When you think of onions, you probably imagine the kind 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 new gardeners and experienced gardeners alike. They have stunning blossoms that add an architectural element to your garden even after the flowers have faded and gone to seed.
If you’ve ever grown chives, you can succeed with ornamental alliums. Ready to learn how?
The Best Species and Cultivars
Onions, shallots, and garlic are all members of the allium family. In total, over 200 allium species are suitable for growing in gardens, and there are more species out there that haven’t been discovered. Studies show there are at least 700 allium species out there!
How do you narrow things down? Ask yourself a few questions:
- What size of flowers do you want?
- Is there a particular color you are looking for?
- How much space do you have?
- When would you like the flowers to bloom?
- What plants will contrast nicely with the garden?
Once you have an idea, you can start the search. To make things a bit simpler, here are some excellent ornamental alliums you can plant in your garden:
Allium caeruleum has true, deep blue globes of star-shaped flowers on a 16-inch stem. Truly a stand-out option. Native to central Asia, it does perfectly well in USDA Hardiness Zones 2-10.
Drumstick alliums (A. sphaerocephalon) look like those mallets that drummers use, with purple-red heads with a green base on an 18-inch stem. Suitable for Zones 4-9.
At a stately four feet tall with big purple flowers, ‘Gladiator’ makes a real impact in the yard. It’s a Royal Horticultural Society Award of Garden Merit winner. Plus, it’s also drought-tolerant and naturalizes readily. This one is a cross between A. aflatunense and A. macleanii.
Grow in Zones 4-10.
Globemaster, a hybrid of A. cristophii and A. macleanii, has massive purple blossoms (up to eight inches in diameter!) on four-foot stalks. This one does well in Zones 4-10.
Dressed up in purple robes, this plant has massive five-inch flowers on four-foot stalks. It almost looks like a giant, showy chive plant. Perfect for Zones 4-8.
With reddish-purple blossoms atop three-foot stalks, ‘Mars’ is a reliable grower that stands out in Zones 4-9.
‘Mount Everest’ is an award-winning white allium with baseball-sized blossoms that stand on top of three-foot stalks. Absolutely stunning and ideal in Zones 4-9.
While most ornamental alliums have round flowers, A. moly features star-shaped yellow blossoms that brings sunshine to your garden. Sometimes called lily leek, it grows well in a range of climates from Zones 3-9.
A compact option at just two feet tall, ‘Pinball Wizard’ (a cross of A. macleanii and A. christophii) has giant purple heads with a hint of lilac and silver. It’s truly stunning and seems to change color in the varying sunlight. Does well in Zones 3-8.
Star of Persia
Allium cristophii, known as Star of Persia, is an exceptionally beautiful option. It has massive 10-inch heads with a reddish-purple color, but what stands out is the individual flowers on the inflorescence. Each one looks like a tiny star, giving the effect of a ball of stars on top of a 20-inch plant. Grow in Zones 5-8.
Tumbleweed onion (A. schubertii) looks like little fireworks exploding in your garden. The blossoms can be a food wide on a plant that is just 20-inches tall. It’s sure to draw 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 3-10, 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 that can be star-shaped, cup-shaped, semi-circular, round, or pendulous.
The best location for ornamental alliums is in a sunny spot where they can get plenty of light throughout the day. Even though most of these plants can grow in partial shade, giving them as much light as possible is best. Full sun with six hours or more is best.
Of course, the soil is another important factor when planting ornamental alliums. Ideally, ornamental alliums should have well-draining soil with a pH level of 5.5 to 6.5.
However, if the pH isn’t perfect, it’s not the end of the world. It’s more important that the soil is well-draining to prevent issues with root rot.
It’s also possible to grow these plants in containers.
As ornamental alliums are grown with bulbs, you need to carefully consider how you plant them in the ground. Autumn is a great time to plant your bulbs, so you can plan in the summer months to get prepared.
Dig a hole four times the diameter of the bulbs. If you want to grow several of these plants, you should space them apart appropriately.
For smaller alliums, a space of 3-4 inches should be fine. And, for taller plants, leave about 8-inches between bulbs.
If you’re interested in growing ornamental alliums in containers, you need to find a deep pot. Then, similar to growing in the ground, you need well-draining soil. A general-purpose potting mix will do the trick.
Looking After Ornamental Alliums
If you don’t enjoy constantly watering your plants, or you are busy traveling and won’t be around to give them a top-up of water, then you’ll be happy to hear that these plants are somewhat drought tolerant. They can handle a short period of drought.
That’s great 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 the top inch or two of soil dry out in between watering.
Keep in mind that there are rhizomatous alliums and alliums that have bulbous roots. Rhizomatous types can handle more water than bulb types.
Although fertilizer is not a must for growing these plants, if you have poor soil, then a balanced fertilizer will give your plant the extra nutrients it needs to keep thriving. Otherwise, if your soil is fairly healthy, you don’t need to feed your plants.
When they’re growing in all their glory, ornamental allium flowers are a sight to behold. But even as they fade and turn to seed, they can offer up some beautiful texture in the garden.
If you want, you can deadhead the plant after it blooms. Cut off the dying flowers if you want a tidy appearance or to prevent self-seeding. Not all allium plants are fertile, but many are, and they’ll spread unchecked if you aren’t diligent.
You can also decide to leave the seed heads on your plant if you like the look. Birds will appreciate the meal, as well.
Common Pests and Diseases
As we mentioned, this plant is closely related to onions, so it makes sense that they can fall victim to the same illnesses. We have a guide that covers all the most common ones.
Check on 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 cepivorum), which can linger 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 on the base of the bulb
Unfortunately, once this disease has established itself on the bulb, it’s nearly impossible to get rid of. However, there are a few treatments you can try. Head to our onion disease guide to learn more.
If you have to remove the plant, don’t plant anything in the allium family there for at least a few years. Or you can try solarizing the soil to kill off any pathogens.
Onion Downy Mildew
Again, this disease affects onions as well as ornamental alliums. This illness is caused by the fungus-like organism Peronospora destructor, which, 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 not overcrowding your plants and removing diseased areas.
There is no chemical solution for this disease.
Snails and Slugs
Two pests tend to eat away at ornamental alliums, and they are snails and allium leaf miners. You should be alert if you notice snail trails in your garden. If you do, head to our guide for some natural control options.
Allium Leaf Miners
Also known as Phytomyza gymnostoma these pests can be found on ornamental alliums. First, the adult flies lay larvae, and then the larvae slowly eat away at the plant. The flies are grey and roughly 3 mm long. The larvae are white, 8 mm long maggots.
The most effective solution for allium leaf miners is an insect-proof cover to block the flies from laying their larvae. Our article has more tips for addressing a leaf miner infestation.