Purple Sensation allium

Sun

Full sun; tolerates light shade, but flowering and stem strength are usually better in sun.

Water

Water during active growth if spring is dry. Once the leaves die back, keep watering to a minimum; dormant bulbs dislike persistently wet soil.

Soil

Well-drained soil, including sandy or gritty loam. Improve drainage in heavy clay or use a raised bed; avoid sites that remain wet in winter.

Height

2-3 ft (0.6-0.9 m)

Spread

0.5-1 ft (0.15-0.3 m) per established clump

Flowers

Late spring to early summer; dense violet-purple globes about 3-4 in (8-10 cm) across.

Foliage

Basal, strap-shaped green leaves emerge in spring and usually yellow during flowering. Dormant through summer and winter.

Growth

Moderate; flowers from established bulbs each spring and gradually forms offsets.

Care needed

Low

• Pollinators
• Deer resistant
• Drought tolerant
• Cold hardy
• Low allergen

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

Difficulty

Easy

Toughness

Very tough

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

1. Planting day

   0.5 ft (0.15 m)

2. After 1 year

   2.5 ft (0.75 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 in autumn with the bulb base about 4-6 in (10-15 cm) deep, spacing bulbs 6-8 in (15-20 cm) apart.
• Water after planting and during prolonged dry spells while leaves are green; avoid keeping dormant bulbs wet.
• On poor soil, apply a light dressing of balanced fertiliser as leaves emerge; avoid heavy nitrogen feeding.
• Keep thick, moisture-holding mulch away from the planting area where drainage is marginal.
• Leave foliage until fully yellow, and lift congested clumps after it dies back if flowering declines.

Pruning. Cut off spent flower stems before seeds ripen if you want to limit self-seeding, or leave them standing for their dried shape. Remove leaves only once they have yellowed and withered.

Autumn

Plant bulbs in a sunny, well-drained position; use a raised bed if winter drainage is poor.

Early spring

Check emerging shoots for slug damage and feed lightly if the soil is poor.

Spring

Water during extended dry weather while leaves and flower stems are growing.

Late spring to early summer

Enjoy the flowers, then decide whether to retain seedheads or remove them before seed ripens.

Summer

Remove fully withered foliage and avoid routine watering over dormant bulbs.

Late summer to autumn

Lift and separate crowded clumps if necessary, then replant sound bulbs promptly.

• Plant repeated groups through a sunny border to create purple punctuation above emerging perennials.
• Grow among catmint, hardy geraniums or lady's mantle to conceal yellowing basal leaves.
• Combine with ornamental grasses in gravel or new-perennial planting for contrasting round and linear forms.
• Use in a cutting garden for fresh flowers and dried seedheads.

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

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

Wildlife: Flowers provide nectar and pollen for bees and other visiting insects. Deer and rabbits usually leave it alone, though no plant is completely browsing-proof.

• Bulb rot in wet soil: improve drainage, avoid soggy planting sites and discard soft or mouldy bulbs.
• Slugs and snails damaging emerging leaves: inspect young growth and use barriers, hand-picking or locally approved slug controls.
• Few flowers: move bulbs into more sun, allow leaves to die naturally and divide overcrowded clumps; very warm winters can also reduce performance.
• Unwanted seedlings: remove flowerheads before seed ripens and pull young seedlings while small.

All parts, including bulbs, leaves and flowers, contain Allium compounds toxic to cats, dogs and horses if eaten; poisoning can damage red blood cells and may be serious. Keep bulbs away from pets and seek veterinary advice after ingestion. For people, this ornamental allium should not be eaten; ingestion may cause nausea, vomiting or diarrhoea, especially in quantity.

• Star of Persia (Allium cristophii)

  Usually shorter, with much larger, more open flowerheads made of conspicuously star-shaped, metallic lilac flowers.

• Giant onion (Allium giganteum)

  Usually taller, reaching about 4-5 ft (1.2-1.5 m), with broader leaves and generally paler lilac-purple flower globes.

Allium is the Latin name for garlic, hollandicum means 'of Holland', and 'Purple Sensation' refers to the cultivar's conspicuous purple flowers.

Propagation. Separate offsets from mature bulbs after the leaves die back, then replant in autumn. It can self-seed, but seedlings take several years to flower and may not match 'Purple Sensation'; use offsets to preserve the cultivar.

Accepted botanical name

Allium hollandicum

Native range

Iran.

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