If you are looking for a way to add unique pops of color to your landscape, then learning how to plant and grow allium is the perfect answer! They are like the “cake pops” of the garden world with their big, beautiful bloom spheres.
Allium bulbs are a part of the chive family and are considered ornamental onions. They are grown for their beauty as opposed to being edible. But unlike onions, their blooms do not put off a strong odor. Their stems and leaves can give off an onion-like odor if cut, which actually helps to make them deer and rodent resistant.
The leaves of an allium flower stay close to the ground while the plant shoots up a long hallow stalk that will have one single bloom on top. They look best when planted in groups for an eye-catching display.
Allium has a hardiness growing zone of 4-10. (Find your own USDA Plant Hardiness Growing Zone Here.) Their blooms typically appear later in the springtime after many of the other fall-planted bulbs begin to fade. They are a great way to extend your flower blooming season until those summer flowers are ready for show.
Because they come in a variety of colors and bloom sizes, they attract pollinators in large numbers. Bees and butterflies will definitely frequent your garden if allium flowers are included in the planting plan!
Varieties of Allium – How To Grow Allium
There are actually over 700 different varieties of allium bulbs to choose from. They come in a large variety of sizes that can range in size from 6 inches in height all the way up to 5 feet tall.
The size of each bloom varies as well. They come in bloom ranges of just a few inches across, to some that are more than 10 inches wide. Allium flower in hues of purple, red, pink, white, and even blue.
How To Plant, Grow, And Maintain Allium
Soil Requirements for Allium Bulbs
Allium bulbs prefer soil that is very fertile and, most importantly, well draining. The bulbs are very susceptible to rotting if they are planted in a low-lying area that constantly has wet and heavy soil.
Adding compost to your soil will help improve drainage in addition to adding vital nutrients. You can also add a bit of sand or tiny gravel to heavy soils such as clay. Both materials will help aid in drainage.
Allium bulbs also prefer a soil pH of around 5.5 to 6.5, and the soil temperature should be near 60º Fahrenheit (15º Celsius) or below when planted.
Planting Allium Bulb In The Fall
Allium is planted as a bulb in the fall. You can find allium bulbs in your local garden centers, nurseries, or even in many online stores. If purchasing online, make sure to immediately remove bulbs from their package once you receive them and store them in a dry, cool location until you are able to plant.
Make sure the location has plenty of air circulation and that temperatures stay between 40-70º Fahrenheit (4-21º Celsius). You need to plant allium bulbs a few weeks before your first hard freeze date. You can find that date by visiting Here.
Allium bulbs need time to get acclimated to the soil so they can set roots before they go dormant in the winter.
While some varieties will do well in partial shade, most prefer a location that receives full sun. Also, avoid windy locations if you plan to plant larger varieties. Because of their larger blooms and hollow stems, the large varieties may need staking as they grow.
Planting In Soil
Allium blooms typically look better when planted in clusters, but make sure to space bulbs 6 to 8 inches apart. This distance can vary depending on the variety. It is always best to follow instructions that come with each variety.
Start by digging a hole in your soil that is around twice the bulb’s diameter. For instance, if you have a bulb that is 3 inches in diameter, then your hole needs to be around 6 inches deep.
Add in a little bit of compost to the hole and then place the bulb in with the pointy end up. You may add a bit of bone meal if your soil is lacking in nutrients. Bone meal can also help to provide a bigger and more boisterous set of blooms.
Cover the bulb with a 50/50 mixture of soil and compost and lightly tamp down. Water thoroughly and then leave alone until spring.
If Planted In Containers
If you planted your allium bulbs in containers or pots, there is an extra step you should take during the winter. Containers and pots just can’t provide enough protection against the freezing temperatures in the Northern climates during the winter.
For these plants, bring them indoors and store them in a location that is below 60º Fahrenheit (15º Celsius). An unheated basement or garage works best. Once temperatures warm back up in early spring, you may place the plants back outside.
Long-Term Care – How To Grow And Maintain Allium
Allium bulbs planted in the soil should be left alone over winter since they will go dormant in the colder months. In the early spring, allium will emerge with bright green foliage. The foliage will continue to fill in as the temperatures warm.
Eventually, a hollow green stem will shoot up with a single bloom on top. This can happen anytime from mid to late spring all the way to early summer. And it can certainly vary from year to year depending on the weather.
You will rarely need to water your allium flowers. They can withstand extended dry periods and should only be watered in cases of drought-like conditions. Allium bulbs actually suffer more from over-watering as opposed to under-watering.
Since you added compost when planting, fertilizing isn’t really needed in the spring in order for allium bulbs to bloom. They should have plenty of nutrients from the compost.
You may wish to add mulch for aesthetic reasons or to help keep weeds at bay, but don’t add too much. Mulch can actually retain too much moisture and cause more issues for allium plants.
Pests & Issues
In addition to being deer and rodent resistant, allium is rarely bothered by pests or diseases. The main issue is to make sure the soil doesn’t stay constantly wet since this can cause downy mildew and root rot.
The blooms of allium flowers make great additions to indoor arrangements, fresh or dried. Cut the blooms when they are only a fourth of the way open to allow for longer storage. Just a note: Any faint onion-like smell quickly fades once the stems of allium flowers are in water.
Deadheading The Blooms
You may cut back the blooms of the allium plants after they start to fade, or you can leave them on the stems to dry out. Many gardeners like the look of the dried-out flowers.
Just make sure not to cut the foliage. Allow the foliage to stay so it can continue to absorb sunlight and create energy for the bulb to store for next year’s bloom cycle. You can remove the foliage in mid-summer or after it has completely died back.
Most species of allium are prolific seeders and thrive in the cooler growing zones. If you follow these tips on how to plant, grow, and maintain allium, you can continue to enjoy their beautiful pops of color in your landscape year after year!
Feel free to download, print out, or save our Allium At-A-Glance sheet. It is sized for half letter printing but can be scaled if needed.