How Root Crops Grow  by National Gardening Association Editors
Root crops are cool-season vegetables. Their tiny seeds
germinate best in damp soil that's between 50&deg and 60&deg F.
Early spring and fall are the best times to plant.   Germination
is the sprouting action of seeds, and some root crops germinate
more quickly than others. Radishes sprout in just 2 to 3 days;
turnips and rutabagas in 5 to 10. The rest are slower, taking
from 7 to 20 days to germinate. When they do, tiny seedlings
push their way up through the shallow soil covering.  While the
seedling develops into the greens above the ground, a large,
edible taproot forms and grows downward. It's also the major
storage organ of the plant, although it does form smaller,
branching side roots to help it gather food, oxygen and water.
Some root crops have more of these hairlike roots than others,
but you can scrub or wash them off before eating the vegetable.
Growing On  As the root grows, it expands down, out and up;
often showing its shoulders a