The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
-" Agronomy Research Report AY 78-2 October 1977
Department of Agronomy
University of Florida '" L
Gainesville, Florida 32611
9 SUBTERRANEAN CLOVER
G. M. Prine1 Of- Florid
Subterranean clover (Trifolium subterranean L.) is a new crop to
Florida and the South, even though it has been grown at Experiment Stations
periodically over the last half century. Subterranean clover is widely
grown along the west coast of USA, particularly California, where Mediter-
ranean climates (hot, dry summers, and cool, wet winters) occur. Following
promising recent research results in Mississippi, seed companies are begin-
ning to import and sell subterranean clover seed in the Southeast. This
availability of seed prompted the writing of this report, though research
results with subterranean clover in Florida are still very limited.
Subterranean clover (sub clover) is seeded on over 60 million acres in
Australia. Sub clover is best adapted to Mediterranean climates where it
germinates in the fall and matures in the spring. In Florida we have the
mild winter temperatures and usually have adequate winter rainfall needed
for growing sub clover. However, rainfall may be low and undependable
during the fall establishment period (late September, October and early
November). Our heavy summer rainfall does not affect the growth of sub
clover plants but can affect reseeding. The dormancy and hardness of sub
clover seed is often not as great during summer as some of our other re-
seeding annual clovers, such as crimson and arrowleaf clovers. Conse-
quently the.seeds of sub clover sometimes germinate during summer and
seedlings die before cool weather. However, Mount Barker and Woogenellup
sub clover seed have both reseeded well in the fall at Gainesville. It is
probable that some of the other sub clovers will reseed equally well but we
do not have satisfactory data yet on other cultivars.
The growth of sub clover is prostrate with stems growing close to soil
and leaves forming a dense canopy. In fact, over one-half of foliage dry
Professor of New Crops and Plant Introductions, Department of
Agronomy, Gainesville, Florida 32611.
matter may be produced in the first two inches above soil. For this reason
sub clover is used mainly for grazing. If grown in a mixture with a grass
such as ryegrass, sub clover will develop erect growth that can be har-
vested as hay. However, in Florida it is suggested that if you are pri-
marily interested in producing hay that you should plant a taller growing
clover, such as red, crimson or arrowleaf clover.
The life cycle of sub clover is quite similar to that of crimson
clover. When soil moisture is available the late maturing cultivars may
grow from late September or early October until about the first of May. In
Australia where sub clover is mainly grazed by sheep, the dead foliage and
seed pods furnish feed during their long dry summers. In Florida, the dead
foliage breaks down rapidly during the humid, rainy summers, releasing ni-
trogen to summer grasses.
Sub clover gets its name from the fact that the seeds are produced in
burs below soil surface. However, seed burs of some cultivars may be
mainly produced on the soil surface. Flowers are small and inconspicuous
and are often hidden from view in the foliage. Sub clover forage has high
quality and compares favorably with that of other clovers.
In Mississippi, where much of the recent sub clover research has been
conducted, they have found that the later-maturing cultivars in general are
most productive. Mt. Barker, Woogenellup and Tallarook have generally been
the highest yielding cultivars. Preliminary trials in Florida indicate
these cultivars to be the best or among the best commercial cultivars for
Florida (See Table 1.).
SUB CLOVER PLANTING RECOMMENDATIONS
Soils: Sub clover should be grown on soils with good drainage and is
not recommended for flatwoods or other poorly-drained soils. White and red
clovers should be grown on these latter soils.
Seeding rate: 16 to 20 pounds per acre in pure stand, 8 to 10 pounds
per acre if in mixture with small grains, ryegrass or other clovers.
Seeding depth: Varies with soil type from about 3/8 to 1/2 inch on
clay soil to about 1 inch on sands.
Time for seeding: Seed on prepared seedbed anytime in October that
soil moisture is favorable and minimum temperatures have dipped below
600 F. Seeding into perennial grass sods should wait until late October or
early November when grass growth is reduced by night temperatures below
500 F. Seeding should follow rainfall which has wet soil surface to at
least 6 inches depth.
Liming and fertilization: Similar to other cool season clovers. Soils
should be limed to pH of 6.0 to 6.5 and have CaO content of at least 900
pounds per acre. Fertilize according to soil test recommendation or apply
300 to 500 pounds per acre of 0-10-20 or 0-10-30 fertilizer at planting. In
extremely sandy soils apply 300 pounds per acre of the above fertilizer at
planting and 200-300 pounds per acre in late December or January. The
fertilizer should also furnish sulfur at rate of 20 to 30 pounds per acre
per season. Minor elements are needed on soils where they are deficient.
Inoculation: Use a commercial inoculant specifically made for sub
clover at 2 to 5 times the recommended rate on packages. The PELINOC
system developed by the Nitragin Company has worked well for us but other
sticker coatings may work just as well. If the seed has been preinoculated,
be on the safe side and inoculate the seed again at planting. If you fail
in getting good inoculation, sub clover will give very unsatisfactory
Grazing: Sub clover can be closely grazed even during seed production.
Sub clover, or any clover, must have enough leaf surface to adequately
absorb sun light and fix an optimum amount of this energy as plant food. If
you can readily see soil surface and horizonal stems where you have good
stands of sub clover you are probably over-grazing. Sub clover is usually
ready for grazing soon after it begins to develop full-sized leaves instead
of the smaller juvenile leaves. Under good conditions the sub clover plants
should continue to grow these large leaves until after start of flowering
when leaves become smaller, especially near tip of stems.
Reseeding: At present sub clover should be looked on primarily as a
reseeding winter annual on perennial grass sods. The production of seed
under close grazing and the large seed which produce a large vigorous seed-
ling are sub clover's biggest advantages over other annual clovers.
Cultivars: We have tested Tallarook, Mt. Barker.and Woogenellup cul-
tivars enough to know that they yield well. Mt. Barker and Woogenellup have
both reseeded better than Tallarook in our preliminary trials. Other cul-
tivars may be just as good but have not been tested enough to draw con-
clusions yet. In Australia, seed of several sub clover cultivars are often
mixed together for seeding.
Cold damage: Sub clovers will live through freezes normally expected
for Florida though they may sometimes be damaged. On basis of notes taken
following the January 18, 19, and 20, 1977 freeze (Table 1), it is suggested
that Clare, Seaton Park, Dinninup and Yarloop cultivars not be seeded alone
as they suffered more severe damage than other sub clover cultivars.
Adaptation. The further south sub clover is grown in Florida, the
shorter is the life cycle and the lower is the forage yield. It is unlikely
that sub clover will produce enough forage to merit seeding south of the
28th parallel which goes across the state at Tampa. Best sub clover growth
is expected in North Florida above the 30th parallel which crosses the
Peninsula south of Lake City.
Seed dealers should be able to obtain sub clover seed through their
suppliers. In case they cannot, below is a list of seed distributors known
to have sub clover seed at the writing of this report.
1. Australian Pasture Seeds Inc.
5359 Leake Avenue
New Orleans, LA 50115
2. Northurp, King and Company
P. O. Box 12123
Fresno, California 93776
3. Sawan Seed Company
Table 1. The dry matter yield of sub clover cultivars grown on well-drained soil (Arredondo fine
sand) at Gainesville during two growing seasons.
Sub clover 1975-76 season 1976-77 season
cultivars forage yield Forage yield Freeze damage**
Mr. Barker 2750 (4880)* 2550 2.8
Woogenellup 2260 (4010)* 2740 2.8
Tallarook 2260 (5720)* 2540 2.0
Clare 1290 8.4
Dinninup 1240 7.3
Dwalganup 1840 2.7
Howard 2390 2.3
Miss. Ecotype 1760 1.0
Nangeela 1710 1.0
Geraldton 1090 2.0
Seaton Park 1420 8.3
Yarloop 1360 5.3
* Numbers in parenthesis are yield of forage when sub clover top growth was cut to soil surface at the
last harvest. Other yield values were harvested at 1 inch height above soil. The latter method
of harvesting cuts off very few of the horizonal stems so the forage yield is mainly leaves and leaf
**Freeze damage ratings were made following the severe freeze of January 18, 19 and 20, 1977 when min-
imum temperatures were 200 F or less each morning. Rating: 0 = no damage to 10 = all top growth
killed. All damaged sub clover eventually recovered.