How to Grow and Care for Sweet Alyssum

Sweet alyssum makes a colorful carpet of tiny flowers to blanket your garden or landscape. Within two months of being started from seed, this plant quickly covers the ground with tiny cross-shaped, four-petal flowers. Its gray-green leaves are slightly hairy, narrow, and lance-shaped.

Easy to grow from plant or seed, sweet alyssum is a cool-season flower native to Europe that is set out in early spring once all danger of frost has passed (in frost-free climates, sweet alyssum can also be grown throughout the fall and winter). Most varieties will fade in the heat but bloom again in the fall.

As sweet alyssum plants spread, they create a living mulch under taller plants. Use sweet alyssum along edges in the garden or fill nooks and crannies on walkways and walls. The tight, free-flowering plants are also great "spillers" for hanging baskets and containers.

Sweet Alyssum Care

Here are the main care requirements for growing sweet alyssum:

• Plant in well-draining soil.
• Place in an area with full sun but that also allows for shade.
• Provide your sweet alyssum plants with an inch of water every week, and water more when the climate becomes dry.
• Deadhead the plant to encourage more blooms.

Light

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 where it receives six to eight hours of sunlight a day.

Soil

Sweet alyssum plants prefer soil that is moist and well-draining. They're tolerant of many different planting locations, including sandy beaches and dunes. You'll find the plants even in locations without much soil, such as walls, slopes, or cracks in sidewalks. In boggy soil or insufficient drainage, on the other hand, the plant will do poorly.

Water

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.

Temperature and Humidity

Gardeners can grow sweet alyssum in temperate climates all year long, although the plants are short-lived. Alyssum is somewhat frost-tolerant once established, but tender transplants are not hardy enough for frost.

Fertilizer

Typically, in-ground sweet alyssum plants do not need fertilizer unless the soil is poor. Plants grown in containers will need monthly feedings using a water-soluble, well-balanced fertilizer. When starting seeds, add a time-release fertilizer to the soil at planting. When blooms are spent, apply again to stimulate new growth. Too much fertilizer tends to cause lush foliage and reduced blooms.

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 6 inches tall and 5 feet long
• 'Royal Carpet': With a height of only 3 inches and rich purple-violet flowers, this variety lives up to its name.

Pruning

Deadheading sweet alyssum will keep the plants flowering and set new buds quickly. If you have a significant drift of plants, shearing them by one-third is an easier option than deadheading. Some varieties will readily re-seed themselves. The plants tend to become leggy and gangly, so pruning will keep the plants looking trim and neat.

How to Grow Sweet Alyssum From Seed

Alyssum is widely available as nursery flats but you can also propagate it by starting it from seed in the early spring. Either start the seeds indoors before the last frost or direct sow the seeds outdoors as soon as the soil is ready to be worked.

1. 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—they need light to germinate.
2. Keep the soil moist until germination and water whenever the soil feels dry.
3. If starting the seeds indoors, transplant them outdoors after the threat of frost has passed.

Typically, sweet alyssum is a vigorous self-seeder, however, hybrid varieties may not look like the parent plant.

Potting and Repotting Sweet Alyssum

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 container-grown plants inside. Alternatively, leave it untouched. It's a prolific self-seeder, so in late winter or early spring, as the ground begins to thaw, cut away the dead foliage to make room for the seeds from the previous growing season to land on the soil and germinate.

Common Pests & Plant Diseases

Sweet alyssum is generally problem-free, although aphids will arrive on the scene when the plant is under stress.

Sweet alyssum may suffer from downy mildew, stem and crown rot, or general decline due to poorly draining soil. It's key to prevent overwatering with these plants.

How to Get Sweet Alyssum to Bloom

Sweet alyssum blooms in the early spring and then again in the fall, as it grows best in cooler temperatures.

Bloom Months

June to October are the best months to see sweet alyssum in full bloom.

How Long Does Sweet Alyssum Bloom?

It takes about two months for a seed to germinate, grow, and bloom. In certain regions, it will bloom all summer. Although many varieties may stop flowering in heat, sweet alyssum plants bloom repeatedly. They will likely pick up again in the fall.

What Do Sweet Alyssum's Flowers Look and Smell Like?

Sweet alyssum, as its name suggests, has a sweet aroma, much like honey (although the plant is related to cabbage and mustard). Its tiny flowers grow together in close clusters and are white, pink, and purple. They will self-sow and provide bright colors year after year in milder climates.

How to Encourage More Blooms

Applying a water-soluble fertilizer is the best way to encourage new growth when the blooms appear.

Deadheading Sweet Alyssum Flowers

Deadheading sweet alyssum will keep the plants flowering and set new buds quickly. If you don't want to deadhead them completely, cut the plant back by half during the summer, which will stimulate new growth.

Common Problems With Sweet Alyssum

This plant usually grows aggressively in warmer climates—not needing much of anything to proliferate well on its own in those areas. However, growing rampantly outside of ideal conditions is more difficult. These conditions include the heat index, frost or freezing temperatures, 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. Give the plant extra water, but ensure the soil drains well and efficiently.

In hot weather, you should expect wilting. The plant may rebound in the fall when the temperatures drop. If you don't want to wait, 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

There are many different possible causes for yellowing leaves: a spike in temperatures. transplant shock, lack of water, or poor soil nutrients. Try to identify the cause as early as possible before the entire plant is affected. Often, the remedy consists of cutting back the plant and waiting for more favorable temperatures in which sweet alyssum restarts its growth.