Can I Grow Allium in Pots? 11 Steps to "YES"
Allium is the epitome of cottage charm.
It looks like it came right out of a Dr. Seuss book.
BUT IT'S NOT MAKE-BELIEVE.
It's real and you can grow it!
Sure, you can plant allium in your garden.
But you want to grow it right out of a container.
Is that even possible? Of course.
I've done it and I'll show you how.
You can grow allium in a container for a big impact. Use a pot with drainage holes, add some high-quality potting soil, plant the bulbs at the depth recommended on the packaging, then add water, some cold weather, and some sunshine.
If you're serious, (I am) then let's start working on our Dr. Seuss-ish allium containers.
Don't drag your feet on this
Or the magic you will miss.
(See what I did there?)
I can also walk you through 13 easy steps to growing Dwarf Iris in containers HERE.
How to Grow Allium Bulbs in a Container
1. Plant Your Allium Bulbs in the Fall
First of all, be sure to plant your allium bulbs at the right time.
Allium bulbs should be planted in the fall when temperatures at night begin to reach between 45-50 degrees.
You can use this as a guideline to know when to plant your bulbs wherever you live.
I’m in zone 7 and always plant my bulbs in October whether I’m planting them in the ground or containers.
Allium in bloom is the epitome of "cottage" in early summer. Don't miss it!
Start thinking "summer" in the fall.
2. Choose a Container with Drainage Holes for Happy Bulbs
Allium bulbs will rot if they sit in water or soggy soil.
Did you hear me? This is tip numbers 1, 2, and 3.
Make sure the container you are using to plant your bulbs has drainage holes at the bottom of it.
If it doesn’t, you will need to drill out some holes if possible.
This assures any excess water won’t be trapped in the container.
Bulbs in standing water are certain failure.
3. Allium Bulbs Should be Planted between 4-8" Deep
When growing allium in pots, space them 4-8″ apart.
When you buy your allium bulbs, read the packaging to determine the proper depth you should plant them.
If you buy your bulbs individually, ask about the variety of the bulb so you can research it later to determine how deep it should be planted.
Allium bulbs should be planted anywhere from 4 to 8” deep, depending on the variety.
As a rule of thumb, bulbs should be planted about 2 times as deep as the size of the bulb.
Allium bulbs range greatly in size and recommended planting depth, so refer to the packaging for more exact depth.
I plant my allium at the depth recommended on the package even in containers.
This recommended depth helps to support them as they reach 2-4' heights.
They can be giants. And stunning. But can also flop so might need staking when they bloom.
Planting them at the depth recommended helps prevent some flopping.
Don't plant them too deeply, however, or they won't bloom. (Insert sad face.)
If this seems confusing, err on the side of 'not deep enough' and stake, rather than 'too deep' and no blooms.
4. Fill your Container with a High-Quality Potting Soil
The allium I was growing had a 5′ recommended planting depth. I filled my container with high-quality potting soil 6″ from the top of the container. The extra inch is to provide a basin to trap water and to prevent the soil from washing away.
This seems like a simple step (it is), but let me give a little tip to make it even easier.
I planted "Persian Blue" allium in my container this fall. The package recommends planting it 5" deep.
(Let's use this as an example but you can adjust these numbers according to the variety of your allium bulb.)
Measure down from the rim of your container to 5 inches then add 1 inch for a total of 6 inches.
Fill your container with high-quality potting soil to that 6-inch line.
The extra 1 inch is to account for the space to be left at the top of the container.
It will serve as a basin for water and prevent any potting soil from being washed away.
If in doubt, err on the side of planting your bulbs too shallow rather than too deep.
If the bulbs are planted too deep, they will not bloom and will decay over time.
5. Plant your Allium Bulbs Tips Up
Plant your allium bulbs with the tips up and the roots down.
Now it’s time to put your allium bulbs in the soil.
Place them with the tips up and the roots down.
When you are planting allium bulbs in a container, you can space them pretty close together.
You can put them so close that they are almost touching.
Keep in mind, however, allium can have huge flower heads.
If you are planting a larger variety of allium in a container, they may need more spacing to leave room for those amazing whimsical flower heads.
They can also compete with each other for nutrients so spacing may be the best bet with alliums.
I leave at least 2-3" between the smaller allium bulbs and 8" or more between the large allium.
If you don’t have enough allium bulbs to fill your container, don’t stress about it.
Take note of how many you are planting and next spring determine if you want to plant more (or less) the following fall.
6. Cover the Allium Bulbs with Soil.
Cover your allium bulbs with high-quality potting soil or mix, being sure the tips remain up.
Fill to 1 inch below the rim of the container.
As I mentioned before, that 1” space serves as a basin to capture water and also prevents the water from washing away the soil.
7. Sprinkle Some Bulb Fertilizer on Top and Water
Add bulb fertilizer to your winter container then water it in.
So much depends on the root development of the allium bulbs.
Throwing in some fertilizer isn’t necessary, but it might help.
I always do it because I feel like I’m giving my bulbs every chance I can to help them thrive.
After fertilizing, give your allium bulbs a good dose of water to get them off to a good start.
They won’t need a lot of water in the future (remember that bulbs will rot so they don’t need soggy soil).
However, you might want to give them a drink once every week or two if it doesn’t rain or if you are keeping them in your garage or shed.
Sometimes I go longer than that between watering and they still do well.
8. Keep your Bulbs in 32-50 Degree Weather for the Winter
Temperature is important with allium bulbs.
For the roots to develop at their best, most bulbs need about 6 weeks in temperatures between 32-50 degrees.
If the roots are well-developed, you can feel certain you will have a stunning display of blooms.
If the temperature drops below 32 degrees and your bulbs stay frozen for an extended amount of time, it may deter its ability to perform for you the next spring.
Or it may not sprout out at all.
To prevent your allium bulbs from freezing, you can keep your container in an unheated garage or shed throughout the winter.
If you are in Zone 7 like me, you can plant your bulbs in a container, leave them outside all winter, and enjoy the blooms in spring. (So easy!)
I planted my 'Persian Blue' allium bulbs in a concrete planter this fall and they should be fine.
Most of my containers have enough insulation to withstand our winters.
My only exception is my smaller clay pots.
I will bring them into my garage or shed when I know the temperatures are going to be below freezing for an extended amount of time.
Clay pots don’t offer as much insulation as my concrete planters do, so I tend to baby them a bit.
You can also choose to wrap some form of insulation around your pots if you are unable to move them.
Use bubble wrap or burlap or leaves or mulch or anything you have on hand.
9. Move your Container into the Sun When Temps Reach 50 Degrees.
When you start seeing 50-degree days, move any containers you stored in your garage or shed outside in the sun.
Make sure any containers that have been outside all winter are receiving full sun.
Fifty degrees means it’s time for the magic! Full sun will be your ticket to the best blooms.
The allium will burst forth spreading its show-stopping beauty in early summer.
This growing period is a good time to give them some water if you aren't getting rainwater to help them bloom their best.
Think about watering them every 3-5 days.
Enjoy these unique flowers in their prime time.
They are sure to deliver charm and fairytale interest.
They won't disappoint you.
10. After Allium Blooms Fade, Leave the Greenery in Full Sun.
After the allium blooms fade, you will be tempted to just cut the greenery down.
Resist the urge if you want beautiful blooms the following year.
The greenery is taking in nutrients from the sun and storing them down under the soil into the bulb.
Isn’t that crazy?
If you give your bulbs time to feed off our glorious sun, they will return next spring in all their beauty.
Feel free to cut off the spent bloom and stalk but leave the greenery.
You might want to move your container behind the shed or hide them away somewhere for this part.
Or leave the containers of allium with their spent blooms for their interest. I mean, they are so cool even when the flowers have dried.
Just be sure the containers are getting sun.
11. Store Allium Bulbs in Containers for Planting Again Next Fall.
You can leave your allium bulbs in your container untouched and expect another show the next spring.
You might want to add another dose of fertilizer to the soil after they bloom if you plan to leave them and give them a chance.
Or you can dig them up, cut off the now yellow or brown stems, and store the bulbs in a cool, dry place.
Make sure they have time to dry out.
Then put them in a brown paper bag and label them.
Next fall, plant them again in a container or the ground.
Allium bulbs are SO EASY!
Once you have grown them successfully, you will NEVER DO WITHOUT THEM!
They are unlike any other flower out there offering perhaps the biggest impact for the effort involved.
You can also plant pansies or violas on top of your allium bulbs. This will give you color all fall, winter, and spring until the allium bursts out of its cocoon in early summer.
For an easy guide to planting PANSIES, see my blog HERE.
If you'd rather plant VIOLAS, check out this blog HERE.
If all of the above steps to planting allium overwhelm you, just put some potting soil in a container with drainage holes, put all the bulbs in, cover them up with potting soil, put them outside in the sun, and wait for spring.
They will most likely bloom!
And wipe away the winter gloom!
(I'm Dr. Suess rhyming.
Or at least trying.)
Okay, I'll stick to flowers! Let's start experimenting with allium!
FAQS
Can you plant allium bulbs in a container?
It is easy to plant allium bulbs in a pot. Make sure your container has holes for drainage and that you use good-quality potting soil. Plant allium 4-8" deep depending on the variety. Water and keep cold until spring.
For more details, scroll to the top.
When should I plant my allium bulbs?
Allium bulbs should be planted in the fall when temperatures at night begin to reach between 45-50 degrees. You can use this as a guideline to know when to plant your bulbs wherever you live.
I’m in zone 7 and always plant my allium bulbs in October whether I’m planting them in the ground or containers.
How long do my allium bulbs need to be cold to bloom well?
For the roots to develop at their best, allium bulbs need about 6-10 weeks in temperatures between 32-50 degrees. Good root development translates to the best blooms.
When will my allium bulbs start growing?
When temperatures reach above 50 degrees, your bulbs will begin to grow. It is truly like magic every spring. If you have them in your garage or shed, be sure to bring them outside in the sun when you see 50 degree temps. The sun will draw them on out and give them the nourishment they need.
How deep should I plant my allium bulbs?
Allium bulbs should be planted between 4-8” deep. The size of different varieties of allium bulbs differs greatly. The larger bulbs should be planted deeper than the smaller bulbs. All allium bulbs should be planted 2 times as deep as their size.
Scroll to the top for more details.