Grow Light for Cauliflower Seedlings: Compact Starts
A grow light for cauliflower seedlings has one job: give enough light, close enough, for long enough that starts grow short plus sturdy. Illinois Extension notes leggy seedlings come from too little light. University of Maryland Extension notes stressed or overgrown transplants can button. Compact starts give the crop a better chance.
The short answer
Set the light close plus run it on a timer. University of Maryland Extension places fluorescent tubes 1 to 2 inches above seedlings for 14 to 16 hours a day. University of Minnesota Extension suggests 2 to 4 inches for 12 to 16 hours. Illinois Extension advises no more than 18 hours.
How close should the light be?
Illinois Extension notes leggy growth comes from too little light, so a light hung high gives stretched seedlings. University of Maryland Extension advises fluorescent lights 1 to 2 inches above the plants. University of Minnesota Extension suggests 2 to 4 inches. Illinois Extension notes LEDs tend to give compact seedlings. Raise the light as the seedlings grow.
| Factor | Guide | Source |
|---|---|---|
| Light height | 1 to 2 inches (fluorescent) | University of Maryland |
| Light height | 2 to 4 inches | University of Minnesota |
| Hours per day | 14 to 16 | University of Maryland |
| Hours per day | 18 at most | Illinois Extension |
| Night after germination | 55 to 60 F | University of Maryland |
| Day after germination | 65 to 70 F | University of Maryland |
Source: University of Maryland Extension, University of Minnesota Extension plus Illinois Extension.
How long should the light run?
Illinois Extension suggests about 16 hours of light a day on a timer, with 18 hours as the most. University of Maryland Extension suggests 14 to 16 hours. Plants still require a dark period each day. A simple timer steadies the schedule.
When are cauliflower starts ready?
University of Maryland Extension advises setting out transplants at five to seven weeks old. It sets this for three to four weeks before the frost free date. It notes stressed or overgrown transplants can button, forming small early heads. After germination it suggests nights of 55 to 60 F plus days of 65 to 70 F.
How to: step by step
- Count back five to seven weeks from your planting date.
- Hang the light 1 to 4 inches above the tray.
- Set a timer for 14 to 16 hours.
- Drop the room to 55 to 60 F at night after germination.
- Lift the light as seedlings grow.
- Transplant before the starts get overgrown.
Troubleshooting
Tall, leggy seedlings: too little light. Lower the light plus confirm the hours.
Small early heads after planting: stressed or overgrown transplants. Transplant at five to seven weeks.
Leggy starts despite long hours: light too high. Lower it to 1 to 4 inches.
For related reading see cannabis seedling light schedule, leggy cannabis seedlings plus hardening off cannabis seedlings. Kind Seed Co also stocks cannabis seeds.
Sources
- Growing cauliflower in a home garden, University of Maryland Extension
- Grow lights for starting seeds indoors, University of Maryland Extension
- Care of vegetable seedlings, University of Maryland Extension
- Supplemental lighting for indoor seed starting, Illinois Extension
- Starting seeds indoors, University of Minnesota Extension
FAQ
How far should a grow light be from cauliflower seedlings?
University of Maryland Extension advises fluorescent lights 1 to 2 inches above seedlings. University of Minnesota Extension suggests 2 to 4 inches. A light hung too high gives tall, weak starts. Raise the light as the seedlings grow so the tips stay just below it, and check the height every few days.
How many hours of light do cauliflower seedlings need?
University of Maryland Extension suggests 14 to 16 hours a day. Illinois Extension suggests about 16 hours on a timer and advises no more than 18 hours. Seedlings still need a dark period each day. A timer holds the schedule steady, so the lights do not depend on memory.
Are LED lights good for cauliflower starts?
Yes. Illinois Extension notes LED lights tend to give compact seedlings. That matters for cauliflower, since University of Maryland Extension notes stressed or overgrown transplants can button. Follow the maker's guide for hanging height with an LED fixture, and watch the seedlings for stretching or pale leaves as a sign to adjust.
Why are my cauliflower seedlings leggy?
Illinois Extension notes leggy seedlings come from too little light. Lower the light, check that the timer runs 14 to 16 hours, and cool the room at night. University of Maryland Extension suggests nights of 55 to 60 F plus days of 65 to 70 F after germination for sturdier growth.
When should cauliflower seedlings go outside?
University of Maryland Extension advises setting out transplants at five to seven weeks old. It suggests doing this three to four weeks before the frost free date in spring. It notes stressed or overgrown transplants can button and form small early heads. Plan the seed date so starts reach the garden on time.
