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Long white radishes go in during spring once the soil warms, and again in early fall. Summer brings bolting and the worst insect pressure, and winter stops growth, so both are rest periods. The calendar matches the round red radish, but the long white type does its best work in fall, when the roots grow straighter and sweeter. Adjust by two to four weeks later in cold regions and two weeks earlier in warm ones.
| Season | Tasks | What the plants are doing |
|---|---|---|
| Midwinter | Rest | Rest the bed; decide where spring radishes go |
| Late winter | Prepare the soil | Lime and deep-dig as soon as the ground can be worked |
| Early spring | Start sowing | Soil above 50 F (10 C); floating row cover on |
| Mid spring | Sow, thin | First sowings leaf out; pests begin to appear |
| Late spring | Last sowing, harvest | Harvest earlier sowings; bolting risk rises |
| Early summer | Harvest, clear | Pull the last spring roots promptly |
| Midsummer | Rest | Too hot and buggy for long radishes |
| Late summer | Fall soil prep | Deep-dig, remove stones, lime |
| Early fall | Main sowing | Netting on from day one |
| Mid fall | Last sowing, thinning | Earlier sowings start to yield; latest sowing is thinned |
| Late fall | Harvest | Early-fall sowings mature; finish before hard frost |
| Early winter | Clean up | Clear the bed, take netting off, rest the soil |
Days from sowing to harvest run 25 to 30 in spring, about 30 for an early-fall sowing, and 40 to 55 for a mid-fall sowing. The cooler it gets, the longer it takes.
Spring: fast, but a race against bolting and bugs
Spring crops grow into rising warmth and finish quickly; sown as soon as the soil warms, they are ready in about four weeks. But as days lengthen the plants bolt before the root fills, and flea beetles and cabbage worms build through mid spring, so spring sowings must be netted.
- Sow under row cover as soon as soil passes 50 F (10 C) Cold soil gives ragged germination. Lay floating row cover after sowing for warmth, and switch to insect netting once the seed leaves open.
- Sow a row every two weeks through mid spring Two or three staggered sowings two weeks apart keep radishes coming for six weeks. Sowing everything at once means everything is overgrown at once.
- Stop sowing by late spring Sowings after late spring bolt and get chewed before the root fills. Make your last spring sowing before the days get long and hot.
Fall is the easiest season
Sown in early fall, the plants grow into cooling weather, the roots fill slowly and evenly, and the flavor is mild and sweet. Insects are still around at the start of fall but thin out as nights cool. For long white radishes this is the main crop, when the straight white roots come out cleanest.
- Prepare the bed in late summer While it is still warm, dig 6 to 8 in (15 to 20 cm), remove stones, work in lime and wait two weeks. Add compost and base fertilizer a week before sowing.
- Sow every two weeks through early fall Three sowings two weeks apart from early fall give a steady harvest from mid fall until frost.
- Early fall is the last sowing date Even in a mild climate, a sowing much later than early fall matures into frost. Make early fall your cutoff, or plan on row cover.
Week by week for an early-fall sowing
Here is how a crop sown in early fall in a mild climate typically runs. Because it grows into cooling weather, everything takes one to two weeks longer than in spring, and growth slows noticeably once daytime highs sit in the low 60s F (around 16 to 18 C). Go by the plant's stage and the look of the shoulders rather than the date.
| Week | What the plants look like | What to do |
|---|---|---|
| Week 1 | Seed leaves in three to five days | Check under the net; water when dry |
| Week 2 | One or two true leaves | At two true leaves, first thinning to 1.2 in (3 cm) |
| Week 3 | Three or four true leaves | Pull crowded spots; water every two to three days |
| Week 4 | Four or five leaves, crowns whitening | Second thinning to 2 to 2.5 in (5 to 6 cm); feed and hill |
| Weeks 5 to 6 | Shoulders begin to show | Second hilling; keep moisture even |
| Week 7 | Shoulders 0.8 in (2 cm) up, finger thick | Test-pull for length; harvest the largest |
| Week 8 | Peak harvest | Clear the bed within two weeks; row cover if frost threatens |
A light frost browns the leaf edges but usually leaves the root unharmed. Trim the damaged leaves and pull soon after.
When you miss the window
Miss a sowing date and the long radish forgives you at the next one. Rather than forcing an out-of-season sowing, decide whether to compensate with row cover and netting or simply wait for the next season. What went wrong determines which.
| Situation | Left alone | Fix |
|---|---|---|
| Sown in mid fall or later | Matures into frost | Floating row cover; harvest small |
| Sown in late spring | Bolts before the root fills | Harvest young for greens and baby roots; resow in fall |
| Sown in summer | Pests and heat finish it first | Give up and resow in early fall |
| Sowed without removing stones | Bent, forked roots | Eat them anyway; deep-dig before the next sowing |
| Forgot the netting | Seed leaves eaten, seedlings stall | Keep the least-damaged plants, net, and resow the gaps |
Local differences and what to record
The same early-fall sowing matures one to two weeks apart between a mild coastal garden and a cooler inland one. Record three dates, the sowing, the first thinning and the first root pulled, and next year you can plan on your own garden's numbers instead of a packet's.
- Log the sowing date and variety Note the date, the variety and the number of rows. Days to harvest shift with variety and season, so this is the anchor.
- Log the first root pulled Write down the date you test-pulled and the root length. Next year in the same season you can count forward from sowing to predict harvest.
- Log the first frost Noting the first frost of the year lets you count backward to your last safe fall sowing date next season.