If you want to look like you’ve taken your garden to the next level of design, ornamental alliums are the answer. Planting a few bulbs in the fall will create a mini-sculpture garden in the spring that will not only last while the flowers are fresh, but continue into summer as the flowers dry in place. The single globes float above the surrounding garden and are made up of tiny, individual flowers on thin, hollow stems.
They’re easy, very hardy, and with basal (ground level) foliage that is rapidly covered by other growing perennials, you won’t face the “what to do with yellowing leaves” issue that accompanies most other bulb plantings.
You can find ornamental allium in many different shades of purple, pink, red, blue and white, and in sizes that range from “wow!” to “ahh…how sweet!” Used to accent developing foliage of later bloomers, or provide the finishing architectural touch to a bed of spring favorites, allium will give your garden the professional touch you’re striving for.
Allium is a genus of flowering plants that includes hundreds of species, including the familiar onion plant While alliums like garlic and onions are commonly grown for culinary use, many gardeners also grow allium for their spectacular, unique blooms that add pops of color and whimsy to the garden.
If you want to add some allium to your garden for gorgeous flowers but don’t know where to start, this article will walk you through everything you need to know about growing allium plants outdoors.
Getting Started with Allium
Allium plants grow from bulbs that should be planted in the fall for blooms the following spring and summer The bulbs need a period of cold dormancy over the winter before they will bloom
When shopping for allium bulbs, look for plump, firm bulbs that show no signs of mold, damage, or rot. The bulbs should feel heavy for their size. Popular ornamental allium varieties include ‘Gladiator’, ‘Globemaster’, ‘Purple Sensation’ and ‘Drumstick’.
Where to Plant
Allium grow best in full sun (at least 6 hours of direct sunlight per day). They need well-draining soil and will rot if left in standing water or soggy soil. Amend clay soils with compost or other organic material to improve drainage before planting.
When to Plant
Plant allium bulbs in the fall, roughly 6-8 weeks before your average first frost. This gives the bulbs time to develop roots before the ground freezes.
Planting Depth
Plant the bulbs 4-8 inches deep, with the pointy end up. Deeper depths are better for larger bulbs. The width of the foliage can be used as a guide – plant the bulbs 3 times as deep as the bulb’s width.
Spacing
Space the bulbs 4-8 inches apart. Adjust spacing as needed based on variety – larger varieties need more space. Plant in clusters or groups for best visual impact.
Growing and Caring for Allium
With the right planting site and good fall planting, allium require minimal care and maintenance to thrive. Here are some tips for growing your allium blooms to their full potential:
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Water: Water thoroughly after planting in fall and periodically through winter if rainfall is lacking. Some occasional watering may be needed in spring/summer during extended dry periods. Avoid overwatering.
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Fertilizer: Work compost or other organic material into the soil before planting. No additional fertilizer is needed once planted.
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Pruning: Cut off faded blooms down to the stem to encourage more blooms. Allow the foliage to die back naturally – don’t cut it off. The foliage feeds the bulb for next year’s blooms.
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Overwintering: Leave allium bulbs in the ground over winter. Apply mulch after the ground freezes for cold protection.
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Division: Clumps can be divided and replanted every few years as the bulbs multiply. Division in spring or fall will result in more vigorous plants.
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Pests & Diseases: Alliums are relatively pest and disease free. Ensure good drainage to avoid bulb rot. Insecticidal soap can control aphids if they become a problem.
Allium Varieties to Grow
With hundreds of species in the allium genus, there are countless varieties you can add to your garden. Here are some top picks:
‘Gladiator’
A tall variety that bears huge 8-10 inch violet-purple globes on 3-4 foot stems. The blooms are eye-catching in borders or containers.
‘Purple Sensation’
A classic ornamental allium producing 4-5 inch spheres of vibrant violet-purple flowers on 2-3 foot stems in late spring.
‘Globemaster’
One of the largest allium varieties, ‘Globemaster’ has enormous 10-12 inch flower heads on 3-5 foot stems. The blooms open in early summer, later than most allium.
‘Drumstick’
A uniquely shaped allium with egg-shaped blooms on 1 foot stems. The flowers emerge deep maroon-red and fade to pink as they mature in early summer.
‘Millenium’
One of the few ornamental alliums that bloom in late summer rather than spring. The 2 inch bright pink flowers appear on 18 inch stems in August and September on this variety.
Designing With Allium
Allium add fabulous vertical interest to gardens and pair nicely with a wide variety of perennials and shrubs. Here are some tips for incorporating allium into your landscape design:
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Use taller varieties like ‘Gladiator’ as dramatic focal points in borders or beds.
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Plant shorter varieties like ‘Drumstick’ or ‘Millenium’ along walkways or the front of beds.
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Mix heights for dimension, planting taller allium near the back of beds and shorter varieties in front.
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Underplant with lower-growing perennials like salvia, catmint and coral bells that cover fading foliage.
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Plant in groups or clusters of at least 3-5 bulbs for maximum impact.
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Mix allium with other spring-blooming bulbs like tulips and daffodils.
With proper planting and care, allium will give your garden a beautiful boost of globular flowers year after year. Their vertical shapes and diverse heights allow for creativity in garden design. Add a few of these unique bulbs to your beds, borders or containers this fall and enjoy their vibrant blooms next spring!
When & Where to Plant Allium
Don’t make the mistake of digging a hole into hard, unforgiving soil, plopping in the bulb and then covering with rich, amended soil. Bulb roots go down – they need at least two inches of good soil beneath them.
Light: Allium thrive in full sun, but can tolerate part-shade conditions.
Soil: A well-drained soil is the most important condition for allium as bulbs may rot if left in wet soil. The average soil of most garden beds kept moist but not wet is generally fine.
Spacing: Space depending on the effect you wish to create – for single intensive plantings, space approximately 8-12” apart. For accents with larger varieties, space up to 2’ apart. While some species spread vigorously through seeds or bulbils, many varieties do not spread at all.
Planting: Plant bulbs in fall for a spring bloom. Plant dormant allium bulbs in the fall according to your growing zone. Plant them at a depth of 2-3 times their diameter (4-6”) in a well-drained sunny or partly-shaded site.
Allium is remarkably resilient in a dormant state and can wait to be planted, but needs to be in the ground a few weeks before the ground freezes in order to put down roots. If holding for any length of time, keep cool and dry in a dark location.
How to Grow Allium Throughout the Season
Growth Habit: Think: garden lollipop. In early spring, 2-3 flat, strappy leaves will emerge from the soil and remain close to the ground. By late spring, a single hollow flower stalk (scape) will emerge, with a papery tip. The spherical cluster of flowers will emerge when the scape is fully erect, though the foliage may already have started to yellow and die back.
Staking: Allium are remarkably strong for their height, but if you live in an area with high winds, it is wise to stake individual flowers.
Watering: Evenly-moist soil is preferred during the growing season. During the dormant season, bulbs can rot if too much moisture is in the soil.
Fertilizing: A small handful of bone meal placed in the soil at planting time is a good idea for root development. After a season in your garden, mulch with compost or well-rotted manure each year for added trace nutrients and improved soil.
Mulching: Allium doesn’t require mulching, but mulching for moisture retention, nutrients and aesthetics is perfectly okay.
Trimming & Pruning: You can remove the flower clusters either when fresh or dry, but it is crucial to leave the foliage intact, allowing it to yellow and die back naturally. Many gardeners leave the flower heads in place through the autumn as they have an almost architectural appearance.
Allium Planting Guide // How to Plant, Grow, and Care for Allium Flowers // Northlawn Flower Farm
FAQ
Where is the best place to plant alliums?
What do alliums grow well with?
Can alliums grow in soil?
They will grow in most any soil, as long as it is well-drained. Alliums adore sunlight and will perform best when they can bask in it all day long. Since most of them multiply naturally, they can be left untouched in the same area for years. Alliums are drought-tolerant plants that actually prefer to be grown on the dry side.
How do you grow alliums in a garden?
Start by incorporating 2-4 inches of organic matter, such as compost, manure, peat moss, or leaf mold, into your soil. This will help improve soil fertility, aeration, and drainage, ensuring your alliums have the nutrients and moisture they need to grow and bloom.
Should you plant Allium bulbs?
Planting alliums can be a rewarding experience for any gardener. These beautiful flowers, with their spherical heads and tall stalks, add a touch of elegance to any garden. However, to ensure successful growth and vibrant blooms, it’s crucial to follow the best practices and tips for planting allium bulbs.
Can ornamental alliums be grown inside containers?
Although not a common practice, ornamental alliums can be grown inside containers with moist soil, good circulation, and room temperature. A fan may be needed to keep the air moving. Ornamental alliums may resemble onions, but their flowers pop with these ornamental varieties. Learn how to grow them with these helpful tips.