Grow Light for Lobelia Seedlings: Close Lamps Plus 16 Hours
A grow light for lobelia seedlings helps a plant that NC State Extension calls difficult to grow from seed. University of Illinois Extension sets fluorescent tubes a few inches above seedlings for 16 hours a day. Plant out in spring, since lobelia does much better in cool weather.
The short answer
Set fluorescent or LED lights a few inches above lobelia seedlings plus run them about 16 hours a day, as University of Illinois Extension describes. University of Minnesota Extension advises 2 to 4 inches above the tops. NC State Extension notes that lobelia does much better with cool springs than hot summers.
Why is lobelia hard from seed?
NC State Extension notes that edging lobelia can be difficult to grow from seed. An annual planting of purchased plants can be more successful, the same source adds.
Indoors, good light comes first. University of Illinois Extension notes that the most common seed starting problem it sees is inadequate light.
Without enough light, plants are leggy, the same source explains. Leggy describes long stem sections between the leaves due to low light.
How close should lights hang?
University of Illinois Extension notes that fluorescent tubes produce very little heat. So the fixture can sit just a few inches above the plants.
University of Minnesota Extension advises lights no more than 4 inches above seedlings, with 2 inches ideal. University of Illinois Extension gives seedlings 16 hours of light per day, with 18 hours as the maximum.
University of Illinois Extension adds that LEDs are highly efficient at turning electricity into light. Commercial growers using LEDs report uniform, compact plus sturdy seedlings.
| Setting | Guideline | Source note |
|---|---|---|
| Light height | 2 to 4 inches above seedlings | A few inches with fluorescent tubes |
| Light hours | About 16 hours daily | 18 hours maximum |
| Lamp type | Fluorescent or LED | Little heat from tubes |
| Hardening off | Two weeks | Before planting out |
Source: University of Illinois Extension plus University of Minnesota Extension.
Does lobelia like heat?
NC State Extension notes that lobelia seems to do much better with cool springs than with hot or humid summers. North of zone 10 it is often grown as an annual.
The plant is relatively small at 4 to 9 inches, the same source notes. It produces heavy blooms of colorful flowers in late spring well into the summer.
NC State Extension suggests full sun to part shade in organically rich, moist, well drained soil. University of Minnesota Extension advises hardening off seedlings over two weeks before planting out.
How to: step by step
- Fill cells with moist seed starting mix.
- Start lobelia seed indoors under lights.
- Hang lights 2 to 4 inches above the seedlings.
- Time the lights for about 16 hours daily.
- Harden seedlings off over two weeks.
- Plant out in spring while weather stays cool.
Troubleshooting
Thread thin seedlings: lights too high. Lower them to 2 to 4 inches.
Seedlings collapsing: damping off in cool mix. Add bottom heat.
Slow growth: lobelia is difficult from seed. Consider purchased plants.
For related reading see cannabis seedling light schedule, leggy cannabis seedlings plus damping off cannabis seedlings. Kind Seed Co also stocks cannabis seeds.
Sources
- Lobelia erinus (edging lobelia), NC State Extension Gardener Plant Toolbox
- Starting a garden: supplemental lighting for indoor seed starting, University of Illinois Extension
- Grow lights for starting seeds indoors, University of Maryland Extension
- Starting seeds indoors, UMN Extension
FAQ
How many hours of light do lobelia seedlings need?
University of Illinois Extension gives seedlings 16 hours of supplemental light per day, with 18 hours as the maximum. University of Minnesota Extension gives a range of 12 to 16 hours daily. An automatic timer makes either schedule easy to follow without daily attention.
Can lobelia grow in hanging baskets?
Yes. NC State Extension notes that trailing forms of lobelia are excellent for hanging baskets, while the upright form suits edging plus flower beds. The cultivar Hamburgia is a trailing form suitable for hanging baskets or raised planters, according to the same source.
When does lobelia bloom?
NC State Extension notes that edging lobelia typically blooms from April to June. Flowers are white, scarlet or blue with two lips plus a yellow to white throat. The plant produces heavy blooms in late spring well into the summer where conditions stay cool.
Why do lobelia seedlings damp off?
University of Minnesota Extension describes damping off as the death of tiny seedlings due to pathogens at the surface of the potting mix. Bottom heat can help prevent it. Cooler soil temperatures can lead to seedling death due to disease, the same source adds.
Can lobelia grow in shade?
NC State Extension lists full sun to part shade for edging lobelia. It does much better with cool springs than with hot or humid summers. It is often grown as an annual north of zone 10 plus stays relatively small at 4 to 9 inches.
