Grow Lights for Radishes Indoors: Deep Tray Method
Grow lights for radishes indoors can produce round roots when light is bright plus trays are deep enough. UF/IFAS notes radishes are an ideal container crop that reaches harvest size within weeks. Use a deep tray of loose mix, thin seedlings plus hang lamps close for long days.
The short answer
Loosen mix at least six inches deep, as University of Minnesota Extension advises for garden radishes, thin plants to about two inches apart plus hang lights close. Iowa State University Extension gives 14 hours a day under most grow lights. Pull roots 20 to 30 days after sowing while young.
Why do indoor radishes make leaves but no roots?
Slow growth plus crowding are the causes the sources point to. University of Illinois Extension notes slow development makes radishes hot plus woody plus that proper thinning focuses the harvest. University of Minnesota Extension notes tender roots come from plants that grow quickly without stress. Iowa State University Extension notes light is often the most limiting growth factor indoors.
How deep should radish trays be?
University of Minnesota Extension advises loosening soil at least six inches deep for garden radishes plus a foot or more for long types. Sow small varieties one fourth to one half inch deep.
| Radish type | Mix depth | Spacing |
|---|---|---|
| Small round types | At least 6 inches of loose mix | About 2 inches apart |
| Long daikon types | A foot or more | 4 to 6 inches apart |
| Broadcast on a bed | Loose prepared mix | 2 to 3 inches in all directions |
Source: University of Minnesota Extension plus University of Illinois Extension.
When are indoor radishes ready?
UF/IFAS advises harvesting radishes on the younger side, 20 to 30 days after sowing. University of Illinois Extension advises pulling them at usable size, usually when roots are under 1 inch across, since they stay in harvest condition only a short time before turning pithy plus hot.
How to: step by step
- Fill a tray at least six inches deep with loose potting mix.
- Sow seed one fourth to one half inch deep.
- Thin seedlings to roughly two inches apart.
- Hang lights close above the plants plus run them 14 hours a day.
- Water evenly plus hold the room cool.
- Lift roots 20 to 30 days from sowing.
Troubleshooting
Leaves but small roots: crowding or slow growth. Thin plants plus drop the lights.
Tough roots with poor flavor: drought stress. Water steadily.
Woody or pithy roots: left too long. Harvest earlier.
For related reading see grow lights for cannabis, led light distance cannabis plus grow light timers. Kind Seed Co also stocks seeds for indoor growers.
Sources
- Radishes, UF/IFAS Gardening Solutions
- Growing radishes in home gardens, University of Minnesota Extension
- Radish, home vegetable gardening, University of Illinois Extension
- How to set up supplemental lights for indoor plants, Iowa State University Extension
FAQ
Can radishes grow in a window?
University of Illinois Extension notes spring radishes can be planted in late winter in a window box or container in the house. Iowa State University Extension notes nearly all indoor plants benefit from supplemental light in winter, so a grow light helps where window light is weak or days are short.
How long do indoor radishes take?
UF/IFAS advises harvesting radishes 20 to 30 days after sowing, with larger varieties taking longer. University of Minnesota Extension lists garden radishes as usually ready three to five weeks after planting plus notes seedlings emerge within ten days. Check roots often, since they mature quickly.
Which radish types suit trays?
Small round types suit trays. UF/IFAS lists Cherry Belle, Sparkler plus Champion as round varieties. Long daikon types need a foot or more of loose soil according to University of Minnesota Extension, so they suit deep containers rather than shallow trays under a light.
Why do radish greens turn tough?
UF/IFAS notes older greens are tougher plus more peppery than young ones. Both roots plus greens turn tough plus bitter as they mature, mainly in hot weather, so harvest young. UF/IFAS advises harvesting radishes on the younger side, 20 to 30 days after sowing.
What temperature suits indoor radishes?
UF/IFAS notes radishes prefer cooler temperatures plus that the bitter, peppery flavor is more intense when they grow warm. University of Minnesota Extension notes radishes may go to seed, turn too hot or become woody in summer heat. A cool room under lights suits the crop.
