Also receive the Almanac Daily newsletter including gardening tips, weather, astronomical events, and more.
Planting, Growing, and Caring for Lobularia Maritima
Sweet alyssum is a pretty flowering plant that forms a low-spreading mound with tiny, sweet-smelling blooms throughout the growing season. It’s pollinator-friendly and commonly used as a seasonal ground cover or annual bedding flower. Learn how to plant, grow, and care for sweet alyssum.
About Sweet Alyssum
Sweet alyssums (Lobularia maritime) are commonly treated as annual plants in most of North America, even though they are perennials in their native Mediterranean climate. In zones 9 to 11, they can be grown as tender perennials, which means that they won’t survive frost. (Check your updated zone here).
Sweet alyssum is considered a cool-weather bloomer. It often displays blooms in spring, takes a break in hot weather, and reblooms in early autumn as the daytime highs begin to come down.
The flowers are typically white, four-petaled, and small, growing in clusters called racemes. They can also be lavender or purple in color. With their honey-like fragrance, alyssum is loved by the smaller pollinators, and their nectar is easily accessible to beneficial insects.
These plants are easy to start from seed and are also commonly available in flats or six-packs in garden centers in springtime. Usually reaching only 3 to 9 inches high but sprawling as far as 2 to 3 feet wide, they’ll gently spread out and provide a flowering, three-dimensional carpet that is much more interesting than bagged mulch. Some varieties will spread quite willingly and can be used at the edge of paths to spill over paving stones, fill in stony crevices, or as the spiller in a traditional thriller-filler-spiller container planting.
***Sweet alyssum is considered an invasive species in California. It can rapidly take off and spread in frost-free areas, so check with your state before planting if you live in an area without winter freezing temps.***
Planting
Sweet alyssum blooms and spreads best in full sun but will do well in a location with afternoon shade in arid climates or the hotter proportions of its range. It tolerates sandy or rocky conditions and does best with a neutral or slightly acidic pH. Avoid soggy locations. Young plants are not frost tolerant, but mature plants will tolerate a light frost without damage.
One or two plants are enough to provide interest in a container, but when planting sweet alyssum in a garden bed, go for the more-is-better look. They’ll happily crowd together and make a thick layer of foliage and blooms, and the carpet of color is worth a bit of extra work in spring.
When to Plant Sweet Alyssum
When planting nursery-started plants, wait until after the last frost has passed. Remember to harden them off if needed. Sweet alyssum can also be started from seed indoors at home for transplanting.
If you start sweet alyssum seeds indoors, do so 8 to 10 weeks before your last frost date. Once the soil has warmed to about 60 degrees, sweet alyssum can be directly seeded in the garden.
How to Plant Sweet Alyssum
Sweet alyssum is commonly purchased in flats or packs of small plants from a garden center or nursery, although they are also easy to start from seed. To transplant sweet alyssum, follow these steps.
- Water the plugs or flats several hours before transplanting to reduce plant stress.
- For in-ground planting, prepare the soil by working in a layer of compost. Any high-quality potting soil is fine for container growing.
- For larger plantings, remove the sweet alyssum plants from their containers and set them out where they’ll be planted, spacing them 8 to 12 inches apart. Pre-arranging before planting will allow you to space them for better coverage and avoid leaving gaps as you finish. You can also play with colors and patterns.
- Use a hand trowel and dig a small hole, as deep as the plug and a bit wider. Loosen the soil at the bottom.
- Set the sweet alyssum plant or plug in the hole, check the depth, and refill the hole, firming the soil around the roots as you go.
- Grab the hose and give them a good soaking.
- Add mulch to keep weeds down and soil moisture up while the plants get established. Use natural mulch that will decompose quickly, such as shredded straw, pine needles, or grass clippings.
Sweet alyssum can also be broadcast sown directly onto garden beds in spring. Sow them in spring once the soil has thawed, about 2 to 3 weeks before your last frost. The seeds need light to germinate, but they will do better if gently pressed into the soil for good seed-to-soil contact.
If bird predation is an issue, dust the area with a thin layer of vermiculite or finely shredded straw. The layer should be thin enough that some light still gets through.
Growing
Sweet alyssum likes evenly moist soil and supplemental watering in dry periods. While it will tolerate a bit of drought, growth and flowering will be affected. Like many plants, excess fertilizing will cause a flush of vegetative growth at the expense of flowering. Compost worked into the soil in spring will likely be sufficient.
While deadheading encourages more blooms, it can be daunting if you have a larger groundcover planting of sweet alyssum.
- For single plants in a container, just nip off the spent blooms.
- In larger plantings, give the entire grouping a haircut with a hedge trimmer or other similar tool. Take off the top third of the plant when you notice many blooms are tired or the plant is getting leggy. You’ll encourage bushier growth and accomplish deadheading without spending hours on the task.
Types
- ‘Pastel Carpet’ provides a flowing border of color in large plantings. Its blooms are light shades of cream, pink, rose, and purple. This variety reaches about nine inches high and spreads to about a foot in diameter, so plant it closer together.
- ‘Rosie O’Day’ is an AAS winner for bedding plants. Its smaller stature—only six inches high and spreading to about a foot wide—makes it perfect for providing lovely purple features in containers and planters.
- ‘Carpet of Snow’ gives you an idea of how many blossoms this variety produces. A bit hardier than most, it is rated for USDA zone 7. Plant en masse for easy groundcover. You can start from seed.
See 10 of our favorite ground cover plants.
Andy Wilcox
ADVERTISEMENT
