Alliums can thrive in either full or partial shade, however full sun is preferred.
The bulbs are typically winter-hardy in hardiness zones 3–8. See this USDA Hardiness Zone Map to determine your growing zone.
Alliums require well-drained soil that does not become wet in order to be cultivated, just like the majority of other bulbs.
Where to Plant Alliums
Most alliums bloom in late spring, right after the last tulips and before irises and peonies, in perennial gardens. The flowers last for weeks and give the garden a balloon-like appearance as they float above it. After flowering, the foliage and flowers disappear, making space for summer perennials to take the lead. Allium christophii, Gladiator, Globemaster, Purple Sensation, and more excellent alliums for perennial gardens include these.
Alliums do well in rock gardens, where they flourish in the well-drained crevices between the boulders. Select species with smaller leaves, such as Allium sikkimense, Allium flavum, and Allium karataviense.
Alliums make great cut flowers, according to cutting gardens. The flowers remain a very long time and are easy to arrange thanks to their rigid stalks. You may guarantee that you’ll always have an abundant supply of flowers for bouquets by planting alliums in a cutting garden. You’ll receive flowers all season long if you select a variety. Purple Sensation, Allium atropurpureum, Mount Everest, Allium sphaerocephalon, and Allium tuberosum are all good choices.
Containers: Whether grown alone or in combination with other plants, many alliums thrive in containers. When the flowers blossom, you can relocate the planter to a visible location so that you can enjoy the flowers.
How to Plant Alliums
When to Plant: Bulbs-based alliums are planted in the fall, just after the first frost and before the ground freezes. Like other perennials, herbaceous alliums (such as Allium tuberosum and Allium millenium) have fibrous roots. You can plant these at any point of the growing season.
Planting Depth and Spacing: Planting depth is based on bulb size. Smaller bulbs, such drumstick alliums, should only be planted 3 deep in comparison to larger bulbs like Globemaster, which should be planted 5 to 6 deep. Follow the plant-specific directions on the packaging or on our website for the best results.
Planting advice: You don’t have to be concerned about deer, squirrels, or voles when growing alliums. Allium bulbs have an onion-like flavor that repulses them, and they almost invariably leave them alone.
What month should alliums be planted?
Most likely, when you think of alliums, you picture those plants with the traditional round, purple flowerheads on long stalks that make borders look amazing in late spring and early summer. Alliums, however, are much more than this.
There are alliums that are white, pink, blue, and yellow. There are some alliums that resemble a fireworks display, and others that resemble knotted dreadlocks.
You can identify that alliums are related to onions, garlic, and leeks by the aroma released when you crush the foliage. This family also includes chives (Allium schoenoprasum), which have delicious leaves that may be sliced and used to salads and dips.
Alliums are a favorite of butterflies and bees, and even the dried flowerheads look lovely in the border or in floral arrangements.
When to plant allium bulbs
The greatest time to plant alliums is in mid- to late-autumn, at the same time as tulips and daffodils that bloom in the spring. Allium bulbs are resilient and can withstand harsh winter weather if they are planted in soil that drains effectively.
Some attractive alliums, like “Allium sphaerocephalon,” flower in the late summer. Most ornamental alliums bloom in the late spring and early summer.
Where to plant alliums
The majority of alliums thrive in full sun and well-drained soil. Tall alliums should be planted in a protected area to prevent the stems from blowing over in high winds. Plant purple-flowered chives (‘Allium schoenoprasum’), which appreciate afternoon shade, or yellow-flowered ‘Allium moly’ in shaded areas.
Tall alliums look great planted in broad swaths or punctuated across a border. Late-summer bloomer Allium sphaerocephalon has gorgeous wine-red flowers that stand out amid the grasses in prairie planting schemes.
Long, slender leaves on ornamental alliums fade back as the flowers emerge. To conceal the waning foliage, place allium bulbs under other low-growing plants.
Planting allium bulbs
- Remove any weeds by turning the dirt over. Dig in leaf mold or compost instead of using manure on heavy soil as this can change the soil’s pH level. Alliums thrive in soil with a pH that is neutral.
- Make a hole that is roughly four times the bulb’s depth.
- Put a bulb in the opening with the roots pointing down.
- Gently compact the earth after filling the hole.
Alliums can also be grown in large pots with soil that is a mixture of grit, John Innes No. 3 compost, and multipurpose compost.
Tips on caring for alliums
- Ground-planted alliums typically don’t require irrigation.
- In the spring, alliums grown in containers will require regular watering. However, avoid letting the compost become soggy as this could lead to the bulbs rotting.
- Crushed eggshells around plants, copper tape around pots, beer traps, or wildlife-friendly slug pellets can all be used to deter slugs and snails from eating new spring leaves.
- When the plants are in bloom, spread a general-purpose fertilizer to aid in the development of the bulbs, assuring healthy flowers the following year.
- Once the leaves have withered back, remove them.
- There is no need to deadhead the flowerheads unless you choose to because they still look excellent after flowering has completed. As long as they remain in place at the border, they may be ignored.
- Put pots in a greenhouse or up against a wall of a house in the winter to shield them from the cold weather.
Growing allium bulbs from offsets
Offsets, which are little bulbs affixed to the main bulb, are produced by many allium bulbs. These can either be planted directly in the ground or split from the main bulb and placed in tiny pots to grow on. Before they have developed enough to produce flowers, it will take a number of years.
Wait until the allium plants are through flowering before using a garden fork to carefully uproot the plants and inspect the bulbs for offsets. Replant the bulbs after removing any offsets.
Best allium bulbs to plant
Alliums come in a wide variety, from large to little, with flowerheads that are rounded or exotic-looking twisted. Here is a selection of the most well-liked alliums.
- One of the most well-known alliums, Allium ‘Purple Sensation’ has the traditional deep purple spherical flowerheads on long, robust stalks. 1 m (3.5 ft) high.
- Large circular purple flowerheads up to 15 cm (6 in) across on robust stems that are 80 cm (3 ft) tall characterize Allium ‘Globemaster’.
- As its name suggests, Allium giganteum is a true giant with dense, spherical purple flowerheads on stems up to 1.8 meters (6 feet) tall.
How late can alliums be planted?
Yes! Alliums are annual plants that grow again year after year. Due of their extreme cold tolerance, they can endure most zones’ winters.
Alliums planted in the spring will still blossom, yes. Although the blossoms won’t be quite as big, they will return the next year in full force.
Allium may only grow as foliar growth, with no blooms, or not at all, if you plant it too deeply. To ensure the best growth and lessen the possibility of shallow bulbs being dug up by animals, try to put allium 4 inches beneath the soil surface.
The spring is not the time to transplant allium bulbs. Wait until the end of the summer when the foliage begins to turn yellow so that the plant will be in a dormant state and not be concentrating on new growth. It will be difficult to locate the bulbs if you wait until the stems totally wilt.
Select bulbs
- When dry bulbs are at their freshest, purchase them. When they are dormant, in the early spring, summer bulbs are on sale.
- Healthy bulbs will have a firm feel and be free of stains or damage. In order to have greater blooms, look for bigger bulbs.
When to plant
- Alliums, agapanthus, and cannas are examples of summer bulbs that should be planted in the spring when the earth is just starting to warm up.
- Because bulbs won’t start to grow in colder soil and may even decay, the ideal soil temperature is 13C. Try to plant dried bulbs as soon as you buy them.
- At the end of their dormant season, you should plant any bulbs you’ve preserved over the winter.
Soil type
- While different varieties of bulbs require different types of soil, summer bulbs generally prefer a warm, sunny location. Due to their susceptibility to rotting, bulbs require soil that may freely drain.
- Dig in one to two buckets of coarse sand per square meter if your soil is heavy with clay.
- Additionally, adding well-rotted organic waste will enhance drainage.
How to plant
- For many bulbs, dig a trench rather than separate holes for each one. Without pressing down too firmly, insert bulbs into the openings.
- Be certain that the developing point is pointing up. Firmly cover with soil.
- Bulbs that have been grown in a pot can be put right where you want them to bloom, such as in a border. This practice of planting “in the green” is known.
- For these plants, dig a hole that is both large and deep enough to accommodate the roots’ expansion before planting the bulb at the same depth.
- Many summer bulbs, especially delicate varieties, are perfect for patio pots. These can then be raised and kept during the winter.
Lifting and storing
- Since the majority of summer bulbs are not hardy, they must be removed before the first frost. In general, bulbs want to be kept dry.
- Eliminate any loose soil, carefully remove any dead or decaying leaves, and then leave the area to dry overnight. Fungicide dusting will aid in maintaining the health of the bulbs.
- In trays of nearly dry sand or dry paper bags, place the bulbs in a frost-free location.
- A few bulbs can be stored in slightly damp bark chippings because they prefer moist circumstances.
When should UK residents plant alliums?
Allium bulbs can still be planted for a fantastic spring show. The photographs demonstrate how Alliums, when planted properly, are low maintenance, return dependably each year, and are unquestionably one of the most fashionable plants for a border.
Alliums prefer a sunny location with well-drained soil, therefore they do not do well in wet, marshy soil, especially during the winter when the bulbs may rot. Alliums can be grown in containers for a patio display or placed in the borders if you don’t have the best growth conditions.
A. Moly, a bright yellow variety, and Chives, which the bees love (see second image), both of which grow to about 30 cm, are relatively little and perfect for the front of the border. The bees and we both enjoy eating chives, which make a great edging plant.
The outstanding Allium Cristophii (shown third image), one of the tallest kinds above 1m, and A. Globemaster are two of the taller types.
It is recommended to plant alliums in the first two weeks of October because they require to be planted in the early autumn. Bulbs may be purchased and planted for a lot less money than plants can this spring. As with all bulbs, it is ideal to plant them in pots that are four times as deep as the bulbs themselves.
Unusual variants include Nectaroscordum siculum, which is technically not an Allium but is sometimes sold as one (6th image).
Although most of us don’t have so much space, alliums look fantastic when planted in large groups, as in photographs 4 and 5, which are from an RHS garden. Alliums can be utilized well as a theme in smaller gardens when planted in groups and recurring perhaps 3/4 times. This will give a border true style.
Staking may be necessary for taller varieties, particularly in exposed places. Allium are simple to grow and put on a fantastic display. They offer good value for money because they come back and bloom year after year with little care.
Allium’s leaves are not appealing, especially after flowering, hence historically, companion plants like Achillea Mollis or Euphorbia have been planted with Allium to hide the leaves.
Alliums can I plant in January?
You might think that your days of planting bulbs are finished after the first frost or snowfall. But you can plant bulbs as long as the ground is usable! If you can dig a hole deep enough to plant, you can plant bulbs as late as January.
Do alliums reappear each year?
The foliage of the allium often appears at least a month before the flowers do. Some species’ foliage starts to turn yellow and die off before the flowers are fully open. Plant the bulbs with other plants that will obscure the wilting foliage to help mask it. Alliums do well with hosta, astilbe, and perennial geranium.
When your alliums are blooming, you may anticipate seeing a lot of pollinators. Any type of habitat garden will benefit greatly from the inclusion of these bulbs.
Like their relatives in the vegetable garden, alliums hardly ever have insect or disease problems. Rarely do bothersome rats and deer show any interest.
Most alliums are perennial plants. They will typically bloom again if the species you are planting is winter hardy and the bulbs are suitable to the growing environment in your yard.
Caring for Alliums After They Flower
Allium wasted flower heads can be removed or left in situ once flowering is over. The seed heads are viewed as an intriguing decorative element by many gardeners. Depending on your environment, they may persist far into the beginning of the fall.
Large-headed alliums like Schubertii and Globemaster hardly ever produce viable seeds. Purple Sensation and drumstick alliums will reseed if the conditions are favorable. Simply remove the seed heads after the flowers have faded and before the seeds develop to prevent a carpet of tiny volunteers.
There are herbaceous alliums as well as alliums that grow from bulbs, including varieties like Millennium and Summer Beauty. These plants have a big root system and come back every year to blossom.
Alliums that emerge from bulbs require their foliage in order to generate energy for the blossoms of the next year. Therefore, it’s crucial to let these plants die back organically. The leaves may typically be removed with a simple tug once it has turned yellow and dried. Trim off the wasted blooms from herbaceous alliums with hedge shears or scissors once they have stopped blooming. This will maintain the plants’ clean appearance and might promote a second flush of blossoms.