Everything you need to know about allium bulbs
What is the best month to plant allium bulbs?
Allium bulbs need to be planted in early to mid Autumn. So, we would suggest planning to plant in October. As they are spring-flowering you can plant them at the same time as daffodils, tulips, and hyacinths.
Do allium bulbs multiply?
Once you have planted your allium bulbs you can expect them to germinate after 12 weeks. Under suitable conditions these bulbs will grow quickly and they will naturally multiply over 3+ years.
Do alliums come back every year?
Alliums are perennials so if they are planted in a well-suited environment they will not only bloom beautifully for the first year, they will return year after year.
How many allium bulbs should I plant together?
We recommend planting your allium bulbs relatively close together in rows of 10. You can find more information on planting allium bulbs in our blog post.
Do alliums like sun or shade?
It is best to plant your alliums where they will get as much sun as possible although most varieties will still tolerate some shade.
How late can you plant allium bulbs?
Alliums are best planted in October however you can plant them later if needed. Usually bulbs planted in October will give the longest flowering time so if they are planted later you can expect a shorter blooming time. The displays will still look good as long as the bulbs are planted before the first frost.
What happens when you plant bulbs too late?
Allium bulbs should be planted in autumn for the best possible results however you can plant them as late as December if the bulbs are still healthy. Do not plant bulbs if they are mouldy, soft or rotten as this could affect the other bulbs in the area. If you do plant allium bulbs too late they will not grow to their full potential.
Will dried out bulbs grow?
Yes, as long as the bulb is not mouldy. If the bulb is firm and plump it is likely to be successful when spring arrives. If the bulb is shrivelled and dry then it is best to throw it away.
Can you plant allium bulbs in pots?
Yes, but when planning to plant your alliums in pots you need to consider how deep they are. This is because alliums need to be planted at a depth 4x the diameter of the bulb. You will also need to make sure you have a well-draining container as you do not want to bulbs to soak and become rotten.
Why are my alliums drooping?
It is usually related the over or under watering of the allium bulbs. Although alliums can tolerate droughts they should still be watered during dry spells, especially if they are planted in pots as they can dry out quicker. If there has been no dry spells then it could be that the soil or compost is waterlogged.
Do you plant allium bulbs point up or down?
Alliums have a flat bottom and pointy top. The pointed side should be facing upwards when you plant them.
Does it help to soak bulbs before planting?
No, you should not soak bulbs before planting as it can cause them to rot. You just need to water them once planted.
Should you deadhead alliums?
Like most flowers it is best to leave the foliage to naturally die back before removing any heads yourself. However alliums can sometimes have foliage that turns brown when they are in flower, in this case there is no harm in removing the dead foliage.
How deep should I plant allium bulbs?
A well-known rule of thumb is the plant bulbs at a depth of four times the diameter of the bulb. Smaller allium bulbs can be planted 8-10cm apat whereas larger varieties should be 20cm apart.
What to do with alliums once they have finished sprouting?
Let the leaves die back naturally before cutting the remaining foliage to the ground. Once you have done this you can leave the bulbs in the ground ready for spring. You should plan to divide the bulbs every 3-4 years, replanting some in new areas and leaving others where they are.
Why did my alliums not come up this year?
There are many reason why alliums might not flower but the main causes are: The bulbs were planted too shallow
- You planted your bulbs at the wrong time of year
- A lack of sunlight (alliums need a lot of sun)
- The soil is too wet causing the bulbs to rot
How do you store allium bulbs?
The process of storing allium bulbs is like most other spring-flowering bulbs. You should first allow the bulbs to dry out before storing them in a paper bag or cardboard box. You can then leave them in a dark, cool room such as a garage or basement. Allow the bulbs to dry for a few days, then store them on paper in a cardboard box. Make sure you never store your bulbs in a freezer as this can cause the bulbs to dry out or become mouldy.
What grows well with alliums?
Alliums look great when paired with Iris flowers as well as peonies. As alliums are versatile plants they work well with any scheme but we think they look beautiful with white flowers for a delicate and romantic feel.
What blooms at the same time as alliums?
Iris and Nepeta bulbs will bloom at the same time as alliums.
How do I look after alliums?
As alliums are tolerant to droughts they do not need a lot of watering but must have access to a look of sunlight. Regular feeding is also unnecessary unless you have planted your bulbs in poor soil. If this is the case then you can apply a fertiliser.
Can I plant alliums in November?
It is best to plant allium bulbs in October to November but people in warmer climates can get away with planting their bulbs in December and even January.
Why are my alliums coming up blind?
Bulb blindness can be caused when you have removed the leaves prematurely the previous year. It is vital that you wait until the foliage has died back before removing the remaining leaves. However, if you did not remove the foliage too early it is possible that the bulbs were planted to shallow or you had bad frist during the winter months.
Are alliums poisonous to dogs and cats?
Yes, alliums are toxic to cats and dogs.
Why have my alliums died?
There is a very common problem known as allium white rot which causes alliums to die early. But it could also be that the blooming season has finished and the plant is naturally dying back.
Which alliums have the largest blooms?
The largest diameter in the allium family is the Star of Persia allium which can grow up to 12 inches in diameter. Allium Gladiator and Giganteum are tall as well as large in diameter.
Are Ornamental Onions and Allium the same thing?
Allium is the botanical name for garlic, onions, and chives, as well as the spring plants. Although they are the same family as onions they are not grown as food.
Where do alliums grow best?
Alliums prefer sunny spots in the garden with soil that drains well. It is best to plant taller varieties near the back of the border to help with stabilising them. Check out our guide on growing alliums in borders.
How many years do alliums last?
Alliums are perennials so will last many years but will need to be divided every 3-4 years.