Share
Alliums are a garden favourite amongst cultivars and other gardeners. With their striking appearance, they will undoubtedly make a worthy addition to any garden. However, knowing when to plant alliums is crucial for a vibrant display. In this article, you will find out the right time and seasons on when to plant alliums, so that you can see when do alliums flower, and what benefits that they will bring to your garden. Additionally, we’ll touch upon essential care tips and effective propagation methods to ensure your alliums thrive season after season.
Key Info:
- Name: Allium (Ornamental Onion)
- Scientific: Allium
- Category: Perennial Bulb
- Height: 1ft-6ft
- Care Level: Simple
- Sunlight: Direct
- Location: Edges, Pots
- Pot-friendly: Yes
- Attracts Pollinators: Yes
- Ideal for Bouquets: Yes
| x | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
| Plant | ✅ | ✅ | ||||||||||
| Flowers | ✅ | ✅ | ||||||||||
| Cut back | ✅ | ✅ |
Growing Alliums
Plant alliums in sunlit areas with soil that’s damp yet drains well. For a striking display, plant them in large numbers. Pair them with short plants to cover their leafy base after they bloom. Allow the leaves to wither on their own post-flowering. The dried flower heads also add beauty, especially during winter. Each year, enrich the soil with decomposed compost or manure. These plants are great next to memorial benches as they allow the space to be brightened up making it more peaceful to be.
Selecting Alliums
When picking alliums, consider the layout of your garden. Are you aiming for scattered placements or grouped pot plantings? Do you prefer a wild prairie look or a structured design? While many alliums are purple, they also come in blue, white, yellow, and pink. Think about the flower’s size and the plant’s height. Flowers can be as small as a few centimetres or as wide as 20cm (8in), and plant heights vary greatly.
For instance, tall alliums like ‘Purple Rain‘ and ‘Globemaster‘ stand out when planted alone or in clusters. Allium christophii, a shorter variety, is ideal for pots. For a prairie feel, Drumstick alliums such as Allium sphaerocephalon are perfect.
Where to Plant Alliums
As you learn about when to plant alliums and when they flower, you will notice that alliums thrive in sunny areas with good drainage. They adapt to various soil types. Place tall alliums at the back and shorter ones at the front of garden beds. While they can grow in pots, their leaves might look less appealing post-flowering.
Before blooming, alliums sprout leaves. It’s wise to position them in the middle of a garden bed so their withering leaves are hidden as flowers bloom. For a hidden leaf effect, mix alliums with decorative grasses and other perennials.
For a standout effect, plant alliums in large groups in garden beds or let them spread naturally in lawns near your teak garden furniture.
What to Do When Planting Alliums
Dig a hole for the allium bulb that’s about four times its size, aiming for at least 15cm deep. It’s safer to plant deeper than too shallow. Avoid placing multiple bulbs in one hole. For a natural look, space smaller alliums 7-10cm apart and taller ones about 20cm apart.
If the ground is already damp, you can skip watering. In spring, if your soil is less fertile, add a balanced fertiliser.
Best Time for Planting Allium Bulbs
As well as knowing about when do alliums flower, you need to know the best time on when to plant allium bulbs. In the UK, autumn months, especially September to November, are ideal for planting allium bulbs. If you miss this window, you can still plant until the end of December. Just ensure the bulbs are healthy and free from mould. Late-planted bulbs might bloom a bit later the first year but should normalise by the second year. Make sure to watch your alliums grow year upon year, either outside or from the comfort of your own home with our wooden garden chairs. Plus, if you are interested in teak furniture, we offer plenty of options on our garden benches website, and have recently shared information that may be useful about how to revamp conservatory furniture.
Where to buy alliums online
If you wish to buy alliums in the UK, but do not know where to go, then check out these retrospective gardening sites below. Each of these will sell you quality alliums that will guarantee that, once planted, your alliums will flower promptly.
Caring for Alliums
Tall varieties of alliums might need extra support if they’re in windy areas. After the blooms fade, let them stay on the plant for added winter charm. Some people even dry the seed heads for indoor decor. Keep track of where you plant allium bulbs to avoid damaging them later.
Watering Tips
Alliums are good at handling drought, so ground-planted ones usually don’t need extra water. Avoid watering them too much in summer to prevent bulb rot. If you have potted alliums, water them regularly but avoid waterlogged soil.
Nutrient Needs
Feeding alliums isn’t usually required. However, if your soil is poor, a balanced fertiliser like Growmore can be applied in spring, and will ensure that your alliums bloom and flower accordingly.
Deadheading
While you can remove wilted flower heads from late flowering alliums, it’s not mandatory. The dried blooms can add a unique touch to your garden.
Winter Care
Ground-planted alliums are winter-hardy and need no special attention. Potted alliums are more vulnerable to cold, so move them to a protected area and shield them from excessive winter rain.
Staking
If you plant alliums deep enough and in sunny, sheltered spots, even tall varieties usually won’t need stakes due to their sturdy stems.
Dividing Alliums
Over time, allium bulbs can multiply and crowd an area of your garden. When this occurs, it’s time to thin them out. After they’ve bloomed, lift and separate the bulbs. You can replant them in a different part of your garden or donate them to some of your friends if they are willing gardeners too.
Interested in more gardening and flower tips? Check out our guide on how to grow dahlias.
How to propagate alliums
After a few years after your alliums have flowered, allium bulbs can grow and multiply. In some circumstances, white bulbs will be pushed out of the soil. During either the late autumn or very early spring, you should carefully lift the bulbs out of the soil and gently peel off the offsets so that they are ready to be planted straight into the soil.
Growing alliums: pests and problem solving
As you learn about alliums, including when do alliums flower and start to shoot in the UK, you are bound to come across a variety of pests, problems, and diseases which could slow down your allium flowering routines.
White Rot
Allium white rot is a fungal disease, which inhibits the growth of onions and other alliums. To prevent recurrent infections, clear and burn the affected plant material and avoid planting alliums in the same position for at least five years.
Onion fly
Onion fly maggots can do the most damage which will prevent alliums flowering, eating the roots of plants in the onion family. If this is happening, the plant may fail altogether, or you might notice yellowing leaves.
Therefore, you should simply dig the bulbs up – if you see any maggots or larvae, dispose of the bulbs immediately.
Downy mildew
Uneven weather (particularly if it is cold and damp) can lead to downy mildew to appear on alliums. Downy mildew usually appears as yellow, brown or pale green patches on the leaf surface and/or mouldy growth on the underside of the leaf. This can lead to the leaves to wilt and die.
To prevent this from happening, avoid congested clumps of alliums by lifting and dividing every couple of years to air in good air circulation. Additionally, you shouldn’t overwater or allow soil or compost to become waterlogged as this will also affect the progress of the plant. Instead, pick off and dispose of the infected leaves.
Allium leaf miner
Both the fly and the maggots of the allium leaf miner cause damage to alliums – the female flies puncture and feed on the leaves, while the larvae feed on the stems and bulbs. Both the flies and the pupae are about 3mm long. The plant is likely to show distorted or twisted leaves.
If these diseases or other pests are causing problems for your garden, check out these 11 fly repellent plants that you should consider planting in your garden.
Tips on Buying Alliums to Flower
When it comes to buying alliums, you want to make sure that you get your value for money, and are guaranteed that they will flower. Each allium breed will have different types, so make sure that you get a variety that has the right height for you. As well as this, if you are buying a mature allium, you do not want one that has mould appearing on it, and still appear fresh even after a week of purchasing. Once you have considered these factors, you will be on your way towards having alliums that flower appropriately.
For more tips about gardening, such as if you want to make your garden more private quickly, consider adding these fast growing shrubs. And if you are running low on ideas for your garden, then here are our top 20 garden ideas.
FAQs
Absolutely, alliums are clump-forming perennials, and with proper care, their numbers will increase each year.
Yes, alliums have the ability to self-seed. However, the resulting plants may not be identical to the parent plant, and it may take a few years for seedlings to reach maturity and flower.
Yes, despite being part of the onion family, which is safe for human consumption, alliums can be toxic to domestic animals, particularly to cats and dogs.
Most alliums prefer full sun exposure to grow and flower vigorously. However, Nectaroscordum siculum (Allium bulgaricum) can tolerate some shade.
Our alliums attract bees and other pollinators during springtime. Local beekeepers have confirmed that the resulting honey does not possess an onion-like flavour.
When planted deeply enough in full sun, where they won’t stretch toward the light, and in a sheltered position to withstand wind, even the tallest allium varieties typically do not require staking due to their sturdy stems.
Sources
Crocus. (2023). Allium ‘Purple Rain’. [online] Available at: https://www.crocus.co.uk/plants/_/allium-purple-rain/classid.2000030725/ (Accessed 29/08/23)
Farmer Gracy. (2023). Allium ‘Globemaster’ Bulbs UK. [online] Available at: https://www.farmergracy.co.uk/products/allium-globemaster-bulbs-uk (Accessed 29/08/23)
Raven, S. (2023). Allium sphaerocephalon. [online] Available at: https://www.sarahraven.com/products/allium-sphaerocephalon (Accessed 29/08/23)
Crocus. (2023). Search results for ‘allium’. [online] Available at: https://www.crocus.co.uk/search/_/search.allium /(Accessed 29/08/23)
Thompson & Morgan. (2023). Allium Bulbs. [online] Available at: https://www.thompson-morgan.com/flowers-plants-shrubs/flower-bulbs/allium-bulbs (Accessed 29/08/23)
Gardening Direct. (2023). Complete Allium Collection. [online] Available at: https://www.gardeningdirect.co.uk/item-p-630126/complete-allium-collection (Accessed 29/08/23)
Waterside Garden Centre. (2023). Westland Growmore Fertiliser. [online] Available at: https://www.watersidegardencentre.co.uk/westland-growmore-fertiliser (Accessed 29/08/23)
