Radish (Raphanus sativus)
Technically belonging to the Chicory family, Radicchio is a quick growing bitter red leafy vegetable.
How to Grow Radish from Seed
Radishes are a moderately frost-tolerant vegetable that prefer full sun, but will tolerate partial shade. Plant in fertile, evenly moist soil that is free of rocks.
Spring radish varieties are small, fast growing (24-32 days), and become pungent and woody in the heat of summer. Direct seed spring radishes outdoors up to 6 weeks before the last frost date. For a continual harvest, sow in 1-2 week succession plantings until temperatures become hot. These radish varieties can be planted again in the fall when temperatures cool.
Winter radish varieties have larger roots and are slower to mature (60 days). Direct seed winter radishes outdoors so that they mature around the first fall frost.
Plant seed 1/2" deep and1/2-1" apart in rows 12" apart. Optimal soil temperature for germination is 55-85°F. Seeds will sprout in 4-11 days. Thin so that mature plants are 2" apart for spring radishes and 6" apart for winter radishes.
Spring radishes should be picked before they become large and woody (24-32 days). Winter radishes will be ready for harvest in approximately 60 days, depending on the variety.
How to Save Radish Seeds
An insect pollinated annual, radish can be a challenge to keep pure because in many areas there are an abundance of wild radish that will cross readily with your cultivated varieties. Being a small plant, they are easy to cage for isolation, and being fast maturing, time isolation is a great choice as well. Seed pods will form after the flowers die back, and you should allow the pods to dry on the plants for as long as possible before gathering. Pods are thick and do not shatter easily. Winnow to separate chaff.