Sweet alyssum (Lobularia maritima) is a low, spreading annual with clusters of tiny, fragrant flowers. University of Wisconsin Horticulture Extension lists plants at 3 to 9 inches tall and wider than tall, flowering through the growing season. Growth slows in hot weather but recovers as temperatures cool.
Sweet Alyssum at a glance
| Type | Flower |
|---|---|
| Season | Cool-season |
| Sun | Full sun |
| Plant spacing | 10 in |
| Row spacing | 10 in |
| Per square foot | 1 |
| Seed depth | 0.05 in |
| Days to maturity | Flowers 6–8 weeks after sowing |
| How to start | Plants usually begin flowering 6 to 8 weeks after sowing. |
| Water | 1 in per week |
These are the same numbers our plant spacing, square foot and harvest date calculators use. See every crop in the plant database.
When to plant sweet alyssum
Plants usually begin flowering 6 to 8 weeks after sowing. Tender transplants need protection until frost danger has passed. Use the frost dates by ZIP code and planting calendar.
How to plant sweet alyssum
- Choose full sun in cool climates; partial shade may work better in hot ones.
- Use average, well-drained soil with medium moisture.
- Leave room to spread. Cultivars spread about 8 to 12 inches; use the plant spacing calculator.
Caring for sweet alyssum
It does best with consistent moisture but tolerates short dry spells; see the garden watering calculator. Deadheading produces more flowers. Shear back leggy or overgrown plants, or ones with more seedpods than flowers, to tidy them and encourage reflowering; light shearing, watering and light feeding help plants recover in summer.
Companion plants
| Grow nearby | Lettuce, broccoli, snapdragons and pansies |
|---|---|
| Keep apart | Dense, wet, crowded planting |
The flowers attract beneficial insects, and California growers plant alyssum in lettuce and broccoli fields to help control aphids. Check other pairings with the companion plant finder.
Common problems
| Problem | What you see | What to do |
|---|---|---|
| Ragged summer look | Slow growth and fewer flowers in heat | Growth and flowering slow in hot weather. Shear back; plants recover and bloom well into fall. 'Snow Crystals' and 'Snow Princess' have improved heat tolerance. |
| Rot in crowded growth | Mushy stems in dense, wet planting | Dense, wet or crowded growth can rot; give plants air and avoid overwatering. |
Not sure what you are looking at? The plant problem identifier ranks likely causes from the symptoms you see.
When and how to harvest
Sweet alyssum is grown for its flowers and as a pollinator and beneficial-insect plant. It may reseed, but not aggressively; seedlings from named cultivars often have white flowers and are taller than the parent.
Plan your sweet alyssum
- Plant spacing calculator: how many plants fit your bed
- Planting calendar: sowing and transplant dates for your frost dates
- Frost dates by ZIP code: your last spring and first fall frost
- Harvest date calculator: when your crop will be ready
Frequently asked questions
How far apart should I plant sweet alyssum plants?
Space sweet alyssum plants 10 inches apart in rows 10 inches apart. In a square foot garden, plant 1 per square foot.
How deep do I plant sweet alyssum seeds?
Leave room for plants to spread about 8 to 12 inches; flowering begins 6 to 8 weeks after sowing.
How long do sweet alyssum plants take to grow?
Plants usually start flowering 6 to 8 weeks after sowing.
How much water do sweet alyssum plants need?
About 1 inch of water a week, from rain and watering combined. Keep moisture consistent; short dry spells are tolerated.
Why is my alyssum straggly in summer?
Heat slows growth and flowering. Shear it back, water and feed lightly, and it will recover and bloom into fall.
Does sweet alyssum reseed?
It may, but not aggressively; seedlings from named cultivars often have white flowers.
Does sweet alyssum help beneficial insects?
Yes, the flowers attract beneficial insects.