How To Plant Alliums In Pots For A Stunning Late Spring Show!

Alliums are simple to grow and provide intense color when little else is flowering. They are the perfect flower for filling the lull in color that often occurs in late spring.

The tall, round flower heads also provide structure and height - making them perfect for use in borders as well as pots.

Planting in borders is very straightforward; just pop them in the ground (plant them twice as deep as the size of the bulb), and away you go. That is why, in this article, I will focus on how to plant Alliums in pots. So, with no further ado, let's get started!

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Planting Alliums In Containers

Planting Alliums In Containers

The first task will be selecting the correct pot. Alliums grow tall and need space, so you will need a big pot.

Allium bulbs come in a variety of sizes, but the common ones you will find in most stores will be around 4-6” in diameter. As a rough rule of thumb, the bigger the bulb, the bigger the flower and the more space they will need.

So, you will want a pot that is at least 12” deep and ideally 18” wide if you want to fit a few bulbs in.

Good drainage is also essential. Your bulbs will be in the soil all winter long, and if the drainage is poor, there is a good chance that they will rot.

Ensure there are lots of drainage holes in the pot and that these holes are off the ground so the water can escape. If you have a terracotta pot with a singular large hole, then put broken bits of terracotta over it to keep the soil in but allow the water to drain. You can also buy plant pot feet that lift the base of the pot off the ground.

A drainage hole in an allium pot — Raise drainage holes off the ground so pots can drain over winter, and during the growing season.

Pot pieces over a pot drain hole — Pieces of broken pots can help keep drain holes working properly.

This is the pot I have chosen. It is nice and big and has plenty of small drainage holes in the bottom that are already lifted off the ground - perfect!

An empty pot ready to plant with alliums — Fill the pot with soil to the desired planting depth.

Now we have our pot sorted, we need to fill it. I just use a good-quality potting mix for this. The bulbs will be going in 6” deep. If yours are a little larger, then plant them a little deeper - remember you want to plant them roughly twice as deep as the bulb is tall.

Because mine are going to be planted 6” deep, I fill my pot with compost until it is 6” below the top.

A partially filled pot for planting alliums — It's easy to place your bulbs in the pot if it is partially filled to the right planting depth.

Now, I can simply place all of my Alium bulbs on the soil surface and then cover them up.

If you are unsure of which way round to plant your bulbs, then look for last year's old root growth; this should be planted facing downwards.

An allium bulb with old roots showing planting direction — Put the root end down when planting bulbs (the shriveled bits are old roots--this side down).

Alliums need quite a lot of space, so you want to give them plenty of room. For my large pot, just five bulbs could be enough.

Five alliums in a container for growing — Large bulbs like alliums need plenty of space.

But I like to push my luck and love a display packed full of flowers. Because of this, I am going to sneak a few extra bulbs in!

Alliums bulbs in a planter — A crowded pot will be fuller (but may require more watering and feeding in the spring).

Once your bulbs are all arranged, you can fill the rest of the pot with your potting mix. Now, you could just leave it there, but your pot will be pretty boring over winter.

So, to spice it up a little bit, I like to add some winter flowering bedding plants to the top of the pot. These add a little bit of color over the winter months and really brighten the pot up.