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Home > AUTUMN PLANTED BULBS > Alliums > Allium Giganteum
Allium Giganteum
Allium Giganteum Allium Giganteum Allium Giganteum Bulbs grown in a clump

Add dramatic height and bold colour to your garden with Allium Giganteum, one of the tallest and most impressive allium varieties available. Towering up to 1.5 metres (5 feet) tall, this majestic bulb produces spectacular globe-shaped flower heads made up of countless tiny, star-like bright purple florets. Each spherical bloom can reach up to 20cm (8 inches) in diameter, creating a truly show-stopping display in late spring.

Perfect for the back of borders, these striking blooms rise elegantly above other plants, adding vertical interest and architectural structure to any planting scheme. Whether planted in groups for a bold impact or interspersed among perennials for a more naturalistic effect, Allium Giganteum never fails to impress.

Plant the bulbs in autumn in well-drained soil and a sunny position — they require minimal care and will reward you year after year with towering blooms that not only look stunning, but are also loved by bees and pollinators.

These graceful giants are fast becoming a must-have among both experienced gardeners and enthusiastic newcomers, thanks to their reliability, resilience, and breathtaking display.

How to plant Alliums

  • Plant Alliums in the Autumn for Spring flowering.
  • Choose a location to plant your Allium Bulbs, they like to be in full sunlight and well-drained soil.

Planting Alliums in the Garden

  • Once you have found the perfect spot in your garden to grow your Alliums, you need to dig holes in the flower bed that are three times the diameter of the bulb. For example, if the bulb is 5cm (2") in size then it needs to be planted 15cm (6") deep.
  • Plant the bulbs about 20-30cm (8-12") apart. For impact, plant in groups.
  • Alliums work well in rockeries and crowded gardens as they don't take up much space.
  • Add horticultural grit to heavy soil to improve water drainage. 
  • The Allium bulbs need to be planted pointy end up.
  • Water the bulb well once in situ.
  • To help the soil drain well it is also beneficial to spread mulch, wood chips and organic matter over the entire planting area.
  • Alliums will flower around May/June.
  • Cut the Alliums back at the end of their blooming season. They will then continue to grow in your garden year on year with very little maintenance.

Planting Alliums in Pots 

  • Plant Alliums the same depth for pots as in the garden. Plant three times the diameter of the bulb. For example, if the bulb is 5cm (2") in size then it needs to be planted 15cm (6") deep.
  • For a garden with limited space, you may want to produce a fuller pot display of spring flowers by layering your bulbs like a lasagne. Simply plant your bulbs deeper to start with, with the largest or latest flowering bulbs further down, moving to the smallest and earliest flowering in the top layer. The shoots from the lower bulbs will find their way around the other bulbs. If you are planting the Alliums first, allow 10cm (4") of soil underneath the bulbs.
  • Use a good-quality, multipurpose compost. 
  • Add horticultural grit to heavy soil to improve water drainage. 
  • The Allium bulbs need to be planted pointy end up.
  • Water the bulb well once in situ.
  • To help the soil drain well it is also beneficial to spread mulch, wood chips and organic matter over the entire planting area.
  • Alliums will flower around May/June.
  • Cut the Alliums back at the end of their blooming season. They will then continue to grow in your garden year on year with very little maintenance.

Description

Add dramatic height and bold colour to your garden with Allium Giganteum, one of the tallest and most impressive allium varieties available. Towering up to 1.5 metres (5 feet) tall, this majestic bulb produces spectacular globe-shaped flower heads made up of countless tiny, star-like bright purple florets. Each spherical bloom can reach up to 20cm (8 inches) in diameter, creating a truly show-stopping display in late spring.

Perfect for the back of borders, these striking blooms rise elegantly above other plants, adding vertical interest and architectural structure to any planting scheme. Whether planted in groups for a bold impact or interspersed among perennials for a more naturalistic effect, Allium Giganteum never fails to impress.

Plant the bulbs in autumn in well-drained soil and a sunny position — they require minimal care and will reward you year after year with towering blooms that not only look stunning, but are also loved by bees and pollinators.

These graceful giants are fast becoming a must-have among both experienced gardeners and enthusiastic newcomers, thanks to their reliability, resilience, and breathtaking display.

Additional Information

Delivery / Returns

Spring Flowering Bulbs are delivered in the Autumn

Delivery and P&P

Spring Flowering Bulbs are dispatched from September to November.
All orders should be dispatched within 3-5 working days during this time. (Unless otherwise stated on the Shipping est.)
Postage cost to mainland UK (excluding N.Ireland, Highlands and Isles) is £4.99.
All out of area postcodes are charged at £9.50.
Orders over £60 qualify for FREE delivery to mainland UK (excluding N.Ireland, Jersey, Guernsey, Highlands and Isles).
Unfortunately, we are not currently delivering to the EU. See Delivery page.
When your order is due for dispatch, you will receive a tracking email from us to track your parcel.
Your parcel will be sent on a 48 hour tracked service with Yodel.

Returns and Refunds

You have the right to cancel your order at any time before it is dispatched.
All returns must be returned at your cost within 7 days of receipt.
Payment for the returned goods will be refunded within 7 days of the goods being received by us, less the postage charges. 



Planting & Growing Instructions

How to plant Alliums

  • Plant Alliums in the Autumn for Spring flowering.
  • Choose a location to plant your Allium Bulbs, they like to be in full sunlight and well-drained soil.

Planting Alliums in the Garden

  • Once you have found the perfect spot in your garden to grow your Alliums, you need to dig holes in the flower bed that are three times the diameter of the bulb. For example, if the bulb is 5cm (2") in size then it needs to be planted 15cm (6") deep.
  • Plant the bulbs about 20-30cm (8-12") apart. For impact, plant in groups.
  • Alliums work well in rockeries and crowded gardens as they don't take up much space.
  • Add horticultural grit to heavy soil to improve water drainage. 
  • The Allium bulbs need to be planted pointy end up.
  • Water the bulb well once in situ.
  • To help the soil drain well it is also beneficial to spread mulch, wood chips and organic matter over the entire planting area.
  • Alliums will flower around May/June.
  • Cut the Alliums back at the end of their blooming season. They will then continue to grow in your garden year on year with very little maintenance.

Planting Alliums in Pots 

  • Plant Alliums the same depth for pots as in the garden. Plant three times the diameter of the bulb. For example, if the bulb is 5cm (2") in size then it needs to be planted 15cm (6") deep.
  • For a garden with limited space, you may want to produce a fuller pot display of spring flowers by layering your bulbs like a lasagne. Simply plant your bulbs deeper to start with, with the largest or latest flowering bulbs further down, moving to the smallest and earliest flowering in the top layer. The shoots from the lower bulbs will find their way around the other bulbs. If you are planting the Alliums first, allow 10cm (4") of soil underneath the bulbs.
  • Use a good-quality, multipurpose compost. 
  • Add horticultural grit to heavy soil to improve water drainage. 
  • The Allium bulbs need to be planted pointy end up.
  • Water the bulb well once in situ.
  • To help the soil drain well it is also beneficial to spread mulch, wood chips and organic matter over the entire planting area.
  • Alliums will flower around May/June.
  • Cut the Alliums back at the end of their blooming season. They will then continue to grow in your garden year on year with very little maintenance.

Care Instructions

How to care for Alliums

  • Add a potash feed to enhance growth and strengthen the bulbs for flowering year after year.
  • Allow flower to die back and remove any dead foliage in early Summer.
  • Remove any dead stems that become detached from their bases.
  • Alliums are hardy and can therefore be left in the ground all year round.
  • Keep an eye out for any diseased foliage.
  • Seldom need support.
£6.00

Allium Giganteum

Ornamental Onions
  • 1 Bulb £6.00
  • 3 Bulbs £15.00
  • 6 Bulbs £25.00
Qty
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Flowering Period: May/June

  • Jan

  • Feb

  • Mar

  • Apr

  • May

  • Jun

  • Jul

  • Aug

  • Sep

  • Oct

  • Nov

  • Dec
Specification
Also known as: Ornamental Onions
Planting period: Autumn
Height: 120-150 cm / 48-59"
Border position: Middle/Back
Aspect: Full sun
Soil type: Loam, Sandy, Clay, Multipurpose Compost
Soil acidity: Any
Bulb size: 24cm+
Hardiness: Hardy - H5 (-10°C to -15°C)
Suitable for containers: Yes
Scented: No
Double flowered: No
Pollinator: Yes
Shipping est: Pre-order for delivery in Autumn 2026
Toxicity: Skin/eyes irritant
Delivery period: Autumn delivery (Oct to Dec 2026)
SKU harts11091
  • Description

    Add dramatic height and bold colour to your garden with Allium Giganteum, one of the tallest and most impressive allium varieties available. Towering up to 1.5 metres (5 feet) tall, this majestic bulb produces spectacular globe-shaped flower heads made up of countless tiny, star-like bright purple florets. Each spherical bloom can reach up to 20cm (8 inches) in diameter, creating a truly show-stopping display in late spring.

    Perfect for the back of borders, these striking blooms rise elegantly above other plants, adding vertical interest and architectural structure to any planting scheme. Whether planted in groups for a bold impact or interspersed among perennials for a more naturalistic effect, Allium Giganteum never fails to impress.

    Plant the bulbs in autumn in well-drained soil and a sunny position — they require minimal care and will reward you year after year with towering blooms that not only look stunning, but are also loved by bees and pollinators.

    These graceful giants are fast becoming a must-have among both experienced gardeners and enthusiastic newcomers, thanks to their reliability, resilience, and breathtaking display.

  • Additional Information
  • Reviews (1)
  • Delivery / Returns
  • Planting & Growing Instructions

    How to plant Alliums

    • Plant Alliums in the Autumn for Spring flowering.
    • Choose a location to plant your Allium Bulbs, they like to be in full sunlight and well-drained soil.

    Planting Alliums in the Garden

    • Once you have found the perfect spot in your garden to grow your Alliums, you need to dig holes in the flower bed that are three times the diameter of the bulb. For example, if the bulb is 5cm (2") in size then it needs to be planted 15cm (6") deep.
    • Plant the bulbs about 20-30cm (8-12") apart. For impact, plant in groups.
    • Alliums work well in rockeries and crowded gardens as they don't take up much space.
    • Add horticultural grit to heavy soil to improve water drainage. 
    • The Allium bulbs need to be planted pointy end up.
    • Water the bulb well once in situ.
    • To help the soil drain well it is also beneficial to spread mulch, wood chips and organic matter over the entire planting area.
    • Alliums will flower around May/June.
    • Cut the Alliums back at the end of their blooming season. They will then continue to grow in your garden year on year with very little maintenance.

    Planting Alliums in Pots 

    • Plant Alliums the same depth for pots as in the garden. Plant three times the diameter of the bulb. For example, if the bulb is 5cm (2") in size then it needs to be planted 15cm (6") deep.
    • For a garden with limited space, you may want to produce a fuller pot display of spring flowers by layering your bulbs like a lasagne. Simply plant your bulbs deeper to start with, with the largest or latest flowering bulbs further down, moving to the smallest and earliest flowering in the top layer. The shoots from the lower bulbs will find their way around the other bulbs. If you are planting the Alliums first, allow 10cm (4") of soil underneath the bulbs.
    • Use a good-quality, multipurpose compost. 
    • Add horticultural grit to heavy soil to improve water drainage. 
    • The Allium bulbs need to be planted pointy end up.
    • Water the bulb well once in situ.
    • To help the soil drain well it is also beneficial to spread mulch, wood chips and organic matter over the entire planting area.
    • Alliums will flower around May/June.
    • Cut the Alliums back at the end of their blooming season. They will then continue to grow in your garden year on year with very little maintenance.
  • Care Instructions
  • Ask the Experts
  • FAQs

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