Lobularia maritima, commonly known as sweet alyssum, is an annual flowering plant that grows very low and has a tendency to spread its branches over the soil, creating a mat. That is why this lovely ornamental is an excellent choice for a groundcover or a bedding plant.
I. Appearance and CharacteristicsÂ
Lobularia maritima (syn. Alyssum maritimum) is a species of low-growing flowering plant in the family Brassicaceae. Its common name is sweet alyssum or sweet alison, also commonly referred to as just alyssum (from the genus Alyssum in which it was formerly classified).
The genus name Lobularia comes from a Greek word meaning ‘small pod,’ referring to the shape of the fruits; the obsolete Alyssum can be translated as ‘lack of madness,’ referencing the historical use of the herb as a treatment against rabies. The name of the species maritima refers to its preferred coastal habitat.
This plant is native to the Mediterranean Basin and the Macaronesia region: (Canary Islands, Madeira, Cape Verde). It is widely naturalized elsewhere in the temperate world, including the United States. There is an endemic subspecies in the local flora of the Columbretes Islands of the western Mediterranean.
Lobularia maritima is an annual plant (rarely a short-lived perennial plant) growing to 5–30 cm (2–12 in) tall by 20–30 cm (8–12 in) broad. The stem is very branched, with dense clusters of small flowers. The leaves are 1–4 cm long and 3–5 mm, broad, alternate, sessile, quite hairy, oval to lanceolate, with an entire margin.
The flowers are about 5 millimetres (0.20 in) in diameter, sweet-smelling, with an aroma similar to that of honey, with four white rounded petals (or pink, rose-red, violet. yellow and lilac) and four sepals. The six stamens have yellow anthers. The flowers are produced throughout the growing season, or year-round in areas free of frost. They are pollinated by insects (entomophily) as its sweet honey-like fragrance is attractive to bees, flower flies, stingless wasps and butterflies. The fruits are numerous elongated seedpods rather hairy, oval to rounded, each containing two seeds. The dispersal of seed is affected by the wind (anemochory).
Lobularia maritima is cultivated in gardens, with many horticultural varieties with purple or pink flowers. The plant is best planted in early spring, but requires little maintenance when growing. Although an annual, it may reseed in temperate climates. It will flower more profusely if spent blooms are trimmed. When grown in gardens, it is typically used as groundcover, as it rarely grows higher than 20 cm (8 in) tall. It is also grown in cracks in paving and walls, and is especially associated with coastal locations. It prefers partial shade, and is resistant to heat and drought. Plants with darker-colored flowers do better in cooler temperatures. Lobularia maritima has high drought and heat resistance.
II. How to Grow and Care
Sunlight
Sweet alyssum loves full sun, but it does not like prolonged dry periods. If your region is sweltering and dry, an area with afternoon shade will work best for this plant. Aim to plant your sweet alyssum somewhere where it can get six to eight hours of sunlight a day.
Temperature and Humidity
Gardeners can grow sweet alyssum in temperate weather all year long, although the plants are short-lived. Typically, they are vigorous self-seeders, however, hybrid varieties may not look like the parent plant. So, it may seem that the same plants are surviving all year long; the reality is that new seedlings are filling in.
Although many varieties may stop flowering in heat, sweet alyssum plants repeat bloom. They will likely pick up again in the fall. In high humidity, compensate by reducing the amount of water given to plants.
Watering
Provide your sweet alyssum plants with at least an inch of water every week, watering them more frequently during hot weather days or dry spells. The water should drain well. If you plant your sweet alyssum in a stony landscape (or anywhere that dries out quickly), provide extra water.
Soil
Sweet alyssum plants prefer soil that is moist and well-draining. They’re tolerant of many different planting locations and on sandy beaches and dunes. It can also grow on cultivated fields, walls, slopes, and even in cracks in sidewalks or walls. The plants will do poorly in boggy soil or where drainage is problematic.
Fertilizing
If grown in your garden, sweet alyssum will not need additional feeding, unless your soil is nutrient-poor. However, some additional nourishment is encouraged for fast growth and nice blooms. If grown in a container, it will need more regular watering and feeding. Add some liquid, balanced fertilizer every two to three weeks, especially during bloom periods. Also, when planting, mix some organic compost or slow-release fertilizer with the planting soil to give it an additional sprout boost.
Pruning
Regular removal of dead or spent flowers from living plants can ensure vivid and fragrant flowers of sweet alyssum throughout the blooming season. As it can grow tightly and compact, prune off one third to half of the growth when flowers fade, or they become leggy. Also, remember to always disinfect your pruning tools at the beginning, the end, and if possible, between the cuts. In this way, you will minimize any chance of cross-contamination from any unnoticed pathogens.
Propagation
It is best to grow this fast-growing plant in the early spring. It proliferates from seed. You can start the seeds indoors before the last frost and transplant them outdoors after the threat of frost has passed. Alyssum is somewhat frost-tolerant once established, but tender transplants are not hardy enough for frost.
- Or you can direct sow the seeds outdoors as soon as the soil has thawed and can be worked. This plant is considered a great filler or edger plant, filling in areas where you want to fill in bare patches of soil alongside other plants. This low-growing, carpet-forming plant is not usually propagated by any other method.
- How to Grow Sweet Alyssum From Seed
- You can start sweet alyssum from seed or directly transplant it into your garden from nursery flats; both are widely available. To start from seed, scatter the seeds on top of the soil and press them down lightly, so they make good contact with the soil and remain exposed to light. Keep the soil moist until germination; water whenever the soil feels dry.
Potting and RepottingÂ
Sweet alyssum grows well in containers. When growing in containers, use good quality potting soil and ensure there are drainage holes in the bottom of the pot for excess water to seep out. It’s favored for hanging baskets or window boxes, alone or as a companion to petunias and other similar-care plants.
If transplanting, fill the container with soil, dig out a hole the size of the existing root ball, put the root ball in the hole, and fill the soil around it. Leave at least two inches between the soil line and the container’s rim.
Overwintering
To overwinter alyssum, cut it down in winter, cover it with frost cloth, or take containers inside. You can also leave it untouched. It’s a prolific self-seeder, so in late winter or early spring, as the ground begins to thaw, you can cut away the dead brush to make way for the seeds left behind from the previous growing season.
Pests and Diseases
Common Pests & Plant Diseases
Sweet alyssum is subject to downy mildew, stem and crown rot, or general decline due to poorly draining soil. It’s key to prevent overwatering with these plants.
Butterflies, pollinators, and songbirds are drawn to sweet alyssum, but they really have serious problems with other pests and diseases.
Common ProblemsÂ
This plant can grow invasively in warmer climates—not needing much of anything to proliferate well on its own in those areas. However, growing outside of those areas can be more difficult. These conditions include the heat index, frost or freezing temps, excessive water, poor drainage, poor soil, or not enough light.
Wilting Flowers and Foliage
If you haven’t planted alyssum in well-drained soil or if it’s very hot, it could wilt. Alyssum does not tolerate intense heat well. Some cultivars have been developed to tolerate hot temperatures without wilting, although the most common types will shrink during the height of summer. You can counterbalance the heat with water, but ensure the soil drains well and efficiently.
Bottom line: You should expect wilting. It may rebound in the fall when the temperatures level out some. You can also cut down the wilted plant by one-third, water it, and feed it a water-soluble fertilizer to encourage new growth.
Curling Flowers and Leaves
If you notice curling flowers and foliage, inspect under the leaves and flower petals for mini sap-sucking cyclamen mites. They are hardly visible to the naked eye, appearing like tiny oval spiders if you have a magnifying glass handy. Apply neem oil or insecticidal soap to rid your plant of an infestation.
Yellowing Leaves
If you notice your plant’s leaves beginning to yellow, a spike in temperatures can be the cause; either that, transplant shock, lack of water, or poor soil nutrients. Once a plant’s leaves turn yellow, that leaf is dying. One leaf or several yellow leaves is a warning sign and not necessarily a death sentence for the entire plant.
Try to isolate the cause and remedy the growing condition. Once the entire plant wilts, then flowers and foliage are dead. Cut back the plant and wait for more temperate climates or more favorable growing conditions for sweet alyssum to grow back.
III. Uses and BenefitsÂ
- Ornamental uses
Sweet alyssum is a mat-forming plant that does well as a seasonal ground cover. It is popular as an edging plant in walkways and its height makes it a good accent plant in rock gardens. Its fragrant flowers attract pollinators and birds. Vibrant companion plants of the sweet alyssum include the Autumn Joy Herbstfreude, Black Adder or Blue Fortune Giant Hyssop, and David Howard Dahlia. For more muted tones, drought-resistant Feathertop Grass makes a great accompaniment.
- Culinary uses
The petals, leaves, and tender stems of the plant can be eaten raw or cooked.
IV. Types of Sweet Alyssum
There are several common varieties of sweet alyssum:
- ‘Easter Bonnet’: An early blooming type, typically found in lavender or white
- ‘New Carpet of Snow’: A low-growing variety, covered in petite white flowers
- ‘Pastel Carpet’: A varietal whose blooms blend pink, lavender, and cream
- ‘Snow Crystals’: A tidy, mounding variety with translucent white flowers
- ‘Snow Princess’: Vigorous variety that’s heat tolerant with white flowers; intensely fragrant; grows up to six inches tall and five feet long
