Broad-leaved onion

Allium nigrum | Also known as: Black garlic, Allium multibulbosum | Rating: 3 votes | Print / Pdf

Black garlic is hardy and great for beginners, but definitely has no rum in it.

Allium nigrum is a great allium for beginners as it is renowned for being very hardy. It grows in clumps, with sturdy stems so it won't be too affected by the wind but it will prefer a sheltered position in the garden. The flower heads grow at the top of these stems in a half-sphere shaped cluster of white star shaped flowers. It will grow to around 70cm in height. It likes a sunny spot but it will grow fine in partial shade. If you're planting this in clay soil then add a little grit to the soil as it will love a well-drained soil.

Rate it:
Known dangers?
  • no
Dangers: comments
  • Skin reaction possible if you handle bulbs.
Height [m]
  • 0.4 - 0.9
Spread [m]
  • 0.4
Dominant flower colour
  • White
Flower Fragrance
  • No, neutral please
Flowering seasons
  • Early summer
  • Mid summer
  • Late summer
Foliage in spring
  • Grey-green
Foliage in summer
  • Grey-green
Propagation methods
  • seed
  • offsets
Growth habit
  • Upright
  • Acidic
  • Neutral
  • Alkaline
Hardiness zone
  • Z5-8
Heat zone
  • H9-1
Winter temperatures [°C]
  • -29 - -7
Heat days
  • 0 - 150
  • well-drained
  • well-drained but frequently watered
Soil type
  • sandy
  • Clay
  • chalky
  • loams
Sun requirements
  • Full sun
  • Sheltered
Standard category
  • Flowers & bulbs
  • Bulbs
Grown for
  • Attractive Flowers
Creative category
  • For Beginners
  • Colours
Garden type
  • Cottage garden
Garden spaces
  • Flower beds
  • Cut flowers
  • Borders
Gardening expertise
  • beginner
Time to reach full size
  • 2 to 5 years
18 Related plants



Alliums are plants of the onion family. It's easy to forget that the humble onion is more than just a vegetable, it is also a very attractive plant. There are many varieties, but their common feature is their beautiful flowers. Pom-pom heads on tall stalks, they are perfect for adding height to flower beds. The flowers are also generally pretty long lasting so you'll get to appreciate them for longer than some other flowering plants. Alliums are often purple flowered but there are other colours too. There are different sized plants and flower heads, all of which will look striking in your garden.

Allium Lucy Ball

Onion 'Lucy Ball'

PLANTS Allium 'Lucy Ball' | -40°C - -7°C beginner Full sun

Allium ‘Lucy Ball’ is an eye-catching plant with a massive ball of very tightly packed flowers at the top of a tall erect stalk. The flowers are a gorgeous bright purple and will stand out in any floral display. If you have a dull spot in your garden, this a great plant to bring it to life with. Allium ‘Lucy Ball’ can be prone to rot, so make sure it gets plenty of sunlight and is grown in a well-drained area.

Allium caeruleum

Azure Allium

PLANTS Allium caeruleum | -34°C - 4°C beginner Full sun

Allium caeruleum is also known as Blue Flowered Allium. Known for its’ bright blue colouring, this allium will grow well in a sunny spot but it isn’t very good with frost, so it’s best planted in pots and moved indoors over winter. The stunning blue flowers contrast well with the bright green stalks. The leaves are glossy and grow around the base, these die back before the flowers bloom leaving you with a very striking neat and uniform display of flowers. Perfect for a formal garden design.

white-flowered keeled garlic

PLANTS Allium carinatum subsp. pulchellum f. album | -23°C - -1°C beginner Full sun

If you’re a fan of plants with attention-grabbing appearances, adding allium carinatum subsp. pulchellum f. album or white-flowered keeled garlic to your garden design is a recipe for success. Grown from a bulb, this plant produces clusters of white, short-stalked flowers that are held aloft on narrow, elongated stems. Suitable for most types of fertile soil as long as it offers good drainage, this plant should be grown in areas that receive lots of sunlight. White-flowered keeled garlic turns bland rock gardens and flower borders into a feast for the eyes and will delight the senses in a variety of garden designs, from sprawling flower beds to compact courtyard gardens.

Allium cepa


PLANTS Allium cepa | 4°C - 4°C intermediate Full sun

Allium cepa or common onion is the most widely grown member of the allium family. The bulb of this plant, the onion, is used in cooking the world over. It has clusters of white flowers and blue green leaves that will wilt and die off, at this point the bulb will have grown and developed a dry outer layer. This is harvested and allowed to dry, ready for storage or immediate use. Onions are commonly eaten both cooked and raw. They contain irritant chemicals that can affect your eyes when you're cutting them. Evidence of onions being eaten as a food date back to 500BC. The ancient Egyptians worshiped the onion and were even buried with them.

Star of persia

PLANTS Allium cristophii | -29°C - -7°C beginner Full sun

Allium cristophii or star of Persia is a very attractive allium. The impressive flowers are loose clusters that form a ball shape up to a foot in diameter. The flowers themselves have narrow petals and are star shaped, a pinkish purple colour with a metallic look to them. Each flower head can have up to a hundred flowers in it. They make great dried flowers. It doesn't like conditions that are too damp, and can suffer from bulb rot and fungal conditions. It can grow up to three feet in height and will only grow in full sun.

Allium flavum

Yellow-flowered allium

PLANTS Allium flavum | -34°C - 4°C beginner Full sun

Allium flavum or yellow flowered garlic is a pretty and delicate looking flowering plant but it does have a strong garlic scent, so bear that in mind if you're considering it for your garden! It has narrow tall leaves that are a blue-green colour, and clusters of small bell shaped yellow flowers that droop on long flower stems. It grows to around 40cm in height. It's easy to grow in any type of soil. If you're growing it in clay soil, all you need to do is to add a little grit to improve drainage. It likes full sun and doesn't need any pruning. It won't be bothered by pests and is generally free from disease, however onion rot or downy mildew can occasionally be a problem. This species has been given an RHS Award of Garden Merit.

Allium giganteum

Giant Allium

PLANTS Allium giganteum | -23°C - 4°C beginner Full sun

Allium giganteum is commonly known as Giant Allium; as the name suggests this allium has massive flower heads and grows very tall. The blooms grow in huge tightly clustered baubles of bright purple star shaped flowers. The stalks are tall and devoid of leaves. The leaves of the plant grow around the base of the plant. If you want a plant with the wow factor then this is a good one to choose for maximum impact. Both in size and in colour this allium is truly impressive. Grown in a sunny spot it should do well.

Allium Globemaster

Giant Allium 'Globemaster'

PLANTS Allium giganteum 'Globemaster' | -23°C - 4°C beginner Full sun

Allium giganteum 'Globemaster' is shorter than some of the other giant alliums, being around 80cm tall, but what it lacks in height it makes up for in the size of the flower heads which are huge, around 15-20cm in diameter. The blooms are made up of a cluster of bright violet star shaped flowers that grow in a sphere. It's a very attractive variety which has been granted the Royal Horticultural Society's Award of Garden Merit.

Allium karataviense

turkestan allium

PLANTS Allium karataviense | -29°C - -1°C beginner Full sun

Allium karataviense or Kara Tau garlic has been given an RHS Award of Garden Merit. It grows in clumps with long, thick and wide grey-green leaves with a tinge of purple. The flowers are star shaped, a pale pink and white colour and grow together in ball shaped clusters. It isn't a tall allium, growing to just half a metre in height. It prefers full sun and a sheltered position. You should find it easy to grow if you plant in a spot that has good drainage. This one will work well in a rock garden.

Allium moly

Golden garlic

PLANTS Allium moly | -40°C - -1°C beginner Full sun

Allium moly or yellow garlic Jeannie is a sweet little allium, fully deserving its Award of Garden Merit from the Royal Horticultural Society. It will grow quickly and produce lots of lovely yellow flowers. It grows to just 40cm and works very well in a container. The leaves are narrow and grey-green in colour. It likes a sunny spot in your garden and will grow well in any well-drained soil as long as it is reasonably fertile. You won't need to prune this plant at all. It will naturally grow in an attractive bushy shape.

Allium neapolitanum

White allium

PLANTS Allium neapolitanum | -18°C - -1°C beginner Full sun

Allium neapolitanum or white garlic is often grown for its ornamental good looks. It will grow to between a foot and a foot and a half in height, so it's not the tallest of alliums, but it is very pretty, producing large heads of pure white flowers with a green centre. It's a hardy plant that is easy to grow, great for beginners. This allium has a sweet scent, rather than the onion or garlic aroma of many other alliums, so it's a good one to bring indoors as a cut flower. Grow in full sun and it shouldn't give you many problems.

Allium oreophilum


PLANTS Allium oreophilum | -34°C - -1°C beginner Full sun

Allium oreophilum is a beautiful and easy to grow allium. It grows to just 15cm in height, but what it lacks in height it makes up for in the beauty of the flower heads which are a loose cluster of mid-pink star shaped flowers with a dark pink stripe running the down the centre of each petal. It likes light soil with good drainage and plenty of sun. It won't need any pruning. If you want more plants you can easily divide this one to plant some of it elsewhere in your garden. Being brightly coloured and quite low growing, this plant is very well suited to the front of your borders. Perhaps in front of some other taller alliums.

Allium porrum


PLANTS Allium porrum | -7°C - -1°C beginner Full sun

Allium porrum or Garden Leek is mostly grown as vegetable, rather than for ornamental purposes, however it does have clusters of quite attractive white flowers which grow in the second year, so they do add some interest to a boring vegetable patch. Leeks have a milder taste than onions and are great for cooking with. Dried leeks have been found in archeological sites of Ancient Egypt and are also represented in Egyptian wall carvings. The leek was also the favourite vegetable of Emperor Nemo who thought it improved his voice. The leek is also the national symbol of Wales.

Allium roseum

Rosy Garlic

PLANTS Allium roseum | -18°C - -7°C beginner Full sun

Allium roseum or rosy garlic is so called due to its pretty rose pink flowers. It's an old world species that is edible as well as beautiful. It does have a strong garlic aroma, so strong that it repels squirrels from your garden, so if you have a problem with squirrels, this plant could do the trick. It grows to a height of around a foot and a half. The flowers each have six petals and grow in loose umbrella shaped clusters. It has long and narrow grey-green leaves. It's a hardy plant and will grow well in most types of soil as long as it has good drainage.

Allium schoenoprasum


PLANTS Allium schoenoprasum | -29°C - 4°C beginner Full sun

Allium schoenoprasum or chives, the pretty plant with the edible leaves. It has long thin and curved leaves that you can snip off and add to your salads. They have a peppery onion flavour. Chives are very easy to grow and they will spread rapidly. If you want chives elsewhere in your garden you can simply dig up a part of the clump and plant it in the new position. It has balls of purple flowers that grow on sturdy stems. This is the smallest of the edible members of the onion family. Chives will repel many insects so it's good to plant it near other plants that are targeted by insect pests. It will attract bees though. Chives grow up to around 50cm in height.

Allium schubertii

Ornamental onion

PLANTS Allium schubertii | -34°C - 4°C beginner Full sun

Allium schubertii or ornamental allium has stunning flower heads that look rather like a firework in mid explosion. The flower head is made up of up to 200 lilac star-shaped flowers that grow in a sphere but on stems of differing lengths. It grows up to 60cm tall and is a reasonably hardy plant that's fairly easy to grow. It likes full sun and well-drained soil. It may need a little extra protection in the colder weather. The seed heads are very attractive too so you won't need to dead-head this one or prune it.

Blue-flowered allium

PLANTS Allium sikkimense | -23°C - 4°C beginner Full sun

Allium sikkimense or sikkim onion is a delicate little plant from Asia with an enthereal feel, perfect for a cottage garden. It only grows to around 30cm high so is best suited to the front of your borders or for a container garden. It has light green leaves and pretty lilac or blue flowers that grow in umbrella shaped clusters of around 15 flowers each. The drooping flower heads are made up of lots of narrow petals giving them a feathery look. It will grow well in most conditions but will prefer a sunny spot.