Planting
As with other root crops, radish varieties can only
be properly maintained for trueness to type if they
are grown using the “root-to-seed method” which
allows for selection of the roots before seed
production begins. The radish roots, or
“stecklings”, are first produced by planting the
seed in a “root nursery” in much the same way
that a commercial radish vegetable crop is grown.
With this method, roots are then pulled from the
ground at edible maturity, selected based on root
morphological characteristics (appearance) and
then replanted (see picture below) in a different
field at a wider inter- and intra-row spacing to
provide adequate space for the subsequent
reproductive stages that lead to a seed crop. It is
best to avoid planting before the occurrence of
environmental conditions that support vigorous
root growth, thereby avoiding “growth checking”
which may alter the appearance of the roots.
Alternately, using the “seed-to-seed method”
doesn’t require pulling the crop and replanting.
Simply plant the crop sparsely in the row and thin
back the rows to an appropriate seed production
spacing (see Spacing). This method should only
be used if the grower knows that the seed lot that
they are starting with is of excellent genetic
standing with a high degree of uniformity in all of
the important phenotypic characteristics. It can
take as few as two to three consecutive seed to
seed generations for some varieties to become
irregular and non-uniform.