Grow Light for Tomatillo Seedlings: Warm Indoor Starts
A grow light for tomatillo seedlings pairs well with a warm start. Utah State University Extension advises germinating seed at 80°F until the root emerges. Seedlings then grow on at 65 to 70°F under close lamps for six to eight weeks before planting out.
The short answer
Utah State University Extension advises germinating tomatillo seed at 80°F until the seed root emerges, then growing on at 65 to 70°F. Allow six to eight weeks to grow transplants. University of Minnesota Extension advises lamps no more than 4 inches above seedlings plus 12 to 16 hours of light daily.
How warm should tomatillo seed be?
Utah State University Extension advises germinating tomatillo seeds at 80°F until the seed root emerges. Seedlings then move into sterile seeding mix plus grow out at 65 to 70°F.
University of Minnesota Extension notes that a constant heat source from underneath can be very beneficial to seedlings. Warmth below helps seeds sprout sooner.
Air temperatures should stay above 60°F when bottom heat is provided, the same source advises.
How close should lights sit?
University of Minnesota Extension advises lights no more than 4 inches above the tops of seedlings. As close as 2 inches is ideal.
Plants need 12 to 16 hours of light daily, the same source notes. A simple timer can turn lights off plus on automatically.
University of Minnesota Extension also advises a seed starting spot away from cold drafts plus excess heat. Too much daytime heat can dry the potting mix.
| Stage | Guideline | Source note |
|---|---|---|
| Germination | 80°F until the root emerges | Warm start |
| Grow out | 65 to 70°F | After sprouting |
| Lamp height | 2 to 4 inches above seedlings | Close is ideal |
| Ready to plant | Five to seven leaves | Six to eight weeks |
Source: Utah State University Extension plus University of Minnesota Extension.
When are tomatillo transplants ready?
Utah State University Extension advises allowing six to eight weeks to grow transplants. Plants should have five to seven leaves plus a well developed root system before planting.
Transplant or seed directly in the garden after danger of frost has passed, the same source advises. UF IFAS Gardening Solutions notes that tomatillo is sensitive to frost damage.
University of Minnesota Extension advises hardening off seedlings over about two weeks. Pot up into containers 1 to 2 inches wider when roots fill their cells.
How to: step by step
- Germinate seed at 80°F on a heat mat.
- Shift sprouts into sterile seeding mix.
- Raise them at 65 to 70°F.
- Set lamps 2 to 4 inches above seedlings for 12 to 16 hours.
- Pot up once roots fill the cells.
- Plant out after frost once plants have five to seven leaves.
Troubleshooting
Slow sprouting: cool mix. Use bottom heat near 80°F.
Tall thin stems: lamps too high. Lower them to 2 to 4 inches.
Frost damaged leaves: planting out too early. Wait until frost has passed.
For related reading see cannabis seedling light schedule, seedling heat mats for cannabis plus potting up cannabis seedlings. Kind Seed Co also stocks cannabis seeds.
Sources
- Tomatillos in the garden, Utah State University Extension
- Tomatillos, UF IFAS Gardening Solutions
- Physalis philadelphica (tomatillo), NC State Extension Gardener Plant Toolbox
- Starting seeds indoors, UMN Extension
FAQ
How early should tomatillos be started?
Utah State University Extension advises starting plants indoors six to eight weeks before the planting date. Transplant or seed directly in the garden after danger of frost has passed. Plants should have five to seven leaves plus a well developed root system before they go out.
How big do tomatillo plants get?
NC State Extension notes that these indeterminate plants grow 3 to 4 feet in height plus width. UF IFAS Gardening Solutions describes the plants as large plus sprawling. The NC State page adds that stems root easily on contact with soil, so a cage or trellis helps.
Do tomatillos need more than one plant?
Yes. Utah State University Extension advises planting at least two tomatillo plants for proper pollination. NC State Extension adds that tomatillo plants are not great at self pollinating. Start a few seedlings under lights so more than one plant goes into the garden.
What sun do tomatillos need outside?
NC State Extension advises planting tomatillos in full sun in moist, rich, well drained garden soil. Set them out as transplants after the threat of frost in late spring. Start hardening seedlings off about two weeks before that date, per University of Minnesota Extension.
Can tomatillos be direct seeded?
Yes. Utah State University Extension notes that you can transplant or seed directly in the garden after danger of frost has passed. UF IFAS Gardening Solutions adds that both tomatillos plus husk tomatoes start well from seed. An indoor start under lights simply gives plants a head start.
