Grow Light for Geranium Seedlings: Long Indoor Starts
A grow light for geranium seedlings carries these starts through one of the longest indoor stretches of any bedding plant. NC State Extension notes that in poor light, pelargoniums become leggy plus bloom poorly. Sow early with bottom heat, hang lamps close plus pot up as plants grow.
The short answer
Start geranium seeds indoors 14 to 15 weeks before planting out, as University of Minnesota Extension suggests. Hang fluorescent or LED lights 2 to 4 inches above the seedlings plus run them 12 to 16 hours a day. Plant out after all danger of frost has passed plus the soil has warmed.
When should geranium seeds be sown?
Early. NC State Extension advises starting seeds indoors in January or February with bottom heat. University of Minnesota Extension lists geraniums among the flowers sown in early February, with 14 to 15 weeks indoors.
That long run is why lighting matters so much. Window light alone rarely carries a seedling for over three months. Clemson Extension notes that geraniums from seed are mainly single flowered types whose petals drop on their own, so spent blooms need little cleanup later.
| Stage | Light distance | Daily hours |
|---|---|---|
| Seedlings indoors | 2 to 4 inches above tops | 12 to 16 hours |
| Garden planting | Full sun | At least 4 hours of direct 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 so the gap stays the same. University of Maryland Extension also notes that seedlings grown under fluorescent or LED lights do much better than seedlings relying on natural light alone.
When should seedlings be potted up?
When roots fill the first cell. University of Minnesota Extension advises moving seedlings into larger containers as they grow. Crowded roots slow growth, which is costly over such a long indoor season.
Use a well drained mix. Clemson Extension notes that geraniums want well drained soil plus regular water, with the soil allowed to dry between waterings.
How to: step by step
- Start seeds inside in January or February over bottom heat.
- Maintain room air above 60°F.
- Set lamps 2 to 4 inches over the seedlings.
- Light seedlings 12 to 16 hours daily.
- Shift into bigger containers once roots fill each cell.
- Transplant outside once frost danger has passed plus the soil has warmed.
Troubleshooting
Leggy stems: weak light. NC State Extension notes that pelargoniums become leggy in insufficient light, so lower the lamp to 2 to 4 inches.
Slow growth: a cool room. University of Minnesota Extension advises air above 60°F for seed starting.
Crowded, stalled seedlings: roots out of room. Move each one to a larger container.
For related reading see cannabis seedling light schedule, leggy cannabis seedlings plus potting up cannabis seedlings. Kind Seed Co also stocks cannabis seeds.
Sources
- Geranium, Clemson Cooperative Extension Home and Garden Information Center
- Geraniums, University of Florida IFAS Gardening Solutions
- Pelargonium, NC State Extension Plant Toolbox
- Grow lights for starting seeds indoors, University of Maryland Extension
- Starting seeds indoors, University of Minnesota Extension
FAQ
How long do geraniums take from seed?
Plan on a long indoor stretch. University of Minnesota Extension suggests sowing geraniums in early February for 14 to 15 weeks indoors before planting out. NC State Extension advises starting seeds in January or February with bottom heat. Steady light plus warmth over that stretch gives sturdier plants.
Where should geraniums grow outdoors?
University of Florida IFAS notes that geraniums grow well in full sun but tolerate partial shade. Clemson Extension calls for at least 4 hours of direct sunlight daily plus well drained soil. Plant them after all danger of frost is past, once the soil has warmed.
Can geraniums be grown from cuttings instead?
Yes. Clemson Extension notes that most geraniums root easily from stem cuttings. Many cultivars must be grown this way to hold their flower or leaf color. NC State Extension adds that stem cuttings may be taken from July to August plus grown in a sunny window until frost passes.
Why are seedlings stretching?
Too little light. NC State Extension notes that pelargoniums become leggy plus bloom poorly in insufficient light. University of Maryland Extension advises lights no more than 4 inches above the seedling tops, with 2 inches as ideal, for 12 to 16 hours a day. Lower the lamp to fix it.
How often do geraniums need feeding outdoors?
Clemson Extension notes that geraniums usually need more fertilizer every four to six weeks during the growing season. Mix it into the soil well. A water soluble formula works well for follow up feedings, so plan a simple routine once plants settle into beds or containers.
