Produced by Tom Cosmas from files generously made available
by USDA through The Internet Archive. All resultant
materials are placed in the Public Domain.

Transcriber Note

Emphasis is denoted as _Italics_ and =Bold=.

=CRIMSON CLOVER=

LEAFLET No. 160

U.S.DEPARTMENT of AGRICULTURE

  Issued June 1938.
  Revised January 1947

=CRIMSON CLOVER=

By E. A. Hollowell, senior agronomist, Division of Forage Crops and
Diseases, Bureau of Plant Industry, Soils, and Agricultural Engineering,
Agricultural Research Administration

=Contents=

                                        Page
  Adaptation                               3
  Seedbed Preparation                      3
  Fertilizers                              3
  Seed Sources and Varieties               4
  Dixie Crimson Clover                     4
  Rate and Time of Seeding                 5
  Inoculation                              5
  Unhulled Seed                            5
  Companion Crops                          6
  Diseases and Insects                     6
  Utilization                              6
  Seed Production                          7

[Illustration: Figure 1.--Principal crimson clover regions of the
United States. The dotted area shows where crimson clover was generally
grown before 1938. The cross-hatched area shows where production can be
extended by using favorable cultural and fertilizer treatments and adapted
varieties.]

CRIMSON clover (_Trifolium incarnatum_) is the most important winter
annual legume of the central section of the Eastern States. This crop can
be grown over a much larger area by using seed of adapted varieties for
each section, by using better cultural methods, and by fertilizing the
soil (fig. 1). Besides being an excellent pasture plant and furnishing
plenty of hay, it protects the soil during fall, winter, and spring,
prevents soil washing, and provides green manure for soil improvement.
This legume has the distinct advantage of producing large quantities of
seed that can be easily harvested and sown without the use of expensive
machinery. Crimson clover is a native of Europe and is widely grown in
France, Hungary, and other central and southern European countries. Seed
was introduced into this country as early as 1819, but it was not until
1880 that the plant became important. The acreage has been steadily
increasing. During the 5-year period 1940-45 the annual purchase of seed
through markets in the United States has ranged from 6 to 18 million
pounds. In 1935 about 2 million pounds were used. In addition, large
quantities of home-grown seed are handled from farm to farm.

The common name of this clover is derived from the bright crimson color of
the blossoms. Other such common names as German clover and scarlet clover
are frequently used. In general the leaves and stems resemble those of red
clover, but are distinguished by the rounded tips of the leaves and more
hair on both leaves and stems. When crimson clover is planted in fall the
leaves develop from the crown and form a rosette, which enlarges whenever
weather conditions are favorable. In spring, flower stems develop rapidly
and end their growth with long pointed flower heads. Seed forms and the
plant dies with the coming of hot summer weather. The seed is yellow and
is about twice as large as red clover seed and more rounded.

=Adaptation=

Crimson clover does well in cool, humid weather and is tolerant of winter
conditions where the temperature does not become severe or too changeable.
It may be planted from midsummer to late fall. In the northern part of the
region early seeding and growth are necessary for the seedlings to survive
the winter. It will thrive both on sandy and clay soils and is tolerant of
ordinary soil acidity. On very poor soils, stands are difficult to obtain
and the growth is stunted. The use of phosphate and potash fertilizers and
manure on such soils will help to obtain good stands.

Crimson clover may also be grown successfully as a summer annual in
northern Maine, Michigan, and Minnesota. Winter culture can be extended
into Kentucky, southern Missouri, southern Indiana, and Ohio, provided
varieties are grown that are adapted to these sections and the seed is
sown in fertile soils early in August.

=Seedbed Preparation=

The most important and difficult part of producing a large crop is getting
a stand. Enough soil moisture to sprout the seed and establish the
seedlings is the greatest factor in obtaining a stand. When established,
common crimson clover usually produces a good crop.

Seedings may be made alone or combined with winter grains, ryegrass, or
grass sod. It is possible also to seed between the rows of cultivated
crops, but it is difficult to make an ideal seedbed. Furthermore, the crop
plants in the row shade the clover seedlings and use some of the available
moisture. If the row crop is planted in wider rows and seeded more thinly,
the clover will become better established. When planted between the rows
of other crops, the seed is usually broadcast on the surface and covered
by cultivating or harrowing. Drilling the seed after the soil surface has
been stirred usually gives more complete stands than broadcasting, and it
may be done with a small one-horse drill. The seed should not be planted
more than one-half to three-fourths of an inch deep, respectively, in clay
and sandy soils.

Crimson clover is often seeded following a grain crop. This is a surer
method of establishing a stand than planting between the rows of
cultivated crops, provided the seedbed is well prepared. After the grain
crop is harvested the soil is plowed or disked and allowed to settle.
This is followed by light harrowing or disking to kill weed seedlings.
Before the clover is seeded the sod should be firmly packed, because a
loose cloddy seedbed will not produce good stands. The seed may be either
drilled or broadcast, but drilling will give more uniform stands.

=Fertilizers=

Good stands and growth cannot be expected on very poor soils. Soil
conditions can be improved by adding phosphate and potash fertilizers and
manure or by turning under such crops as cowpeas, soybeans, or lespedeza.
In many soils of low fertility the use of a complete fertilizer will
encourage early seedling growth and establishment. On fertile sods crimson
clover may be successfully grown without fertilizer, but on most sods
applications of 200 to 400 pounds per acre of phosphate and 50 to 100
pounds of potash pay in obtaining good stands and vigorous growth (fig. 2).

[Illustration: Figure 2.--Effect of phosphate application on good soil:
Treated (left); untreated (right).]

Frequently a single large application of phosphate and potash fertilizer
is sufficient to produce two crops of crimson clover before it becomes
necessary to make another application. In some soils the addition of such
minor elements as boron may improve growth and increase seed yields. Since
the need for minor elements varies from place to place, their use should
be based on the recommendations of the agricultural experiment station of
the State in which the clover is planted.

=Seed Sources and Varieties=

Before World War II more than half the crimson clover seed used in the
United States was imported, principally from Hungary and France. Since
1938 domestic production has rapidly increased, reaching more than 18
million pounds in 1942. Tennessee produced more than half the home supply.
Nearly all the crimson clover may be called common crimson clover, since
it does not represent strains or varieties having special characteristics.
White-flower strains and several others that differ slightly in maturity
have been selected but have not been used.

=Dixie Crimson Clover=

Dixie crimson clover is a new hard-seeded variety that has given promising
results in extensive trials. It is more widely adapted than common crimson
clover, as it grows well in the Gulf coast section and appears to be
slightly more winter-hardy than common crimson. Dixie has successfully
volunteered to good stands when grown in pastures with Bermuda grass, with
small grains for grazing, and in rotation with such cultivated crops as
sorghum or late-planted corn.

Seed of Dixie shattered in harvesting operations has successfully produced
good volunteer stands in fall. When used in rotations with cultivated
crops, the seed must be matured before the seedbed is prepared for the
following crop. When Dixie is used in pasture, care should be taken to
prevent close grazing at the time of blooming, since it may limit the
quantity of seed produced and cause thin fall stands. Summer-growing
grasses must be either closely grazed or clipped in fall to give the
clover seedlings a chance to become established.

The seed and plants of Dixie cannot be distinguished from common
crimson clover, and the variety may be readily contaminated by either
cross-pollination or mechanical mixtures. For these reasons the farmer
buying Dixie should buy only certified seed.

=Rate and Time of Seeding=

Under ordinary conditions 12 to 15 pounds of hulled seed to the acre will
give good stands unless there is lack of soil moisture. Depending upon the
quantity of chaff and pieces of stems, 45 to 60 pounds of unhulled seed
is comparable with 15 pounds of hulled seed. Crimson clover may be sown
from the middle of July until November, depending upon the location, with
the expectation of obtaining a good stand. The later it is seeded the less
growth can be expected and the more readily winterkilling occurs. Early
establishment becomes more important as plantings are extended northward.
Seeding crimson clover either immediately before or following heavy rains,
if possible, increases its chances of making a stand. Spring planting
in or south of the Corn Belt usually results in a short, stunted growth
followed by little blossoming and low yield.

=Inoculation=

In many areas where crimson clover has been grown successfully for several
years it is not necessary to inoculate the seed with bacterial cultures
for the production of nodules. But either the seed or the soil must be
inoculated if crimson clover has not been grown. If the plants are not
inoculated they will develop slowly, become yellow, and die. Inoculated
plants are able to obtain about two-thirds of then nitrogen from the air
through then root nodules. The plants may be artificially inoculated by
applying cultures of the bacteria to the seed or by scattering soil from a
field where inoculated crimson clover has been grown. Two hundred to three
hundred pounds per acre of such soil evenly distributed at seeding time is
usually sufficient.

When crimson clover is grown for the first time an additional inoculation
treatment is recommended if weather conditions are dry and hot after
seeding. This supplemental inoculation consists in mixing commercial
cultures with sand, soil, or cottonseed meal and broadcasting the
mixture over the soil surface during cloudy, rainy weather as the young
seedlings are emerging. A bushel-size culture mixed with 60 pounds of the
above-mentioned material is sufficient for an acre if distributed evenly.
Soil from a field where inoculated crimson clover has been grown may also
be used for the supplemental treatment.

=Unhulled Seed=

Using unhulled common seed increases the chance of obtaining thick stands.
When the soil is dry, light rainfall does not cause the unhulled seed to
sprout, but hulled seed germinates readily and the seedlings may die from
lack of moisture before they can become established.

Its bulky nature makes unhulled seed more difficult to distribute
uniformly than hulled seed. It must be broadcast and may be harrowed in.
It is also difficult to market and is not generally handled by the seed
trade. But farmers can harvest seed for their own use and save the expense
of having it hulled.

=Companion Crops=

Rye, vetch, ryegrass, and fall-sown grain crops are often seeded with
crimson clover. Such crops are seeded at half to a third the normal rate,
and the crimson clover is seeded at half to two-thirds the normal rate.
Seeding is done at the same time, but, as a greater depth is required
for most of the seed of the companion crops, two seeding operations are
necessary.

Farmers often use a mixture of 5 pounds of red clover and 10 pounds of
crimson clover per acre with excellent results. The first growth of the
mixture may be grazed or harvested for hay or for crimson clover seed,
while the second crop is wholly red clover. Dixie crimson clover has given
good results when planted with Johnson and Bermuda grasses.

=Diseases and Insects=

The most serious disease that affects crimson clover is crown rot. The
effect of this disease is seen early in spring and is characterized by
the plants dying in patches. The stems rot at the surface of the soil or
where they join the crown. Continued damp, cool weather during winter and
early spring favors the development of the disease. This disease can be
controlled by not growing clover or other legumes in rotation for 2 to 5
years.

Sandy soils in the southern part of the crimson clover belt are often
infested with nematodes. Nematode injury stunts and yellows the plants.
While the clover-seed chalcid, the pea aphid, and other insects sometimes
become numerous in crimson clover, insects do not ordinarily cause
appreciable damage.

=Utilization=

Crimson clover grows rapidly in fall and spring and furnishes an abundance
of grazing (fig. 3). If planted early and good fall growth is made,
the clover may also be grazed during the fall and winter months. Such
a practice has been successfully followed in many States where crimson
clover is providing winter pasture. Crimson clover combined with small
grains or ryegrass has been most widely used for winter grazing. Crimson
clover makes little growth during cold periods in winter. Under such
conditions, to prevent close grazing, it is necessary to remove the
animals or shift them to other fields that have not been grazed.

[Illustration: Figure 3.--Crimson clover provides an abundance of early
spring grazing.]

Animals grazing on crimson clover seldom bloat; however, it is advisable
not to turn them into clover fields for the first time when they are
hungry. Bloat is less likely to occur on a mixture of clover and grass
or grain then when the clover alone is grazed. As crimson clover reaches
maturity the hairs of the heads and stems become hard and tough. When
it is grazed continuously or when it is fed as hay at this stage large
masses of the hairs are liable to form into hair balls in stomachs of
horses and mules, occasionally with fatal results. If small quantities of
other feeds, particularly roughages, are fed along with the clover, the
formation of these balls will be reduced. Cattle, sheep, and swine do not
seem to be affected.

Crimson clover makes excellent hay when cut at the early-bloom stage,
although the yield may be slightly reduced. For best yields it should be
harvested in full bloom. The hay is easily cured either in the swath or in
the windrow. Fewer leaves are lost and less bleaching occurs in windrowed
hay. Although yields as high as 2½ tons per acre are not uncommon on
fertile soil, 1½ to 2 tons is the usual harvest.

Crimson clover is an ideal green-manure crop. For best results it should
be plowed under 2 to 3 weeks before the succeeding crop is planted. This
gives enough time for decomposition, which is rapid unless the crop is
ripe when turned under. Occasionally strips are plowed in which row
crops are to be planted, allowing the clover between the plowed strips
to mature. Seed may be harvested by hand from the clover between the row
crops, and the remaining clover straw allowed to mat and serve as a mulch,
or the entire plant may be permitted to form a mulch.

Crimson clover may be made into silage by the same methods as are used
for other legumes and grasses. In orchards it is often allowed to mature,
after which it is disked into the soil. A volunteer stand from shattered
seed may be obtained in fall by using the Dixie variety.

=Seed Production=

Crimson clover is a heavy seed-producing plant, and yields of 5 to 10
bushels per acre are common, depending upon the thickness of the stand,
the extent of growth produced, and the care used in harvesting the seed.
The florets are self-fertile, but bees increase the number of seed
per head by tripping and transferring the pollen. Placing colonies of
honeybees next to blooming fields will increase pollination. More seed is
usually produced on soils of medium fertility than on rich soils, since
fertile soils seem to stimulate the growth of stems and leaves rather than
develop flower heads.

Large yields and ease of harvesting seed are two important reasons why
crimson clover is such an ideal legume crop. Farmers can save seed with
very little expense other than their own labor. When the seed heads are
mature they readily shatter and are easily harvested either by hand
stripping or by using horse-drawn home-made strippers. One bushel of
unhulled seed contains about 2 pounds of hulled seed, and although bulky,
it can be easily stored on the farm until fall.

[Illustration: Figure 4.--Crimson clover seed crop cut with a mower
equipped with a bunching attachment.]

When the seed is mature the crop is cut with a mower (fig. 4), which
may be equipped with a bunching or windrowing attachment, or it can be
harvested with a combine. During wet seasons it is sometimes difficult
to combine the seed from standing plants. Under such conditions the
plants can be cut and windrowed and than threshed by the combine from
the windrow. As crimson clover shatters easily when ripe, cutting with
the mower when the heads are damp with dew or rain is recommended. If it
is allowed to stand too long after ripening a beating rain will shatter
much of the seed. After a few days of curing, the seed is hulled with
an ordinary clover huller, with a grain separator equipped with hulling
attachments, or by a combine equipped with pick-up attachments or used
as a stationary machine. The less the clover is handled the less seed
will be lost by shattering. Many troublesome weeds are difficult to
separate from crimson clover seed, including field peppergrass (_Lepidium
campestre_), wintercress (_Barbarea praecox_), and the bulblets of
wild onion (_Allium_ spp.), which are probably the worst. Seed of the
mustards, rapes, and turnips (_Brassica_ spp.), dock (_Rumex crispus_),
wild geranium (_Geranium dissectum_), sorrel (_Rumex acetosella_), and
catchweed (_Galium aparine_) are also found in the seed. Little barley
(_Hordeum pusillum_) is a pest in unhulled seed, and the use of such seed
will naturally increase the prevalence of this weed.

                  U. S. GOVERNMENT PRINTING OFFICE: 1947

               For sale by the Superintendent of Documents,
                     U. S. Government Printing Office
                  Washington 25, D. C. -- Price 5 cents

=Transcriber Note=

Illustrations moved to avoid splitting paragraphs and closer to references
in the text. Minor typos may have been corrected. Table of Contents added
to facilitate searching for topics.