Grow Light for Sweet Alyssum Seedlings: Surface Sowing
A grow light for sweet alyssum seedlings suits a seed that needs light to germinate. Clemson Cooperative Extension advises covering the seed only lightly with soil. Sow near the surface, hang lights close plus set seedlings out around the last frost date.
The short answer
Sow sweet alyssum near the surface plus cover the seed only lightly, since Clemson Cooperative Extension notes that it needs light to germinate. Hang lights 2 to 4 inches above the seedlings for 12 to 16 hours a day, as University of Minnesota Extension advises. Set plants out around the last frost date.
Why sow alyssum on the surface?
Clemson Cooperative Extension notes that sweet alyssum seeds need light to germinate. Cover the seeds with soil only thinly.
Sweet alyssum can easily be grown from seed, the same source adds.
Clemson Cooperative Extension suggests sowing indoors 6 to 8 weeks before planting outdoors. NC State Extension gives a range of 5 to 6 weeks before the last frost date.
How close should lights hang?
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 timer makes the schedule simple to follow.
University of Maryland Extension notes that window light is seldom enough for good seedling growth. On a sill, seedlings usually stretch plus tilt toward the light.
| Setting | Guideline | Source note |
|---|---|---|
| Light height | 2 to 4 inches above seedlings | 2 inches is ideal |
| Light hours | 12 to 16 hours daily | Use a timer |
| Lamp type | Fluorescent or LED | Better than window light |
| Hardening off | Two weeks | Start in afternoon shade |
Source: University of Minnesota Extension plus University of Maryland Extension.
When should alyssum go outside?
NC State Extension advises setting out seedlings just before the last frost date. Sweet alyssum does well in full sun to partial shade in well drained soil.
University of Minnesota Extension advises hardening off over two weeks. Start with a few hours outside in shade during the warmth of the afternoon.
Clemson Cooperative Extension suggests a sunny spot that receives some afternoon shade. Plants grown from seed reach 3 to 6 inches high plus spread 12 inches or more.
How to: step by step
- Sow seed indoors 5 to 8 weeks before planting out.
- Cover the seed only lightly with soil.
- Hang lights 2 to 4 inches above the seedlings.
- Time lights for 12 to 16 hours daily.
- Harden off seedlings over two weeks.
- Move plants outdoors near the last frost date.
Troubleshooting
Patchy sprouting: seed buried too deep. Cover only lightly.
Stretched stems: lights too high. Lower them to 2 to 4 inches.
Seedlings collapsing: damping off in cool mix. Add bottom heat.
For related reading see cannabis seedling light schedule, leggy cannabis seedlings plus damping off cannabis seedlings. Kind Seed Co also stocks cannabis seeds.
Sources
- Lobularia maritima (sweet alyssum), NC State Extension Gardener Plant Toolbox
- Sweet alyssum, Clemson Cooperative Extension Home plus Garden Information Center
- Grow lights for starting seeds indoors, University of Maryland Extension
- Starting seeds indoors, UMN Extension
FAQ
Can sweet alyssum be direct sown?
Yes. Clemson Cooperative Extension notes that sweet alyssum should be directly sown in the garden several weeks before the last frost date in spring. Seeds can also be sown in September for fall into winter flowers. NC State Extension suggests August sowing for fall bloom.
How fast does sweet alyssum flower?
Clemson Cooperative Extension notes that plants will flower within 6 to 8 weeks of sowing. NC State Extension adds that sweet alyssum produces spreading mounds of fragrant white flowers from spring to first frost where summers are cool. That quick bloom suits a short indoor start.
Does alyssum bloom in summer heat?
Clemson Cooperative Extension notes that as summer temperatures rise, alyssum grown from seed may stop producing flowers. NC State Extension also says blooms decline in hot summers. Sterile hybrids with better heat resistance exist, but Clemson notes they are not available as seeds.
Should alyssum be cut back?
Yes. NC State Extension advises cutting plants back during the summer or when the blooms decline to help them flower longer. In spring, removing old plants exposes self sown seedlings, the same source notes. Light afternoon shade can also help in hot areas.
Why do alyssum seedlings collapse?
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.
