Height frequently doubles after the first flowers appear. However, some varieties developed for double cropping in southern Missouri are of this growth type and merit consideration due to their ability to grow taller than determinate varieties in a short growing season. The determinate semi-dwarfs are true determinate varieties but are about half the height of normal varieties. Semi-determinate varieties are 6 to 10 inches shorter than common varieties and add only a small amount of vegetative growth after flowering and podding begin. Flowering periods of both types are slightly shorter than in commonly grown varieties.
Most varieties are pure line, but a few are a blend of two or more pure varieties.
In general, blends perform no better than pure varieties. With the exception of yield, which reflects the total response of a variety to a set of growing conditions, maturity is the most important criterion in selecting a variety. If a variety is too early or too late at a location, it will be limited in potential performance. Soybean varieties are classified into 13 maturity groups, from Group 000 grown in Canada to Group X grown in the tropics. The earliest and latest varieties within a group may differ by as much as two weeks in maturity.