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Alyssum

Karin Heimberger-Preisler Karin Heimberger-Preisler

Alyssum is best known in rock gardens. We reveal what else the Alyssum genus has to offer, and provide you with planting and care tips.

Origin

Alyssum originates from central and southern Europe and Asia Minor and belongs to the cruciferous plant family (Brassicaceae). In nature, the representatives of this genus inhabit steppes and rock crevices. However, there are several species which are suitable for cultivation in the garden and cut a good figure as sun-worshipping cushion shrubs in rock gardens or on gravel surfaces. They are very similar in appearance and growth behavior and form luxurious, blooming flower carpets which are valuable bee meadows.

Appearance and Growth

Alyssum grows as a persistent shrub or half shrub and keeps most of its leaves in the winter. It has a cushion shaped growth and reaches heights of 7.87 to 16 inches. The initially upright growing shoots soon nod towards the soil during the flowering period and appear extremely graceful lying on gravel and stones. The small-leaved Alpine Alyssum (Alyssum serpyllifolium) only grows 3.94 inches tall. The narrow, spatulate leaves of all species of Alyssum are silver-gray and disappear in the flowering period under a yellow carpet of flowers. Their flowering period is between April and June. Tiny, four-petal flowers are typical for cruciferous plants; they sit together in dense bunches with vibrant yellow tones and generally exude a delightful honey fragrance.

Location and Soil

Alyssum requires lots of sunlight to thrive as well as dry, highly permeable soil. A humus, sandy, loamy soil which is calciferous and low in nutrients is ideal. Heavy soils are unsuitable and must be made more permeable with an admixture of sand or gravel. The Alyssum is a professional faster and even thrives in small cracks, step alcoves and on dry stone walls.

Dry stone wall with Alyssum

During the flowering period, dry stone walls disappear almost completely under the yellow Alyssum flowers

Planting

The best time to plant Alyssum is in the spring or fall. Calculate around nine plants per square yard and plant at a distance of about 12 inches from each other.

Care Tips

The stem is woody at the base of the Alyssum and tends to be bare. Retain its compact shape by cutting back the half shrub in the fall by about a third of its growth height. Light fertilizing promotes vitality in older plants. However, avoid too many nutrients, so that the abundance of flowers does not suffer due to increased shoot growth. Alyssum species form a deep-reaching tap root, making it difficult to transplant or divide them.

Overwintering

Alyssum is fully winter-hardy and, provided you choose a permeable substrate, waterlogging will also not pose a problem throughout the winter months.

Utilization

As a typical rock garden plant, Alyssum is at home in dry stone walls, rock crevices, step alcoves and the joints between step plates. Flat planting troughs are also ideal for planting. Pretty partners are equally cushion-shape growing Aubrieta, moss phlox, rockcress or white candytuft. Red tulips add a colorful accent to the yellow Alyssum flowers, as do blue and violet Bart-Iris. Alyssum is a valuable partner on gravel areas, as its early flowering is very important for nectar-seeking bees.

Alyssum and Aubretia

Aubrieta and Alyssum are not just a perfect color match, they also have similar location requirements

Important Species and Varieties

Silver Alyssum (Alyssum argenteum) has compact, meadow-like growth, Mountain Alyssum (Alyssum montanum) forms loose flower bunches in an intensive golden-yellow, it is particularly known in the variety ‘Basket of Gold’. The species Alyssum wulfenianum is also known as a Mountain Alyssum. Its luxurious, golden-yellow flowers only appear in May. If you cut back the flowers there will often be a second bloom. Mountain Alyssum (Alyssum saxatile) is more frequently referred to as Aurinia saxatilis. The commercially available varieties of this are ‘Compactum’, with golden-yellow flowers, and ‘Citrinum’, with sulfur yellow flowers. The variety Alyssum saxatile ‘Plenum’ has double-flowers. The tiny-flowered alpine Alyssum (Alyssum serpyllifolium) forms low, gray foliage mats.

Propagation

Alyssum can be propagated through seeds. Ideally, pre-culture should begin in March. Do not cover the fine seeds after sowing, rather gently push them in. Even moisture is also important for germination. The young plants should then be planted in the desired location in the fall. Propagation through cuttings is also possible. For this, take base cuttings, that is saplings which appear directly next to the main shoots, in early summer and then plant these in compost.

Diseases and Pests

The robust, long-living Alyssum is not at all susceptible to plant diseases and pests, even snails avoid these plants.

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