Lobularia - Sweet Alyssum: Sowing, Planting, and Growing

Botany and description

The Lobularia maritima (syn. Alyssum maritimum) or Sweet alyssum, also known as Seaside alyssum, is an annual plant belonging to the Brassicaceae family (formerly known as Cruciferae). The genus Lobularia includes 5 species, some perennial, others annual: Lobularia maritima is the most commonly cultivated in our gardens. The type species has white flowers and grey foliage, earning it the nickname “Silver Basket”. There are many horticultural varieties, sometimes more compact or with other flower colours (pink, purple, crimson…).

Alyssum maritimum, botanical plate from 1896

The Lobularia maritima is a plant native to the Mediterranean basin. However, this plant has naturalised in other parts of the world: in the Bay of Biscay, along the coast, and even in California. It thrives among rocks, in sandy soil, but can occasionally be found on slopes or wastelands with calcareous soil. Although Lobularia is cultivated as an annual, it is not uncommon to find self-sown plants in the most unexpected places: rockeries, borders, paving, walls, and even in pots, thus perpetuating the plant.

Sweet alyssum is a plant that grows in small clumps up to 30 cm tall, highly branched. The base of the clumps is slightly woody. The foliage is alternate and sessile, with a glaucous colour and grey undersides. The leaves are typically villous, simple, and narrow.

The flowering period is very long and can extend from March to October in mild climates, starting from June further north. The inflorescence begins as a rounded raceme (a type of flower cluster) that elongates over the months. Each flower, 3 to 4 mm in diameter, reveals 4 sepals, 4 rounded petals (typical of the family!), and 6 stamens with yellow anthers. The flowering is particularly fragrant, with a scent reminiscent of honey sweets. Pollination is entomophilous, carried out by insects, which are numerous and attracted to the sweet alyssum flowers.

Sweet alyssum in white and mauve. On the right, a close-up of the flower

The infructescence is elongated and bears numerous villous siliculas (small siliquas, typical of Brassicaceae). Each silicula contains two seeds. Seed dispersal is anemochoric, with the seeds being carried by the wind.

The caterpillar of the Iberian Pierid (Pieris mannii) feeds on the foliage of Sweet alyssum. In fact, lobularias are used in the United States in cabbage fields to attract Pierid caterpillars. This is an organic and natural way to divert pests to another plant.

As the plant grows quickly and covers the ground rapidly, agronomic research is underway to use lobularias as ground cover in fields. Not to mention that the flowering attracts a large number of pollinating insects. Consider this for your own vegetable garden!

Our most beautiful varieties

The sweet alyssum or Lobularia maritima is the most cultivated species of the genus in our region. It has been declinated into numerous varieties: with pink, mauve, or violet flowering; or sometimes more compact. Here are our favourites:

Lobularia Snow Princess

The Alyssum Snow Princess, also known as Lobularia, is a vigorous annual plant with a creeping habit. From the beginning of the season, it forms a tapetum of small flowers, 2 to 8 cm in diameter, gathered in clusters of fragrant white blooms.

• Flowering time August to November
• Height at maturity 40 cm

See the product sheet

Lobularia maritima Princess in Purple - Sweet Alyssum

The sweet alyssum 'Princess in Purple' is a vigorous annual plant with a creeping habit. Highly floriferous, it produces a tapetum of small flowers, 2 to 8 cm in diameter, gathered in clusters of fragrant lavender to deep purple blooms from the start of the season.

• Flowering time August to November
• Height at maturity 40 cm

See the product sheet

Lobularia maritima Snow Crystals

The Alyssum 'Snow Crystals' forms very uniform snowy tapetums, as its immaculate flowers are particularly large and perfectly cover its compact foliage. It quickly forms dense, spreading cushions that work wonders in borders, as well as in hanging baskets and flowering containers.

• Flowering time June to September
• Height at maturity 15 cm

See the product sheet

Sweet Alyssum Rosie ODay

The Lobularia maritima procumbens or Alyssum Rosie'O'Day is a lovely variety of sweet alyssum with fragrant pink blooms. This small annual plant with a spreading habit forms dense, fragrant cushions in just one year, perfect for rockeries and flowering containers.

• Flowering time July to October
• Height at maturity 12 cm

See the product sheet

Lobularia maritima Royal Carpet

This Lobularia maritima or sweet alyssum 'Royal Carpet' is an annual ground cover plant with very attractive flowering. Indeed, its numerous small violet-purple flowers appear from June and continue to bloom until October. They are abundant, fragrant, and attract many insects.

• Flowering time July to November
• Height at maturity 15 cm

See the product sheet

If you can’t decide on the colour of your alyssums, there are also mixes available.

Sweet Alyssum Magic Circles Mix

This mix of Lobularia maritima or dwarf Alyssum Magic Circles is a collection of annual ground cover plants with very attractive flowering. Indeed, the numerous small flowers in varied colours appear from June and continue to bloom until October.

• Flowering time July to November
• Height at maturity 15 cm

See the product sheet

Planting alyssums

Where to Plant?

Lobularias thrive in sunny spots but can tolerate partial shade. The soil should be light and well-draining, preferably alkaline to neutral. They will do well in ordinary, rocky, or sandy soil, even very dry. Excessive moisture will cause them to wither. Sweet alyssum can grow in very little soil.

Like gold dust (Alyssum sp.), sweet alyssum makes an excellent ground cover for slightly dry areas (such as a sunny slope) where other plants struggle to establish. It can be used to brighten up a rock garden or sun-baked flower beds, or as a border for a sunny flower bed. Sweet alyssum can also be tucked into the top of a dry stone wall or nestled between paving stones or in the crevices of walls.

Note that lobularias also thrive in pots, planters, or hanging baskets on sunny balconies and terraces.

Lobularia or sweet alyssum

When to Plant?

Lobularia plug plants can be planted in spring (ideally from March to May), up to early summer, either in the ground or in containers. Sowing is done in spring, but can also be attempted in autumn in mild climates.

How to Plant?

In the Ground

• By sowing, prepare the soil carefully: weed, loosen well, and lighten with a bit of compost if needed. Rake the soil smooth and sow thinly by scattering. Cover with a little compost and water gently. Continue watering, without overdoing it, for at least two months after sowing. Thin out the young plants if necessary if sown too densely;
• By planting small buckets or plug plants: dig a hole twice the size of the root ball. Loosen the soil well and add some compost, or even a few gravels, if it’s too heavy. Plant your sweet alyssum and fill the hole with the excavated soil, but without burying the collar. Lightly firm the soil around the base with your hands. Water thoroughly to avoid any air pockets between the soil and the roots.

Allow for 5 to 7 sweet alyssum plants per square metre!

In Pots

• Spread a good layer of drainage (gravel or clay pebbles) at the bottom of the container, which must have one or more drainage holes;
• Plant the bucket in a mix of ordinary soil, Mediterranean plant compost, and coarse sand;
• Water to encourage establishment, then once every two weeks;
• Place your pots in full sun.

Sweet alyssum planted in a pot

Maintenance, Pruning, and Care for Lobularia

Watering

Lobularias are very drought-tolerant. You can therefore forget about watering once flowering begins in spring and when the plant covers the soil well.

In pots, allow the surface of the substrate to dry out between waterings.

Pruning

Don’t hesitate to give a quick trim with garden shears or scissors to the clusters of faded flowers. This will encourage the plant to produce more flowers and thus prolong the flowering period.

You can also pinch the young shoots in spring to help the young plant become more ramified.

Fertiliser

In pots only, alyssums can be given a liquid fertiliser for flowering plants every 3 to 4 weeks.

In open ground, avoid enriching your soil for alyssums. Indeed, the plant may produce foliage at the expense of flowering.

Possible diseases and pests

Young Lobularia plants attract slugs and snails early in the season. Keep an eye on your sweet alyssums planted in the ground.

The plant also harbours insects: cabbage white caterpillars, aphids, thrips… without being significantly affected. In the case of a severe aphid infestation, you can spray water mixed with black soap.

In hot and humid weather, alyssums are sometimes prone to powdery mildew (white spots or patches) or downy mildew (rust-coloured pustules). However, this rarely happens and mainly in poorly drained soil. Prune the affected parts and avoid watering the foliage. To prevent and combat powdery mildew, follow our advice: “Powdery mildew or white mould: prevention and treatment”.

How to propagate your alyssums?

The simplest method remains sowing. In fact, the plant often takes care of reseeding itself in the most unexpected places in the garden: between paving stones or rocks, for example.

By sowing directly in the ground in spring

• Prepare the soil carefully: weed, loosen well, and lighten with a bit of compost if needed;
• Smooth the soil with a rake and sow thinly by scattering;
• Cover with a little compost and water gently;
• Continue watering, without overdoing it, for at least two months after sowing;
• Thin out the young plants if necessary, spacing them 20 cm apart, if you’ve sown too densely.

By sowing in a seed tray, under a cold frame (protected from frost) at the end of winter:

• Sow thinly in well-sifted seed compost;
• Cover with a little compost and water gently;
• Continue watering, without overdoing it;
• After two months, you can transplant them into pots or directly into the ground.

Here are a few ideas for plant combinations:

The Silver Basket is unparalleled for greening a neglected spot in the garden, whether deemed too dry or on overly poor soil.

In a dry or gravel garden, the Sweet Alyssum adds pep with its flowers, which range from white to mauve or violet. The Lobularia works wonders on slopes, in dry rockeries, sun-baked flower beds, and even in pots on the terrace.

Sweet Alyssum pairs easily with other rockery perennial plants: for example, alyssums or Golden Baskets, but also aubrietas, ageratums, or even rock campanulas.

It loves to be surrounded by Mediterranean perennial plants, all as undemanding as itself: santonias, artemisias, nepetas, echinops, eryngiums, lamb’s ears, helianthemums… not forgetting southern bushes like lavenders, rosemary, bushy sages…

In a rockery, a beautiful combination of sweet alyssum, ageratum, artemisia, and aubrieta