Answer: The zones are determined by average coldest temperatures every winter rather than growing periods. The growing season usually means "frost-free days" which would be the time between your average last spring frost and your average first fall frost. This can vary markedly within a given winter hardiness zone, and can even vary within a small geographic area depending on microclimates. For example, a garden in a sheltered spot will have a longer season than one in a windy exposed spot or one in a frost pocket. In any case, the zones and frost dates are only averages and serve as a guide rather than a hard and fast rule. With some observation you will begin to know how closely your garden tends to follow the averages.
Days to harvest is the average time from either planting the seed in the garden or setting out the transplant into the garden. In most cases this is not of particular concern because there is plenty of time for things to ripen. In other cases, for plants needing a warm soil and warm sunny days such as tomatoes or melons, it is a good idea to look for the shorter season varieties -- the types with a shorter days to harvest. It is also of concern if you plan to do intensive gardening where you use the same square footage to grow several crops in succession during the season. Your County Extension (788-8450) should be able to suggest varieties which do particularly well in your area and provide you with the average frost dates as well.
Finally, the "Easter Egg" radishes are quite edible assuming you like radishes.
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