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When you think of onions, you probably imagine the type you use in the kitchen. But did you know that they also have cousins that grow beautiful flowers? If you’re looking for something truly unique and eye-catching, growing ornamental alliums is for you.
These plants are ideal for both beginners and experienced gardeners. They have stunning blooms that add an architectural element to your garden even after the flowers have faded and gone to seed.
If you’ve grown chives before, you can have success with ornamental alliums. Ready to learn how?
Contents
The best species and cultivars
Onions, shallots and garlic are all part of the allium family. In total, more than 200 species of allium are suitable for growing in gardens, and there are more species that have not been discovered. Studies show that there are at least 700 species of allium!
How to reduce things? Ask yourself a few questions:
- What size flowers do you want?
- Looking for a specific color?
- How much space do you have?
- When do you want the flowers to bloom?
- Which plants will contrast nicely with the garden?
Once you have an idea, you can start researching. To simplify things a bit, here are some great ornamental alliums you can plant in your garden:
blue onion
Allium caeruleum has true dark blue globes of star-shaped flowers on a 16 inch stem. Truly a remarkable option. Native to Central Asia, it does perfectly well in USDA hardiness zones 2-10.
Pestle
Drumstick Alliums (A. sphaerocephalus) look like those mallets drummers use, with green-based purple-red heads on an 18-inch shaft. Suitable for zones 4-9.
Gladiator
Standing a majestic four feet tall with large purple blooms, ‘Gladiator’ makes a real impact in the yard. It is a winner of the Royal Horticultural Society’s Award of Garden Merit. Additionally, it is also drought tolerant and naturalizes easily. This is a cross between A. aflatunense and A. macleanii.
Grow in zones 4-10.
Globemaster
Globemaster, a hybrid of A. christophii and A. macleanii, has massive purple flowers (up to eight inches across!) on four-foot stems. This one does well in zones 4-10.
His excellence
Dressed in purple robes, this plant has massive five-inch flowers on four-foot stems. It almost looks like a giant, showy chive plant. Perfect for zones 4-8.
March
With purple-red flowers atop three-foot stems, ‘Mars’ is a reliable grower that stands out in zones 4-9.
Mount Everest
‘Mount Everest’ is an award-winning white allium with baseball-sized flowers that tower atop three-foot stems. Absolutely stunning and ideal in zones 4-9.
moly
While most ornamental alliums have round flowers, A.Moly features star-shaped yellow flowers that bring sunshine to your garden. Sometimes called a lily leek, it grows well in a range of climates from zones 3 to 9.
pinball magician
A compact option just two feet tall, “Pinball Wizard” (a cross of A. macleanii and A. christophii) has giant purple buds with a hint of lilac and silver. It is truly stunning and seems to change color in the varying sunlight. Does well in zones 3-8.
Star of Persia
Allium christophii, known as Star of Persia, is an exceptionally beautiful option. It has massive 10 inch buds with a reddish-purple color, but what stands out are the individual flowers on the inflorescence. Each looks like a small star, giving the effect of a ball of stars atop a 20 inch plant. Grow in zones 5-8.
Onion Tumbleweed
Onion Tumbleweed (A. schubertii) looks like a little firework exploding in your backyard. The flowers can be a large edible on a plant just 20 inches tall. It’s sure to grab attention wherever you plant it and is perfect for zones 4-10.
Planting ornamental alliums in your garden
Ornamental alliums can grow in USDA growing zones 3 through 10, with a few that will survive in zone 2 with some winter protection.
You can spot alliums by their long, strappy leaves and distinctive flowers. The petals tend to form clusters which can be star-shaped, cup-shaped, semi-circular, round or pendulous.
The best location for ornamental alliums is in a sunny location where they can receive plenty of light throughout the day. Although most of these plants can grow in partial shade, it’s best to give them as much light as possible. Full sun with six or more hours is best.
Of course, soil is another important factor when planting ornamental alliums. Ideally, ornamental alliums should have well-drained soil with a pH of 5.5 to 6.5.
However, if the pH isn’t perfect, it’s not the end of the world. It is more important that the soil is well drained to avoid root rot problems.
It is also possible to grow these plants in containers.
Plant bulbs
Since ornamental alliums are grown with bulbs, you need to think carefully about how you plant them in the ground. Fall is the perfect time to plant your bulbs, so you can plan for the summer months to prepare.
Dig a hole four times the diameter of the bulbs. If you want to grow more than one of these plants, you need to space them appropriately.
For smaller alliums, a space of 3 to 4 inches should suffice. And, for taller plants, leave about 8 inches between bulbs.
If you want to grow ornamental alliums in containers, you need to find a deep pot. Then, as with growing in the ground, you need well-drained soil. A general-purpose potting soil will do.
Caring for Ornamental Alliums
If you don’t like constantly watering your plants, or if you’re busy traveling and won’t be there to give them extra water, then you’ll be happy to know that these plants are somewhat tolerant of drought. They can withstand a short dry spell.
This is good news! You don’t have to be too diligent with the watering schedule. But your plants will be happier and healthier if you are. Try not to let more than an inch or two of soil dry out between waterings.
Keep in mind that there are rhizomatous alliums and alliums that have bulbous roots. Rhizomatous types can handle more water than bulbous types.
Fertilizer
Although fertilizer is not essential to grow these plants, if you have poor soil, a balanced fertilizer will give your plant the extra nutrients it needs to continue thriving. Otherwise, if your soil is healthy enough, you don’t need to feed your plants.
dead head
When growing in all their glory, ornamental allium flowers are a sight to behold. But even when they wilt and turn to seed, they can provide a nice texture in the garden.
If you wish, you can top the plant after it flowers. Cut off dying flowers if you want a neat appearance or to prevent self-seeding. Not all allium plants are fertile, but many are, and they will spread out of control if you are not diligent.
You can also decide to leave the seed heads on your plant if you like the look. Birds will also enjoy the meal.
Common pests and diseases
As we mentioned, this plant is closely related to onions, so it makes sense that they could fall victim to the same diseases. We have a guide that covers all of the most common.
Check your plants every few days so you can spot early symptoms of these diseases.
Onion white rot
A common disease that can affect ornamental alliums is onion white rot.
Onion white rot is a fungal disease that attacks the foliage and leads to root rot. This disease comes from the fungus Stromatinia cepivora (syn. Sclerotium cepivore), which can persist in the soil for years if left untreated.
Keep an eye out for these signs on your plants:
- Yellow foliage and wilting
- Root rot
- White, fluffy fungal growth at the base of the bulb
Unfortunately, once this disease has taken hold on the bulb, it is nearly impossible to get rid of. However, there are a few treatments you can try. Head over to our guide to onion diseases to learn more.
If you must remove the plant, don’t plant anything from the allium family on it for at least a few years. Or you can try solarizing the soil to kill any pathogens.
Onion blight
Again, this disease affects onions as well as ornamental alliums. This disease is caused by a fungus-like organism Peronospora Destroyerwhich, as the name suggests, can be destructive to your plant.
The most common signs of this disease are yellow leaves, white mold and shriveled bulbs. You can avoid this infection by avoiding overcrowding your plants and eliminating diseased areas.
There is no chemical solution for this disease.
Snails and slugs
Two pests tend to eat away at ornamental alliums, and these are snails and allium leaf miners. You should be vigilant if you notice snail trails in your garden. If you do, check out our guide for some natural control options.
Allium leaf miners
Also known as Phytomyza gymnostome these pests can be found on ornamental alliums. First, adult flies lay larvae, then the larvae slowly gnaw the plant. The flies are gray and about 3mm long. The larvae are white maggots 8 mm long.
The most effective solution for allium leaf miners is an insect cover to prevent the flies from laying their larvae. Our article has more tips for dealing with a leaf miner infestation.
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