~ CIRCULAR 137, U. S. DEPARTMENT OF AGRICULTURE 
although C. retusa and C. spectabilis are more or less exceptions to 
this rule, as they mature at one particular time a large percentage of 
the seed produced during the season. 
CLIMATIC REQUIREMENTS 
Most of the species of Crotalaria are tropical or subtropical in 
their requirements, and in the continental United States they are 
treated mostly as summer annuals. One native perennial species 
(C. rotundifolia (Walt.) Poir.) is found as far north as southern 
Virginia, while a native annual species (C. sagittalis L.) extends as 
far north as the New England States. 
In experimental work with a number of species in Mississippi, 
Georgia, South Carolina, and Florida a temperature of 28° F. has 
been the minimum the growing plants will stand without damage. 
While the adaptation and limitations of the various species have 
not been determined, limited experiments indicate that some species 
can be grown farther north than others. Of the two species tested 
somewhat extensively, (. spectabilis seems to be suited to conditions 
farther north than C. striata. At the Arlington Experiment Farm, 
Rosslyn, Va., C. spectabilis planted May 20, 1929, was in full bloom 
September 20, and had attained a height of 3 feet. C. striata dur- 
ing the same period made a growth of 8 to 10 inches with no bloom. 
At Gainesville, Fla., C. anagyroides is the only species tested that 
has perennated to any extent under field conditions. In a few cases 
when the winters have been exceptionally mild or the plants were 
growing in protected locations, the plants of C. striata, C. usaramoen- 
sis, and C’. incana L. survived the winter. 
SOIL AND MOISTURE REQUIREMENTS 
The work with Crotalaria species has not been extensive enough 
to determine definitely their limitations with reference to soil and | 
moisture requirements. It is known, however, that they vary some- 
what in this respect. While many species are native in tropical 
regions of heavy rainfall, none, so far as known, is adapted to wet 
situations. A well-drained soil is essential to good growth. The 
species that have been under experimental trial have indicated their 
ability to stand through droughty periods, and a few species are 
known which grow under extreme desert conditions. 
In general most species of Crotalaria are adapted to sandy or light 
loam soils. Whether or not there may be species adapted to heavy 
clay soils is not known. Experimental work on heavy soils to date 
has indicated that the species tested are not well adapted to such soil. 
A few plantings on clay-loam soils have given fairly good results. 
On poor sandy lands in the South several species have made a 
large growth in comparison with other legumes, and it is for such 
situations that they are attracting special attention. 
PALATABILITY TO LIVESTOCK 
Many species of Crotalaria have a bitter taste in the green state 
and seem to be avoided by livestock. C. striata and C. spectabilis 
are included in this group. The latter is less bitter than the former. 
