Want to learn how to grow Allium? This Allium care guide will show you how. Growing Allium is a relatively straightforward process. Once you know a few key things you will be able to fill your garden with these attractive flowers. A long lasting plant, alliums will bring color and definition to a range of planting schemes from late spring until mid summer.
Part of the amaryllis family of plants, Alliums are related to common vegetables such as elephant garlic and onions. They also make great cut flowers and their seed pods can be sprayed for attractive Christmas decorations.
This Allium guide will take you through everything you need to know about Allium flower care.
Tall and elegant alliums are a stately addition to any garden. Allium can be used to add structure or definition to borders. The spent deadheads of the allium then give way to attractive seed heads, providing interest long after the blooms are spent.
Varieties of Allium
There are over 700 different Allium varieties commercially available. This means that there is plenty of choice for your garden.
- Drumstick Allium (Allium Sphaerocephalon) – You’ll get one-inch flower clusters that bloom in the early summer months. They start off a greenish color that will start to look like a red clover as the time progresses in the season. They look best if you allow them to waft their way through your space so they can peek through other flowers.
- Corkscrew Allium (Allium senescens ssp. Montanum var. glaucum): The twisting and turning blue-green leaves give this plant its name. You can find this one set in the perennial section of your garden center since it doesn’t grow from a bulb, but it grows from a rhizome. It produces two-inch lavender flower heads that form flattened balls in mid to late summer.
- Globemaster: These flower stalks are super-sized, and they can easily top out at three to four feet tall. They form flower balls that are 8 to 10-inches in diameter. Mount Everest is another tall, imposing allium that blooms in a creamy white.
- Japanese Onion (Allium thunbergii): This plant gets small pink flower heads that are an inch wide, and they bloom early in the fall months. They form a mop over a small globe. Some cultivars you want to look for include Ozawa with bigger purple flowers and Alba with white cup-shaped flowers. They grow from rhizomes instead of forming bulbs, and you can get them in containers.
- Nodding Onion (Allium cernuum): You’ll get flopping mop heads of flowers with this plant in pretty shades of purple and pink. The stems get between two and three feet tall, and it’s one of the most popular alliums because it can grow in partial shade.
- Purple Sensation: The flower stalks on these plants reach around two feet tall, and they can form two to four-inch bright purple flower globes. This can be a long-lived plant, and it has leaves that tend to get brown or yellow early, and this can distract from the flowers.
- Schubert Allium (Allium schubertii): The flower heads on this cultivar look like a miniature fireworks display. Even as they start to fade, they can keep their colorful look. The tumbleweed onion is another common name for this plant.
When selecting the allium or alliums for your garden, the choice on offer can feel overwhelming. Try to keep in mind how much space you have available. You should also consider your climate, soil conditions and what purpose you want the plant to serve. All these factors can help you to narrow your choice and select the perfect flower.
As well as being attractive, alliums are also popular with pollinators. They can provide a reliable supply of food late into the fall, when other sources are scarce.
The Allium Flower — Family, Genus, and Taxonomy
Allium is a genus of flowering plants that belongs to the Allieae tribe of the subfamily Alliodeae under the Amaryllidaceae family.
There’s a dispute over exactly which plants belong to the genus because it has a complicated taxonomy of evolutionary lines. As a result, species estimates range from about 260 to just under a thousand.
Botanical Characteristics, Colors, and Fragrances
These are herbaceous plants that will grow from bulbs, and they give you a distinct garlic or onion flavor or odor. They have green leaves on them that can be broad or coiled to straight. You’ll get several blossoms that will cascade down and globe-shaped in shades of pink, blue, purple, white, yellow, or red. They produce small, tight flower clusters.
Before we discuss Allium care, we first need to ensure that the bulbs are planted correctly. This may sound simple but many of the problems people encounter when growing Allium are because they are planted incorrectly.
Alliums are hardy to USDA zone 4. They will grow best and bloom in zone 4- zone 10 but gardeners outside of this zone range can also grow Allium flowers successfully.
As long as you can provide a few basic requirements, Allium care is relatively simple. Planting the bulbs in well drained soil in a sunny position will give them the best possible chance of thriving and reaching a full bloom.
Allium likes to grow in full sun positions. They also prefer well drained soil. If your soil seems heavy try working some grit or gravel into the soil before planting.
Alliums, and other spring flowering bulbs, are best planted in the fall or early winter. Flowering bulbs are generally less sensitive to extreme temperatures because the soil provides some insulation. In milder climates you can continue planting alliums until mid December or as long as the soil remains workable.
Spacing Allium Flowers
Like other aspects of allium flowers care, spacing depends on the variety of allium flowers you are growing. Larger Allium varieties, such as Globemaster, will require spacing to 11-14 inches. Smaller varieties will take up less room, requiring a spacing of between 3-6 inches. It is important to correctly space your allium bulbs. If the bulbs don’t have the room they require the Allium plant will become stunted and may struggle to flower.
Correct planting is a key part of Allium care. Properly spacing your bulbs, and planting them to the correct depth, ensures that they have room to grow. It also ensures that there is enough space for fresh air to circulate, significantly reducing the chances of the plants becoming diseased.
Similarly try to plant to the required depth. Planting deeply helps to improve the perennial habit of bulbs. Again smaller or medium sized varieties will thrive in a planting of 3-6 inches. Larger varieties will need more depth, 11-17 inches depending on the variety.
Planting Allium Bulbs
Alliums can be planted into the ground or into a container.
Plant Allium to the correct depth. If you are unsure try to plant to a depth of at least twice the bulb. If you are planting in containers ensure that there is space for a layer of soil about 1.5 inches thick between the bottom of the container and the bulbs. Cover with soil and firm down gently.
If you are planting into poor soil apply a potash feed in early spring. Potash feeds encourage the bulb and roots to form. It also helps to prolong the life of the bulb. Potash feed applications will benefit all spring flowering bulbs.
While feeding is not necessary for correct Allium care, applying a potash feed can help to encourage the bulb to flower. This is particularly vital in the bulbs first spring.
Allium Flower Care
Alliums may look like a majestically high maintenance plant, but Allium is in fact refreshingly easy to care for. Here is everything you need to know about Allium flower care.
Watering and Feeding
Watering is essential. The bulbs will require regular watering. If you want to save on your water usage why not try harvesting rainwater? You can then reuse this in your garden.
Regular watering is vital during dry spells and when the Allium plants are in flower. Alliums growing in containers will also require more frequent watering.
Regularly watering the plants is a key requirement for good Allium flower care. Plants growing in dry conditions, or in containers, will require more regular watering. After a period of heavy rainfall it is best to wait for the soil to dry before watering.
You won’t need to feed plants if you regularly amend your soil. Flowers in poorer soil will also benefit from a regular application of balanced fertiliser. This should be applied when the flowers begin to set. If you don’t want to buy chemical fertilizers, you can make your own liquid fertilizer. These can be just as effective as purchased fertilizers.
Finally mulching the beds in early spring with an organic matter will give the plants an extra boost. Mulch also helps the soil to retain moisture. This means that the bulbs are less likely to dry out.
Alliums will only flower once a year, typically in late spring to early summer. If you have cared for it properly, starting late spring to early summer you should see a long lasting bloom. Once spent the dried heads can also provide an attractive feature in your garden.
While some gardeners choose to deadhead spent alliums, others opt to leave the seed heads in place. Allium seed heads create an interesting shape, adding a new fascination to your garden beds. While deadheading helps the plant to conserve energy, leaving the seed heads in place is not detrimental to correct Allium care.
Alternatively you can cut the heads away once flowering is concluded. Don’t cut the plant back completely. The leafy foliage should be allowed to remain in place. This encourages the plant to store energy in the bulb meaning that it will come back strongly again the following year.
Any withered or damaged leaves should be removed as quickly as possible.
Occasionally Allium will require you to make bulb divisions. This can be either when offsets or rhizomes form. If you don’t divide plants they can become overcrowded. This can stunt growth and lead to a diminishing in the plants flowering habit.
Bulb forming Alliums are slow to form. They will appear on the original bulb. To divide these, once flowering has finished, lift the bulb and remove the offset. The bulb and the offsets can be replanted immediately. Bear in mind that offsets can be slow to grow. This means that it will be a few years before they begin to flower.
Allium by Ting Chen / CC BY-SA 2.0 Rhizome forming Alliums are more noticeable. When the club begins to look crowded, lift and divide. This can be done at any time of the year but is best done in the fall when the bulbs are dormant.
Harvesting Seed Heads
Once your flowers finish blooming in the summer months, you can leave the decorative seed heads into the garden. They offer a sculpture appeal but lose the purple color. You can harvest them for crafts and flower arrangements. If you want to use them for flower arrangements, you should try to keep the stems as long as you can. The seed heads will last without needing to put a sealer on them.
The stem gets woody and they’ll look beautiful for years if you keep them inside. If you leave them unprotected outside, they can break down over the season. However, you can easily paint them to add protection and color if you want to keep them outside.
The Drying Process
The type of flower or flowers you grow inside can help you decide which craft project you want to do. The drying process will take up to three weeks to complete. This can be a long time for your plants to hang undisturbed, so keep this in mind when you’re choosing your original spot for them to hang. The room should be dark, cool, and have good ventilation. You can run a piece of twine, clothesline, or wire in the room to hang them up by the stems in your space. The goal is to create a mini, secure drying line just like you use to dry clothes.
If you’re ready to dry them, get your flowers and remove any ancillary foliage. Group them in bundles of two or three stems before wrapping a rubber band around the midsection of the stems. Attach the bundles to the line using a paper clip or binder. Allow them to fully dry in two to three weeks, depending on the humidity and moisture levels in the home.
Put Your Dried Allium Heads to Creative Use
You could keep yourself busy for hours at a time with a fragrant home for months by using the dried flower heads to make potpourri. It’s a relatively simple process. You’ll have to mix dried allium heads with some lavender or rose oil before you stir them thoroughly while they’re in the oven for two hours.
If you’d like these flowers to keep their shape and form, you should put them in a shadow box or string them from a branch, dowel, or a decorative curtain rod with a garland. You can always give your dried flowers a home in a terrarium or wreath, but you may also want to spray them with a clear fixative to strengthen them and keep them easy to handle. If you have a steady and sure hand, you could press the flowers into an initial and display it under a picture frame or glass.
Common Pests and Problems
Allium is largely pest and problem free. As it is related to onions, and discharges a similar aroma, many larger pests and rodents tend to avoid them.
In wet conditions the plants may develop fungal diseases such as downy mildew. However as long as you have cared for it properly this is unlikely to occur. Leaf miners may also strike. But the damage is largely cosmetic so isn’t a major concern.
You will need to protect young and emerging plants from slugs and snails. Both chemical and organic solutions, such as coffee grounds, will work effectively.
Alliums as Companion Plants
Companion planting is a great way of encouraging plants to grow without using chemical methods. Alliums can thrive in a number of different schemes, from natural planting schemes to herbaceous borders. They will happily grow in your garden without inhibiting any other plants.
Untitled by Louise Leclerc / CC BY-NC-ND 2.0 Alliums are attractive and easy to care for addition to any garden that blooms in the summer. Capable of fitting into a range of planting schemes, Alliums provide both early and late season interest to your garden through the summer.
Is Allium Toxic?
There is a large dispute over whether or not ornamental allium is toxic to humans. It’s safest for you not to ingest allium because it can cause upset stomach or digestive issues. However, the plant is very poisonous for dogs and cats if they ingest it because it has organic sulfur compounds that will convert to highly reactive oxidants when it gets into your pet’s digestive tract.
Symptoms of allium toxicity in pets include elevated respiratory and heart rates, reduced appetite, loss of consciousness, weakness, lethargy, abdominal pain, diarrhea, and jaundice. Call your veterinary ER or veterinarian immediately.
Allium Flower Meaning and Symbolism by Color
In the flower language, alliums symbolize patience, good fortune, and grace. Since many blossoms sprout from one bulb, they represent unity too. In the Victorian Language of Flowers, the flower’s color also holds a significant meaning. Different allium varieties bloom in shades of burgundy, blue, purple, orange, pink, white, and yellow. Putting the following colors in a single bouquet offers symbolic meaning too:
- Blue – Blue flowers represent honesty, tranquility, and peace.
- Lavender – This color symbolizes grace, elegance, and youth.
- Orange – Orange is a vibrant color that represents excitement and passion.
- Pink – Pink flowers convey femininity, gentle love, affection, and happiness.
- Purple – The color purple can represent respect and royalty, and it’s classically royal. It also carries a strong sense of tradition and admiration.
- Red or Burgundy – Shades of red strongly represent romantic love. They can also represent courage and love.
- White – The color white will hold different meanings and depend on the occasion. At a baptism or wedding, they symbolize innocence and purity. At a funeral, they represent condolences and sympathy.
- Yellow – Yellow represents happiness, joy, and friendship. You can use this plant to spread cheer.
Allium Flower Meaning, Symbolism, and Cultural Significance
Apart from the pretty colors, these plants have a variety of meanings, like we outlined above. Unity is a big one since a lot of blossoms sprout from a single bulb, and they represent patience because they’re slow to bloom. They also represent good fortune, prosperity, and humility.
People have cultivated these plants for millennia. This is why they’ve become so culturally significant around the world for their use in worship, medicine, and cooking. They appear in the Quran and in the Bible, and William Shakespear referenced them in The Taming of the Shrew.
How to Care for Fresh-Cut Allium Flowers
For freshly-cut, long lasting allium blooms, you should trim the blossoms when they’re around ⅓ to ½ of the way open. Use clean, sharp garden scissors to cut the stems at an angle. Once you trim them, put the stems in a bucket of clean, cool water immediately after you remove them from the plant or hang them to dry. Before you arrange them in a vase, trim away any spent blooms and foliage that will end up in the water in the vase. Change your water every two or three days, or you may want to do so more frequently to prevent the grilled onion and garlic scent from filling your house.
Suitable Gifting Occasions for Allium Flowers
Since they represent prosperity and good fortune, these plants are the perfect thing to help wish a person good luck at the start of a new venture or life. They make wonderful graduation, birthday, or new career bouquets. During the in-season of May to June, they also represent unity, and this makes them a great wedding flower too.
Frequently Asked Questions
- Will alliums come back every year?
Yes, these plants are perennials. This means that they’ll come back every year without any help from you.
- Do alliums like shade or sun?
Nearly all allium cultivars like full sun with free-draining soil. Nectaroscordum is one cultivare that can tolerate slightly more shade, and some of the smaller allium cultivars can too, like Allium moly. You should plant early to mid autumn, so they do best when you plant them in September and October.
- Should you deadhead allium plants?
It’s only necessary for you to deadhead allium plants if you don’t want them to self-seed. To keep your garden free and neat of any seedlings, pink the yellowing or wilted bloom away from the stem directly below your flower’s head.
- Should you soak allium plants before you plant them?
You typically plant allium during the fall months. The roots will form in the fall and they will bloom in the late spring months the following year. Pick out a planting location that has well-drained soil, and it should get sun for at least half a day. Thoroughly soak your area with water once you plant the bulbs.
Decorative ornamental onions, alliums are more than just a pretty flower. A tough garden plant, Allium care is surprisingly easy. Meaning that with just a few basic steps you can enjoy their distinctive flowers from late spring through most of summer, typically till mid to late summer.
Jen is a master gardener, interior designer and home improvement expert. She has completed many home improvement, decor and remodeling projects with her family over the past 10 years on their 4,500 sf Victorian house. She is also a passionate farmer who keeps goats, chickens, turkeys cows and pigs on her farm, and an instructor for her community’s Organic and Sustainable Farming project.