Grow Light for Celery Seedlings: A Long Indoor Start
A grow light for celery seedlings has a long stretch of work. Utah State University Extension notes celery is started from seed around February 1, then transplanted in April or early May. That is many weeks under lights. Close light, a timer plus cool, even temperatures carry the seedlings through.
The short answer
Hang the light 2 to 4 inches above the seedlings, as University of Minnesota Extension suggests, for 12 to 16 hours a day. Soak seeds first to help germination. Utah State University Extension notes celery likes 55 to 65 F. Transplant once seedlings have 3 to 4 mature leaves.
How much light do celery seedlings need?
University of Minnesota Extension advises lights no more than 4 inches above seedlings, with 2 inches as ideal. It notes lack of light is the major cause of elongated, skinny stems. It suggests 12 to 16 hours of light daily with a dark period. Illinois Extension advises 18 hours at most for seedlings.
| Factor | Guide | Source |
|---|---|---|
| Sowing time | Around February 1 | Utah State University |
| Transplant time | April or early May | Utah State University |
| Transplant size | 3 to 4 mature leaves | Utah State University |
| Ideal temperature | 55 to 65 F | Utah State University |
| Light height | 2 to 4 inches | University of Minnesota |
| Hours per day | 12 to 16 | University of Minnesota |
Source: Utah State University Extension plus University of Minnesota Extension.
Why is celery slow to germinate?
Utah State University Extension notes celery seed contains natural germination inhibitors. Soaking helps leach them away. It advises soaking seeds in water plus changing the water every day. Germination is then more uniform. University of Minnesota Extension notes some seeds require light to germinate, so cover them only thinly.
What temperatures does celery like?
Utah State University Extension notes the ideal temperature for celery is 55 to 65 F. It notes plants exposed to cool temperatures for several weeks will flower. It notes celery is very susceptible to frost, so young transplants need cover outdoors.
How to: step by step
- Soak seeds in water, renewing it daily.
- Sow near February 1 in a seed starting mix.
- Hang the light 2 to 4 inches over the tray.
- Set a timer for 12 to 16 hours.
- Raise seedlings near 55 to 65 F.
- Transplant when plants carry 3 to 4 mature leaves.
Troubleshooting
Patchy germination: natural inhibitors in the seed. Soak seeds plus change the water daily.
Skinny, stretched seedlings: too little light. Lower it to 2 to 4 inches.
Plants flowering early: weeks of cool temperatures. Avoid long cold spells after planting.
For related reading see cannabis seedling light schedule, leggy cannabis seedlings plus hardening off cannabis seedlings. Kind Seed Co also stocks cannabis seeds.
Sources
- Celery in the garden, Utah State University Extension
- Starting seeds indoors, University of Minnesota Extension
- Supplemental lighting for indoor seed starting, Illinois Extension
FAQ
When should celery seeds be started?
Utah State University Extension notes celery is started from seed around February 1. It is then transplanted in April or early May, depending on your area. That makes celery one of the longer indoor starts. Plan your light setup for many weeks of use rather than a short spring run.
Should celery seeds be soaked?
Yes. Utah State University Extension notes celery germinates better when seeds soak in water that is changed every day. The seed contains natural germination inhibitors, and soaking helps leach them away. Sow the seeds after soaking and cover them only thinly, since some seeds need light to germinate.
How far should the light be from celery seedlings?
University of Minnesota Extension advises lights no more than 4 inches above seedlings, with 2 inches as ideal. It suggests hanging lights from chains so they are easy to raise. Lift the light as the celery grows so the gap stays small, which gives sturdier, shorter stems.
How many hours of light do celery seedlings need?
University of Minnesota Extension suggests 12 to 16 hours of light daily. It advises against leaving lights on all the time, since many plants need a dark period each night. Illinois Extension advises 18 hours at most for seedlings. A simple timer runs the schedule the same way every day.
When are celery transplants ready?
Utah State University Extension notes transplants should have 3 to 4 mature leaves plus a well established root system before planting. It notes celery is very susceptible to frost, so cover young plants with row covers or hot caps when cold nights are forecast after transplanting into the garden.
