Grow Light for Coleus Seedlings: Compact Colorful Starts
A grow light for coleus seedlings holds these foliage starts compact before they move outdoors. University of Florida IFAS describes coleus as a plant prized for leaves in green, yellow, pink, red, orange plus maroon. Sow in early spring, hang lamps close plus pinch tips for bushy plants.
The short answer
Start coleus seeds indoors about 10 to 11 weeks before planting out, as University of Minnesota Extension suggests. Hang fluorescent or LED lights 2 to 4 inches above the seedlings for 12 to 16 hours a day. Pinch the growing tips often, then plant out after frost.
Why do coleus seedlings need close light?
Weak light makes them stretch. NC State Extension notes that full shade may lead to leggy coleus growth, even though the plant tolerates shade once grown. Indoors, a window rarely gives seedlings enough light to stay compact.
University of Maryland Extension notes that seedlings grown under fluorescent or LED lights do much better than seedlings relying on natural light alone.
| Stage | Light distance | Daily hours |
|---|---|---|
| Seedlings indoors | 2 to 4 inches above tops | 12 to 16 hours |
| Garden planting | Part shade or dappled light | Sun tolerant cultivars take full sun |
Source: University of Maryland Extension plus Clemson Extension.
How close should lights hang?
Very close. University of Maryland Extension advises lights no more than 4 inches above the seedling tops, with 2 inches as ideal. It suggests 12 to 16 hours of light daily.
Raise the fixture as the plants grow. University of Minnesota Extension advises room air above 60°F while seedlings develop.
Why pinch coleus seedlings?
Pinching makes branches. Clemson Extension advises pinching the growing shoots of young plants often to encourage branching plus dense foliage. University of Florida IFAS adds that removing flowers appears to stop plants from going to seed plus declining.
NC State Extension agrees that pinching the stem tips can make the plant bushier. Start once seedlings have a few pairs of leaves.
How to: step by step
- Start seeds inside in early March for 10 to 11 weeks under lights.
- Maintain room air above 60°F.
- Position lamps 2 to 4 inches over the seedlings.
- Light seedlings 12 to 16 hours daily.
- Nip tips after plants form a few leaf pairs.
- Acclimate outdoors, then plant out after frost has passed.
Troubleshooting
Leggy stems: lights too high or too dim. Lower the lamp to 2 to 4 inches plus pinch the tips.
Slow sprouting: a cold mix. University of Minnesota Extension notes that seeds germinate sooner when the potting mix is warm.
Wilting after planting out: too much sun. NC State Extension notes that coleus may wilt in full sun, so choose part shade or a sun tolerant cultivar.
For related reading see cannabis seedling light schedule, leggy cannabis seedlings plus hardening off cannabis seedlings. Kind Seed Co also stocks cannabis seeds.
Sources
- Coleus, University of Florida IFAS Gardening Solutions
- Coleus, Clemson Cooperative Extension Home and Garden Information Center
- Coleus scutellarioides, NC State Extension Plant Toolbox
- Starting seeds indoors, University of Minnesota Extension
- Grow lights for starting seeds indoors, University of Maryland Extension
FAQ
How long does coleus take from seed?
University of Minnesota Extension lists coleus among the flowers sown in early March, with about 10 to 11 weeks indoors before planting out. Clemson Extension notes that coleus grows rapidly to full summer size once it is in the ground, so a timely indoor start pays off quickly.
Can coleus grow in shade?
Yes. Clemson Extension notes that most coleus grow well in part shade or dappled light. NC State Extension adds that it even tolerates full shade, though full shade may lead to leggy growth. Several sun tolerant cultivars are also available for brighter spots in the garden.
When should coleus go outside?
After frost. Clemson Extension notes that coleus are tender annuals killed by the first frost. Plant seedlings out once frost danger has passed plus nights are warm. Harden them off first, since plants raised under lights have not faced sun, wind or shifting temperatures.
Can coleus be grown from cuttings?
Yes. NC State Extension notes that cuttings root easily in water or clean potting soil. Clemson Extension adds that vegetative coleus are sterile cultivars that must be grown from cuttings. Seed grown types suit gardeners who want many plants from a single packet.
Should coleus flowers be removed?
Usually. Clemson Extension notes that many people dislike the flower spikes, plus a plant allowed to go to seed will decline. It suggests shearing or pinching back flowers to extend performance. University of Florida IFAS also advises removing flowers to stop plants from going to seed.
