Mount Everest ornamental onion

Sun

Full sun; flowering and stem strength are best in an open, sunny position.

Water

Water moderately during active spring growth if rainfall is scarce. Keep relatively dry during summer dormancy and avoid waterlogged soil in winter.

Soil

Well-drained soil, including sandy or chalky soil. Improve heavy clay drainage or use a raised bed; avoid wet hollows.

Height

3-4 ft (0.9-1.2 m)

Spread

1-1.5 ft (0.3-0.45 m), including the spring foliage

Flowers

Late spring to early summer; rounded white flower heads about 4-6 in (10-15 cm) across.

Foliage

Broad, strap-shaped, grey-green basal leaves emerge in spring and yellow around flowering time. The plant is dormant above ground later in summer.

Growth

Moderate; established bulbs flower annually and gradually form small clumps.

Care needed

Low

• Pollinators
• Deer resistant
• Drought tolerant
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Fairly tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   0.5 ft (0.15 m)

2. After 1 year

   3 ft (1.1 m)

   full size

About 1 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Toxic

Growth rate

Moderate

• Plant bulbs in autumn about 6-8 in (15-20 cm) deep and 8-12 in (20-30 cm) apart, with the pointed end upward.
• Water during prolonged dry spells while leaves are green; stop routine watering once the foliage dies back.
• Apply a light dressing of balanced fertiliser as growth starts if the soil is poor; avoid heavy nitrogen feeding.
• Keep thick, moisture-holding mulch away from the bulb planting area, especially in wet climates.
• Stake discreetly in exposed sites if stems lean; plants in sheltered, sunny positions usually support themselves.
• Lift and separate crowded bulbs after the leaves have died down if flowering declines.

Pruning. Leave the foliage until it is completely yellow and dry, then remove it at ground level. Cut spent flower stems down after flowering, or leave the dry heads for structure and remove them when they collapse.

Autumn

Plant bulbs in a sunny, freely draining position; use seasonal timing rather than northern-hemisphere planting months.

Winter

Check that the planting area drains freely and that containers are not standing in water.

Early spring

Apply a light feed on poor soil and check emerging leaves for slug damage.

Late spring

Water if conditions are unusually dry and support leaning stems in windy positions.

Early summer

Remove spent flower heads if you do not want dry seed heads; leave all green foliage intact.

Late summer

Remove fully dead foliage and lift crowded clumps for division while dormant.

• Repeat small groups through a sunny perennial border to carry white flower heads above lower planting.
• Combine with catmint, hardy geraniums or lady's mantle to conceal yellowing basal leaves.
• Use in a white garden with white roses and silver foliage for a restrained late-spring display.
• Plant among fine-textured ornamental grasses in a gravel garden, where the spherical heads provide contrast.

Garden styles it suits: White garden, Architectural minimal, English country, New perennial (prairie), Dry gravel garden and Formal.

Plant it with: Catmint, Hardy geranium, Lady's mantle, Salvia, Roses and Feather reed grass.

Wildlife: The flowers provide nectar and pollen for bees and other pollinating insects. Deer and rabbits usually avoid the onion-scented foliage, although no plant is completely browse-proof.

• Bulb rot in wet soil: improve drainage, move bulbs to a raised bed and discard soft or rotten bulbs.
• Slugs and snails damaging emerging leaves: inspect young growth and use barriers, hand removal or locally approved controls.
• Poor flowering from shade, crowding or premature leaf removal: provide full sun, divide congested bulbs and let foliage die naturally.
• Allium leaf miner where present: watch for lines of pale punctures and distorted leaves; remove affected material and follow local advice on pest timing and disposal.

All parts, including bulbs, leaves and flowers, are toxic to cats, dogs and horses if eaten; alliums can damage red blood cells and cause serious anaemia. This is an ornamental allium, not a culinary crop: do not eat it, and keep bulbs away from children and food supplies. Ingestion by people may cause stomach upset.

• Black garlic (Allium nigrum)

  Also has white flowers, but its heads are usually flatter or dome-shaped rather than rounded globes, and individual flowers have conspicuous dark green centres.

• Neapolitan garlic (Allium neapolitanum)

  Much shorter, usually about 1-1.5 ft (0.3-0.45 m), with loose clusters of white flowers rather than large, dense globes on tall stems.

Allium is the Latin word for garlic.

Propagation. Separate offset bulbs during summer dormancy and replant promptly or keep them dry and airy until autumn. Offsets retain the cultivar's characteristics; seed-grown plants may differ and take several years to flower.

Accepted botanical name

Allium stipitatum

Native range

Afghanistan, Iran, Iraq, Kazakhstan, Kirgizstan, Pakistan, Tadzhikistan, Turkey, Turkmenistan and Uzbekistan.

Sources: GBIF (CC BY 4.0) and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.