Allium (Ornamental Onion) – Plant Care and Bloom Time

Ornamental onion is a beautiful and versatile flower and will adorn any garden or plot with its bright, globular inflorescences. The allium is a natural bulbous plant that begins to bloom in late spring and early summer and stays at its peak of beauty for a long time. After flowering and during the seed ripening period, the withered heads of ornamental allium onions will look quite spectacular.

The leaves are linear or strap-shaped. Each flower of the ornamental onion is relatively tiny, and the flowers are combined into an inflorescence, which gives the allium its main decorative character. The inflorescence balls of some varieties of ornamental onion reach up to 30 cm in diameter. Most ornamental onions flower in May and June, but there are also autumn-flowering allium varieties. Some varieties bloom for a long time and retain their attractive appearance even after finishing.

The ornamental onion requires attention from the gardener. It prefers a sunny or semi-shady location and grows readily in ordinary, moderately fertile, light soils. The main requirement for ornamental onions is good soil water permeability (if water stagnates, the onion bulbs will rot). Allium is drought-resistant; the frost resistance of many species depends on climate zone 3. Tall varieties of ornamental onion need protection from the wind during flowering.

Growing Ornamental Onions

Once you have decided on the area you want to grow your allium, you will need to dig it out and add mineral fertilizer and humus to the soil. Then prepare the planting holes and irrigate them with a bit of water. Once the ornamental onion has been planted, cover the plot's surface with mulch.

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Planting in the loose soil is carried out at the end of September, with the temperature of the earth in the area of root system formation should be about 10 degrees.


Growing a culture on your garden plot is simple enough because it is unpretentious in care. The property should be promptly removed from the weeds; its surface should be regularly loosened and covered with a layer of mulch during the vegetation period. Water the allium in moderation; it is one of those plants that tolerate a brief drought better than stagnant water.

Site Selection

A sunny location is best for it as it is a hellebore. The soil should be loose and porous. To prevent stagnant liquid in the root system, you should improve the drainage properties of the earth. A suitable soil should have a pH close to 7.0. Lowlands and areas where water stagnates during snowmelt and rainfall are unsuitable for cultivating ornamental onions. Prepare a hole 2 or 3 times the bulb's height for planting so the root system will be protected from drying out and from winter frosts.

Should the Bulbs be Dug up For the Winter?

Specialists advise digging up the bulbs annually after the seeds have fully matured and the leaves have dried. Store the bulbs where the temperature does not exceed 18-20 degrees. Some species can be grown in autumn and spring. Put small bulbs in a container with peat or sawdust for storage to prevent them from drying out.


Allium can be given plenty of nutrients, such as wood ash and compost. The plant needs fertilizer during active leaf growth and when the buds are being formed, and the bulbs are forming. To make it survive the winter better, in the early autumn, fertilize it with potassium and phosphorus and place undissolved granules in the soil. Only seedlings in the initial growth stage can be transplanted.

Propagating the Allium By Seed

Alliums grown from seed will not start to flower until several years later. For example, the yellow and blue alliums will bloom in their third year, and those with huge flowers (such as the Schubert, Christoph, and Hyganthus) will flower in the sixth or seventh year after sowing.

The seeds of Giant Allium are recommended for cold stratification, but Allium germinates well in a warm place. If conditions are ideal for the growth of ornamental onions, they can be successfully propagated by self-sowing.

Types of Ornamental Onion

  • Allium aflatunum

    This species can reach a height of up to 150 centimeters and a diameter of up to 12 centimeters. The dense, umbrella-shaped inflorescences consist of pale purple, star-shaped flowers. This plant is straightforward to care for and looks striking and unusual during flowering.

  • Allium gladiator

    This species and the simple edible onion are very close relatives. The dark green foliage can be used as food if desired. The shrub can reach a height of about 100 centimeters. The star-shaped flowers are blue-lavender, have six petals, and a slightly sweet, pleasant scent. The inflorescences are 20 centimeters across or even larger. This species looks great in alpinaries and stony gardens and goes well with bearded irises.

  • Allium eros

    This plant's beautiful globular inflorescences can vary in color from pale lilac to pink. The shrub's height varies from 0.3 to 0.35m, with flowers about 10 centimeters across. It blooms in June.

  • Round-headed allium

    This species blooms relatively late in mid-summer and the flowering time is about 4 weeks. The inflorescences are oval, and the flowers are pink or mauve. Stems can grow to a height of approximately 0.6 m.

  • Allium blue

    This species is one of the most decorative allium species. The stems can grow to a height of about 0.8 m. The inflorescence reaches about 70 mm across, forming a lush umbrella with a semi-spherical or rounded shape. One inflorescence contains 200 to 250 bell-shaped, blue flowers. The color is incredibly showy, and the globe may appear to have the most beautiful blue blooms.

  • Allium moth (yellow onion)

    The shrub height of this species reaches 0.2-0.3 m. The loose inflorescences are made up of star-shaped flowers in a rich golden yellow. It flowers in late May and lasts for around three weeks.

  • Christophe allium

    This species is considered the most decorative of the medium-growing ones. As a rule, the shrub's height does not exceed 0.3-0.4 m. But if the flower has favorable growth conditions, it can grow to a height of up to 0.6 m. Its globular inflorescence is huge and can expand to a width of approximately 25 centimeters. It consists of many small star-shaped flowers, which may appear purple or violet. A spectacular flowering can be seen in June and lasts approximately 30 days.

  • Allium Ostrovsky

    This small, very showy species can reach a height of about 0 2 m. The large, crimson, broad bell-shaped flowers are very pleasantly fragrant. They form part of inflorescences which can grow to around 10 centimeters across.

  • Allium Ivory queen

    This plant is capable of decorating any garden. The stems vary in height from 0.25 to 0.35 m. Beautiful ivory-colored flowers are formed on the branches, which may reach up to 12 centimeters across, and are very colorful and pleasantly scented. But when not flowering, it still looks lovely with its pretty foliage. The leaves are corrugated and have an unusual bluish-green color. Flowering lasts about three weeks.

  • Allium bulgaricum

    This species can grow to a height of about 0.9 meters. It flowers in the early summer weeks with very showy purplish-white flowers in clusters.

  • Allium giganteum

    It is so-called because the plant can grow to approximately 150 centimeters. Its umbrella-shaped inflorescences are about 80 mm across. The star-shaped flowers may be pale purple. The squat, broad leaflets are strap-shaped. Flowering occurs in June and lasts for approximately 3.5 weeks.

  • Allium unifolium

    This plant is native to North America. It is very decorative even though its flowers are not spheres but loose umbrellas. The shrub is at most 20-25 centimeters in height. Because the shrubs are small and compact, they can be used to create neat arrangements in containers, for example.

  • Schubert's allium

    This small shrub can grow to 25 to 30 centimeters with pinkish-grey, star-shaped inflorescences. It will flower in June. It looks nothing like an onion, and only a professional can tell if Shubert's allium is a relative.

  • Allium Kovani

    This is an early flowering plant that blooms in May and June. Its long stems are between 0.3 and 0.4m tall, and the tops form spectacular inflorescences made up of small snow-white flowers up to 40mm across and with a pleasant scent. Flowering lasts 15 to 20 days. If you rub the shoots or leaves, you can smell the garlic.

  • Allium Neapolitanum

    This small shrub can grow to a height of 25 to 35 centimeters. Its broad-bell-shaped pink flowers are 10 to 14 mm long and arranged in a flat or slightly convex umbrella-shaped inflorescence.


Ornamental onions look better in the flowerbed. The brightly colored flowers on tall stems look good in fresh and dry bouquets. When cut, they stay fresh for around two weeks, but the water in the vase must be changed frequently to eliminate the specific onion smell.

Although these plants are considered undemanding, they need proper watering, especially when planted and flowering. Water onions regularly as the soil dries out. It has become popular in garden landscaping because of its lush caps, which open as early as late spring, bloom for a long time, and then produce a seed head that is also quite exquisite in appearance.
Its color palette is quite broad, ranging from snow white to purple. The shape, size, and structure of the inflorescences and leaves make the representatives of this genus very different. The ornamental allium onion will not give you any trouble in cultivation. The plant tolerates drought, and most species can withstand quite severe frosts. It thrives in sunny or semi-shaded locations and requires little or no soil.

This crop's primary need is its good water permeability, as the bulbs will rot if water stagnates. However, appropriate watering is mandatory for the crop, especially at the beginning of the vegetation, when leaves and flower stems are forming. Therefore, it is best to water the Allium when the soil has dried out and always to be guided by the circumstances.


Do ornamental onions need to be dug up?

When growing ornamental species of the genus Allium in a temperate climate zone, it is best to dig out the bulbs annually after the seeds have ripened and the leaves have withered and plant them again in autumn.

Where is the best place to plant Alliums?

Since ornamental onions may not be replanted for several years, choosing the right place to plant them is essential. Alliums are very sun-loving and will therefore grow well in the southern part of the plot. In the penumbra and even more so in the shade, the plant has no chance of flowering, and the color of the leaves and buds will become much duller.

When do I plant ornamental onions?

Autumn is the best time to plant ornamental onions. Thanks to their resistance to frost in winter, they will not be killed by frost, and in spring and summer, they will help to chase away soil insects, rodents, garden ants, butterflies, and bugs that do not like the smell of onions from the beds.