Sweet alyssum (Lobularia maritima 'Snow Crystals')
Lobularia maritima 'Snow Crystals' (Sweet alyssum) offers fragrant, showy white flowers from spring to frost; tough and drought tolerant.
Complete Plant Information
Overview
Sweet alyssum, particularly the vigorous variety Lobularia maritima ‘Snow Crystals’, is highly valued for creating a low, dense carpet of intensely fragrant white blooms. This plant is renowned for its ease of cultivation, often smothering its fine, gray-green foliage with flowers from the time it is planted until frost in cooler climates. It serves as an indispensable edging or mass planting option, bringing reliable texture and scent to garden spaces.
As a true workhorse annual, Lobularia maritima ‘Snow Crystals’ offers fantastic performance even in less-than-ideal conditions, tolerating dry soils once established. Its spreading mounds create a soft, mounding effect ideal for softening hard edges in borders and rock gardens. Gardeners appreciate the reliability of sweet alyssum for filling gaps and providing continuous color.
The specific cultivar Lobularia maritima ‘Snow Crystals’ is recognized for its tetraploid vigor, featuring larger flowers and superior heat and wind tolerance compared to older types. This makes the white mounds of sweet alyssum a dependable choice for season-long embellishment.
Fast Facts
- Plant Family: Brassicaceae
- Plant Type: Herbaceous perennial
- Hardiness Zones: USDA Zones 5-9
- Size at Maturity:
- Height: 0.25-0.75 ft
- Spread: 0.5-1 ft
- Bloom Time: April to June
- Bloom Description: White
- Sun Exposure: Full sun to part shade
- Water Needs: Dry to medium
- Maintenance Level: Medium
How to Grow
Sweet alyssum is easily grown directly from seed into average, well-drained soils. For the earliest spring display, sow seeds indoors about 5 to 6 weeks before your expected last frost date and transplant the seedlings out just before that date. Alternatively, direct sow seeds outdoors several weeks prior to the last frost. Lobularia maritima ‘Snow Crystals’ thrives best with full sun, though it benefits from some afternoon shade in regions experiencing very hot summers, like the St. Louis area.
Watering requirements are flexible; while it prefers medium moisture, this plant notably tolerates dryish soils, fitting beautifully into drought-tolerant landscapes once established. Fertilize sparingly, as excessive richness can lead to excessive foliage growth at the expense of flowers. The key to continuous bloom is timely shearing.
To maintain the dense carpet look and encourage a persistent second flush of bloom, shear the established plants back by about one-half immediately following the initial heavy bloom cycle. In areas experiencing extreme summer heat, flowering may slow down; cutting the plants back helps them recover and prepare for renewed blooming as cooler fall temperatures return. Sowing new seed in August can establish plants for excellent fall color.
Landscape Uses
Sweet alyssum excels in applications where a low, spreading, white border is desired. Use mass plantings of Lobularia maritima ‘Snow Crystals’ along the front of perennial borders to create a softening edge that contrasts beautifully with taller specimens. They are spectacular tucked into rock gardens, where their low profile and tolerance for well-drained conditions mimic their native coastal habits.
For mixed containers, sweet alyssum functions perfectly as a “spiller,” cascading gently over the edges of pots and softening the lines of upright thrillers or mounding fillers. The continuous, cloud-like white flowers of the sweet alyssum provide a bright, neutral base that complements virtually any companion color palette, from hot annuals to cool foliage plants.
Standout Features
Flower Qualities
- Showy
- Fragrant
Noteworthy Characteristics
Lobularia maritima, commonly called sweet alyssum, is one of the easiest annuals to grow. It is a mat-forming plant that produces spreading mounds of well-branched stems clad with linear, lance-shaped, gray-green leaves (to 1” long). Dense clusters of sweetly fragrant, tiny, white 4-petaled flowers cover the foliage mounds from spring to early summer. ‘Snow Crystals’ was the first tetraploid sweet alyssum and has lots of vigor; it is known for its greater heat and wind tolerance, larger flower size, and longer staying power, with white blooms covering 8-10 inch mounds from June to frost.
Tolerances
- Drought
- Dry Soil
Potential Problems
This plant generally experiences no serious insect or disease problems, making it quite robust for an annual bedding plant. Gardeners should be aware that damping off can occasionally affect very young seedlings if conditions are too wet or crowded immediately after sowing. Ensure good air circulation and avoid overwatering seedlings to prevent this fungal issue.
Frequently Asked Questions
What hardiness zones is Sweet alyssum suitable for?
Lobularia maritima ‘Snow Crystals’ is reliably hardy in USDA Zones 5 through 9 as an annual.
How large does Lobularia maritima ‘Snow Crystals’ grow?
This variety typically reaches heights between 0.25 to 0.75 feet, spreading outward to between 0.5 and 1 foot wide.
When does Sweet alyssum bloom?
It produces its distinctive white flowers from early spring, generally starting around April, and continues blooming through June, often persisting later in cooler summers.
What sun exposure does Sweet alyssum need?
For best results and consistent flowering, plant sweet alyssum where it receives full sun to part shade; afternoon shade is beneficial in very hot climates.
Conclusion
The inclusion of Lobularia maritima ‘Snow Crystals’ guarantees a season-long display of fragrant, attractive white blooms, coupled with surprising tolerance for drier conditions. Its vigorous nature makes it a top choice for low maintenance bedding and edging across USDA Zones 5-9. Plan to incorporate sweet alyssum into your spring planting schedule to enjoy its carpet of fragrance immediately after the threat of frost has passed.
Companion Planting
When designing with sweet alyssum, consider its compact size and preference for well-drained soil. It serves as an excellent foreground plant for upright summer bloomers such as Salvia, tall Zinnias, or standard-sized Geraniums, offering a fragrant, low transition to hardscape elements. Its white coloration pairs beautifully with vivid purples or deep blues used in mixed beds, allowing those colors to pop without clashing.
Because sweet alyssum thrives in conditions that are not overly rich or constantly wet, it pairs well with Mediterranean herbs like Thyme or Oregano, which share a similar tolerance for drier, sunnier sites. Avoid planting Lobularia maritima ‘Snow Crystals’ directly next to heavy feeders that require consistent moisture, as this can cause the alyssum to decline prematurely or become leggy.
Wildlife Benefits
The tiny, highly visible white flowers of Lobularia maritima ‘Snow Crystals’ are irresistible to many beneficial small insects. While popular lore often focuses on butterflies, the flower structure is particularly attractive to minute pollinators, including beneficial parasitic wasps and hoverflies, which are excellent aphid predators. Planting drifts of sweet alyssum helps create a welcoming micro-environment that supports garden health.
The dense clusters of bloom provide easily accessible nectar sources early in the season, a crucial time when other nectar resources may still be emerging or slow to develop. By ensuring you shear the plants after the initial flush, you encourage subsequent blooms, thus extending the availability of this important food source for your local beneficial insect populations throughout the growing season.
