- Radishes do best when grown in cooler conditions, and are tolerant of cold weather.
- Loosen soil before planting at least six inches deep, a foot or more for long types.
- Plant seeds from April through early May, and again in August.
- Drought stress can cause the roots to develop poor flavor and tough texture.
- Harvest garden radishes three to five weeks after planting.
- Spade underneath the planting to harvest long daikon roots without breaking them.
Garden radishes and daikons
Radishes come in many sizes, colors, and types. Most familiar are the garden radishes (Raphanus sativus var. radicula). Garden radishes have a spicy flavor and crisp juicy texture. They are good in salads and can stand alone as a snack.
Radishes may be spherical or carrot-shaped, and in a rainbow of colors: green, white, pink, red, purple and yellow. You may plant these small roots in the spring, but you can also grow them as a fall crop.
Home gardeners can also grow the long, white, Asian radish (R. sativus var. longipinnatus), often called daikon, its Japanese name. These roots can grow to large sizes, and are typically less spicy or hot than the garden types. Gardeners often plant them in the late summer for a late fall harvest. You can store them for fresh use for up to two months.
Radishes do best when grown in cooler conditions, and are tolerant of cold weather. You can grow tender, juicy, flavorful radishes if the plants grow quickly without stress. They may develop a flower that goes to seed, develop excessively hot flavor or become woody during the heat of a typical Minnesota summer.
You should follow seed packet or catalog recommendations for individual varieties.
Soil pH and fertility
- Have your soil tested.
- Any well-drained, slightly acidic to neutral soil with pH 6 to 7 will do for radishes, as long as the soil is not compacted.
- Although daikon can penetrate heavy soils to depths more than one foot, the roots will not be as smooth, uniform and tender as those grown in lighter, prepared soils. If your soil is stony or very heavy, choose shorter daikon varieties.
- You can improve your soil by adding well-rotted manure or compost in spring or fall.
- Do not use fresh manure as it may contain harmful bacteria and increase weed problems. The readily available nitrogen can stimulate branching of the roots.
- Do not use any fertilizer containing a weed killer ("Weed and Feed"), as it may kill your vegetable plants.
- Prepare the radish bed by loosening soil at least six inches deep, a foot or more for long types. For daikon, create raised beds to ensure loosening of the soil and to make harvest easier.
- Plant radish seeds from early April through early May for a spring crop, and again August 1 through September 1 for a fall crop.
- Allow about one inch between seeds in the row.
- Plant the seed of smaller varieties shallowly, one-fourth to one-half inch deep. Plant larger varieties deeper, up to one inch deep. Seedlings will emerge within ten days.
- Heavy rains or excessive irrigation can cause soil crusting, which may weaken seedling emergence. If the soil surface has crusted, lightly sprinkling it to moisten and soften the crust may help.
- Thin radishes to about two inches between plants as soon as they reach a small, edible size. For larger varieties, such as daikons, allow four to six inches between plants. Pull any weeds in the row when thinning occurs.
Like other seedlings in the cabbage family, radishes have a distinct appearance: two fleshy cotyledons shaped like capital Bs, followed by true leaves that may be somewhat hairy and toothed.
How to keep your radishes healthy and productive
- Radish taproots can be large, but the horizontal roots do not extend far into the soil. Make sure they receive enough rainfall or deep watering.
- Drought stress can cause the roots to develop poor flavor and a tough texture.
- If the planting does not get one inch of rain each week, soak the soil thoroughly at least once a week.
- If your soil is sandy, it is important to water more often than once a week.
- An inch of water will wet a sandy soil to a depth of ten inches, a heavy clay soil to six inches.
- Use a trowel to see how far down the soil is wet. If it is only an inch or two, keep the water running.
- Radishes germinate and grow quickly. By the time you harvest garden radishes, weeds do not have a chance to become a problem.
- If you grow daikon, good weed control will be important for good yields and quality.
- Mulching with three to four inches of herbicide-free grass clippings, weed-free straw, compost, or other organic material will keep soil moisture and contain weeds, decreasing the need for frequent cultivation.
- Start cultivating with a hoe or other tool to remove weed seedlings while they are still small.
- Do not cultivate too deeply or you may damage the roots. Use a hand tool or a hoe, and cultivate just deeply enough to cut the weeds off below the surface.
- Root maggots feed on the developing roots.
- Flea beetles chew small, round holes in leaves. They can spread disease and destroy the crop, especially when the plants are very young.
- Use good cultural control practices to reduce disease problems to a good level and allow for a successful harvest.
- For assistance in diagnosing unknown problems, visit the University of Minnesota Extension diagnostic site “What’s wrong with my plant?”
Garden radishes are usually ready for harvest three to five weeks after planting. You can pull them any time they reach a usable size. They will get fibrous and develop a strong taste if left in the ground too long. Remove greens and wash roots well.
The daikon’s shoulders, or the top of the vegetable, typically stand up out of the soil, so the width of the root will be obvious. Spade or fork underneath the planting to harvest long daikon roots without breaking them. Remove the greens and wash the roots.
Daikon and garden radish will only keep for a week or two in the refrigerator. They lose moisture and become shriveled.
Reviewed in 2018