for a clover and does not creep or root at the nodes, so it behaves as a true annual and dies after setting seed.
Science & Biotechnology
Crimson clover is a diploid with fourteen chromosomes and, unlike most clovers, it is largely self-fertile. That matters commercially: a seed crop does not depend on a large population of bumblebees, and a field can be raised from a narrow genetic base. The flowers still attract bees in quantity, and the species is grown as much for them as for the nitrogen it fixes.
A good stand fixes seventy to a hundred and fifty kilograms of nitrogen per hectare, most of it in the top twenty centimetres of soil, which is why it is so often planted before a nitrogen-hungry crop such as maize. Part of the seed is hard-coated and will not take up water in the first autumn, germinating a year or more later; that fraction is a nuisance in a lawn and an insurance policy in a pasture.
Uses & Benefits
Its main use is as a cover crop and green manure. Sown in early autumn, it covers the ground through winter where the climate is mild, holds nitrate that would otherwise leach, and is dug in or sprayed off before it sets seed in spring. In the south-eastern United States it is the standard winter cover ahead of maize and cotton.
The flowers are cut for market, and the plant is a reliable nectar source at a season when little else is open. It makes decent hay if cut early, though the stems coarsen quickly. In cold-winter climates it is sown in spring as a one-season green manure, and it will not survive a hard frost, which is worth knowing before sowing it as a permanent pasture plant.
Growing from Seed
Sow from late summer to early autumn in mild climates, six to eight weeks before the first frost, at about twenty-five kilograms per hectare, or two grams per square metre in a garden. Broadcast onto a prepared seedbed and rake it in lightly; the seed is large for a clover and establishes from a shallow covering.
Inoculate with the clover strain of Rhizobium if the ground has not grown clover before, and roll the field afterwards to firm it. Seedlings appear in seven to ten days at 15-20 °C. In cold climates sow in early spring instead, for a summer green manure. Mow or incorporate the stand as the first flowers open, before the pods form, or it will become a weed of the following crop.
Our Take
The best early clover for a cover crop, and a fine cut flower if you let a strip bloom. Sow it in autumn and dig it in before the pods form.
Related Reading
Gardeners who grow Crimson Clover often pair it with these related subjects: