Are they aliens or flowers? One could say a little of both. Growing allium in your garden will seem like you have flowers from a different world. The purple ball-shaped blooms of Allium giganteum are the most recognizable allium. They are, however, not the only allium in town. Alliums are standout flowers that provide blooms late in spring. If you want some fun, quirky, and out-of-this-world flowers in your garden, add some allium bulbs.
For gardeners new to growing allium this guide will help answer all your questions. If you have grown allium before, this guide will help you learn more about the best ways to grow them and the different kinds that are out there.
Allium is a genus of ornamental flowering onions that have become increasingly popular in gardens over the last few decades. Their globular flower heads on tall, slender stems create a uniquely eye-catching display.
But when planting allium bulbs, a common question is: how many flowers will I get from each bulb?
The short answer is that generally you will get one main flower head per bulb. However there are a few factors that determine the number of blooms per allium bulb.
Flower Size Depends on Bulb Size
In most cases, one larger allium bulb will produce one larger flower. Giant varieties like Allium giganteum and Gladiator allium have tennis ball-sized bulbs and will develop enormous, 6-8 inch diameter blooms.
Smaller varieties like Drumstick allium have marble-sized bulbs and will produce cute, ping pong ball-sized flower heads
So if you purchase large, expensive allium bulbs, expect to get one very large, showy flower per bulb. With smaller bulbs, you’ll get more flowers per bulb, but they will be petite.
Planting Depth Affects Bloom Size
Proper planting depth is crucial for allium bulbs to reach their full potential. As a rule of thumb, bulbs should be planted 2-3 times as deep as the height of the bulb.
Planting too shallow limits nutrient and moisture uptake from the roots, resulting in smaller blooms. Overly deep planting can also inhibit growth.
Aim for the recommended depth and your allium flowers will reach their maximum size.
Bonus Blooms on Some Varieties
While one main head per bulb is the norm, a few allium varieties produce extra blooms:
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Drumstick allium can produce 1-3 spheres per stem.
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Azure allium often has double blooms.
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Flower heads of Purple Sensation alliums can multiply into large clusters.
So if abundant, multi-headed blooms are your priority, look for these specific varieties.
Age of the Bulbs Matters
Mature, multi-year bulbs tend to generate more flowers than young, newly planted bulbs.
As allium bulbs multiply underground over several years, each bulb accumulates more stored energy to fuel bigger, better blooms.
For the highest number of flowers per bulb, allow bulbs to remain undisturbed in the ground for at least 3 years before digging up and dividing.
Dividing Bulbs Boosts Bloom Production
Speaking of dividing, this process can encourage prolific flowering. As previously mentioned, mature clumps of underground bulbs will have higher bloom production.
By digging up and dividing overcrowded patches of allium every few years, you can propagate those high-performance bulbs around your garden.
Dividing also rejuvenates the plantings, preventing overcrowding that can limit nutrients and flowering.
Ideal Growing Conditions Maximize Blooms
Ensuring optimal growing conditions will enable your allium bulbs to realize their full genetic potential in terms of flower size and abundance.
Key conditions to provide include:
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Full sun
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Well-draining soil
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Even moisture during growth
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Lack of competition from weeds & other plants
Meeting these simple but important cultural requirements will allow your allium bulbs to thrive and produce their maximum number of spectacular blooms!
The Takeaway
To summarize, with proper planting and care you can expect each allium bulb to produce:
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1 main flower sphere per bulb
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Larger bulbs = larger blooms
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Some varieties generate bonus blooms
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Mature bulbs bloom more prolifically
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Divide bulbs regularly for vigorous flowering
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Optimal growing conditions are key
With this knowledge in hand, you can look forward to a bountiful floral display when your allium bulbs bloom. A planting of just 10-20 bulbs can create a spectacular spring focal point!
What To Plant With Allium
Allium bulbs that are planted in fall most often bloom in late spring. Plant bulbs and perennials that bloom in late spring to compliment and contrast the allium in your garden. Peonies, Bearded Iris, and Oriental Poppies are late-spring blooming bulbs that combine well with allium flowers. Perennials like Veronica, Salvia, and Butterfly Weed also bloom in late spring to early summer and they also look nice when planted with allium.
Bloom time is not the only characteristic to consider when planting your allium planting. Many varieties of allium have a strong geometric shape. In addition to the globe-shaped blooms, many varieties of allium are tall, growing over 4′ when mature. Tall varieties of allium such as Summer Drummer Allium, White Giant Allium, Allium giganteum, and Gladiator Allium are best planted in the back of a planting area.
Short allium varieties like Ivory Queen Allium and Drumstick Allium can be mixed into the front of a perennial bed. Planting the bulbs in groupings of 7-9 bulbs per planting hole will help create a full bouquet appearance.
Many allium varieties only grow 2-3′ tall. These mid-sized alliums like Star of Persia Allium and Purple Sensation Allium can easily fit into most planting beds.
Which Allium Have the Largest Blooms?
Big, bold, blooms are appealing for people growing allium bulbs. But, which allium varieties have the largest blooms? Although they aren’t the tallest of the allium, Star of Persia Allium has the largest diameter flowers. Star of Persia Allium blooms can grow up to 12″ in diameter.
Allium giganteum and Gladiator Allium are tall but also have large flowers. These varieties of allium blooms can grow up to 6″ in diameter.
How to plant allium bulbs for beginners
FAQ
Will allium bulbs multiply?
Do alliums like to be crowded?
How many allium bulbs should I plant?
How many flowers come out of one bulb?
Do Allium bulbs multiply?
Alliums are clump-forming perennials and will multiply on their own. Large bulbs begin multiplying 1-2 years after planting, while smaller bulbs multiply after 2-3 years. Alliums also form seed heads, which can be collected and replanted, although the seeds won’t be true to the parent plant. How deep should you plant allium bubs?
Do alliums grow well in pots?
Alliums also grow well in pots. Make sure to water your pot when dry, and not to overcrowd your bulbs. Plant allium bulbs into soil that is high in organic matter, and that has good drainage. It’s important not to plant in water logged soil, as this could cause your bulbs to rot. Plant allium bulbs with the pointy end up.
When do alliums flower?
Although alliums flower from late spring to early summer, the bulbs are planted in the fall. Allium bulbs need a period of cold to flower, and planting in the fall gives them a full winter to achieve this cold dormancy. After this period of dormancy ends, alliums will provide you with weeks of stunning flowers.
Do Allium bulbs need full sun?
Plant allium bulbs in an area that receives full sun to part sun. The sunnier the planting location the taller and larger blooms you will have. When growing allium bulbs they do have one requirement that is absolutely necessary for success. Like many other flower bulbs allium bulbs demand that the soil has adequate drainage.
Can you plant alliums in a perennial bed?
Short allium varieties like Ivory Queen Allium and Drumstick Allium can be mixed into the front of a perennial bed. Planting the bulbs in groupings of 7-9 bulbs per planting hole will help create a full bouquet appearance. Many allium varieties only grow 2-3′ tall.
Are alliums perennials?
Alliums are perennials, which means they return to the garden year after year. Alliums will even form new allium bulbs after several years. These bulbs can be dug up and planted elsewhere in the garden, where they will return the following year.