When to Plant Radish: Sow Every Two Weeks for a Long Harvest

The year at a glance

Spring and fall are the main radish seasons; summer and winter take extra effort. Rather than filling a whole bed, sow a little at a time in the gaps between other crops. That suits a home garden best.

The table below is a general guide for a temperate garden. In mild-winter areas the fall window runs a couple of weeks longer, and in cold areas spring starts a couple of weeks later. Elevation and distance from the coast shift things by another week, so treat it as a starting point.

Spring is a race against pests

As spring warms up, flea beetles and aphids multiply. When radish leaves are eaten the roots stop growing too, so the surest approach is to put insect netting over the bed the day you sow.

Mid-spring sowings are ready in about 20 days. Leave them into early summer and heat and heavy rain will split them, so plan to finish sowing by late spring.

1. Net the bed on sowing day Set up hoops and cover them with fine insect netting, weighting the edges with soil. By the time seedlings are up, the beetles have already arrived.
2. Sow every two weeks Work along the bed a little at a time. A dated label at each sowing tells you when to start checking.
3. Finish sowing by late spring Sowings that run into early summer meet heat and pests and fail more often. Decide your last sowing date in advance.

In summer, shade them and grow only a few

In high summer they mature faster but tend to make leaves instead of roots. It can be done: lower the light and soil temperature with shade cloth and keep it to a couple of short rows.

Running dry is the biggest danger in summer. Water deeply once in the morning, and check again in the evening on days they wilt. Let them dry out and then water and they will split every time.

Germination is quick in summer, often two days. The trouble comes after: with hot soil day after day, the leaves grow while the roots never swell. A straw mulch to cool the soil helps somewhat.

1. Put up shade cloth Shade cloth that cuts about 30 percent of the light lowers soil temperature. It can stay on all the way to harvest.
2. Water in the morning Water deeply before the sun is high. Watering in the heat of the day swings the soil temperature and stresses the roots.

Summer radishes tend to be hot. Pulled small, they are milder and easier to eat raw.

Fall is the easiest season

From late summer into fall the weather cools, pests fade and the roots fill slowly and firmly. Shape and flavor are at their best, so this is the sowing to choose for a first try. Three sowings two weeks apart carry you into late fall.

As fall goes on, days to harvest stretch from 30 to 40 or more. Cover the last sowings with row cover to keep them warm and you can still pull them before the hard frosts.

Tuck them into gaps in the garden

Radishes are done in three to four weeks, so they fit between other crops: the gap before summer crops go in, or the gap before fall and winter crops are planted.

You can also sow between rows of widely spaced crops. While tomato or eggplant plants are still small the radishes get sun, and by the time they are pulled the main crop is ready to take over the space.

1. Use the gap before planting If you have at least 30 days before the next crop goes in, that bed can take a sowing. Set a date to clear it so planting is not delayed.
2. Sow between larger crops Sow between rows of crops that will grow big. The condition is to harvest before they shade the radishes out.
3. Rotate away from cabbage family crops Do not follow other cabbage family crops like turnips, mustard or cabbage. It invites clubroot, so leave two years before returning.

Winter, and adjusting for your area

In the depth of winter, radishes barely grow outdoors. You can grow them under a low tunnel or in a bright cold frame, but it can take 60 days or more. In most gardens, waiting for spring is a better use of effort.

Even within one region, a coastal garden and an inland one can be a week apart. Note the sowing date and first harvest date each time, and from the next year on you can plan with your own garden's numbers.

If you do grow them in winter, a double layer of cover raises the daytime temperature. On sunny days it gets humid inside, though, so you will need to open the ends for air. Whether that is worth it depends on what else you are growing.