Guar, also called cluster bean because of the manner in which its pods are clustered together, was formerly referred to as C. psoralioides.
Guar is a native plant of India, where it is grown principally for its green fodder and for the pods that are used for food and feed. It has soil-enriching properties since it is a legume. According to the American Society of Agronomy, the primary importance of guar is the commercial value of its seed gum (galactomannan gum). This gum has a wide variety of food and non-food uses.
Guar was introduced into the United States from India in 1903. Production in the United States is centered in Texas, Oklahoma, and Arizona, but it is also adapted to locations with more tropical climates, such as in Florida and Puerto Rico. However, very little information is available on the use of this crop in Florida.
Guar is a coarse, upright, bushy, drought-resistant summer annual, ranging from 2–9 feet in height. It has pointed, saw-toothed, trifoliate leaves, small purplish flowers borne along the axis of a spikelet, and hairy pods 3–4 inches long in clusters. There are both dwarf and tall cultivars.
Guar flowers are self-pollinating. A mature unopened bud starts out white and then changes to a light pink as petals begin to open. Finally, the flower is deep blue.
Guar is sensitive to cold, so should be grown during the warm season. A soil temperature of 70°F is necessary for seed germination. Guar has an indeterminate growth habit, growing both vegetatively and setting pods from about 4–6 weeks following seedling emergence until death of the plant due to cold or annual decline. Guar is a short-day plant, setting more dense clusters in winter (in Puerto Rico) than in summer. Although the plant is reported to be fairly drought resistant, it grows even better when irrigated. Drought during the prolonged fruiting period reduces yields.
The culture of guar (spacing and method of seeding), is similar to that for soybean. If grown in the garden, which seldom is the case, it should be grown much like the cowpea (Southern pea).
In South Florida, try planting guar during the period September through February so that the fruiting period coincides more or less with the shorter day lengths of the year. Where there is danger from killing frosts, as in the central and more northern areas of the state, plant a spring crop or a fall crop. These cultural suggestions are for guar grown as a vegetable plant and should not be considered for its production as an agronomic crop.
For use as a vegetable, pods must be picked when young, before they become hairy and woody. They are eaten most often as a French bean or as a curry vegetable.