When to plant alliums?
The allium, also known as the ornamental onion, is one of the most beautiful spring bloomers in the Dutch garden. The best time to plant allium bulbs is in the autumn, but when and how? We will explain this step-by-step in this blog. Because once you have such a purple globe in full bloom, you'll want it every year!
When should you plant allium bulbs?
Allium bulbs often need to go into the ground fairly quickly, before temperatures really start to drop and the soil hardens. The ideal planting time is from September through November. During that period, the soil is still easy to work with but cool enough to let the bulb root quietly.
Just like tulips and daffodils, allium bulbs need a cold dormant period to bloom well in the spring. Those weeks in the cold soil are therefore not wasted time, as it all contributes to the flowering period of this ornamental onion.
Until when can you still plant allium bulbs?
As long as the ground is not frozen, you can theoretically still plant allium bulbs. This means you could still do it well into December, although we do not recommend it. The later the bulb goes into the ground, the less time it has to root before winter. And you will notice that in the flowering: a bulb that enters the winter well-rooted comes up vigorously. One that has hardly had the chance often lags behind.
How deep do you plant allium bulbs?
The planting depth depends on the size of the bulb, but the rule of thumb is always the same: two to three times the height of the bulb. For most allium species, this comes down to 10 to 15 centimeters. Larger species, such as the Allium Giganteum or Allium Globemaster, can be planted a little deeper at about 15 to 20 centimeters. The tip of the bulb always goes upward. In addition, ensure well-draining soil, because allium bulbs do not like to have "wet feet"!
Advice from Brenda: Are you unsure about your soil type? Then mix some sand or compost through the planting hole; it helps drainage immensely. You can also always send me a message so I can think along with you.
How do you plant allium bulbs step-by-step?
Planting alliums is simple. We notice that many of our inexperienced customers go for allium bulbs because things usually can't go that wrong. Provided you do it right, of course! This is how you tackle it:
- Choose a sunny spot; alliums bloom best in full sun or partial shade
- Ensure well-draining soil and improve it with sand or compost if necessary
- Dig a planting hole two to three times the height of the bulb
- Then place the bulb with the tip facing upward
- Keep about 10 to 15 centimeters of space between the bulbs themselves
- Cover the planted bulbs with soil and press down lightly
- Water once after planting and just wait!
When does allium bloom?
That depends on the species! Early-blooming alliums such as Allium Purple Sensation appear as early as April, while later species such as Allium Sphaerocephalon do not bloom until June or July. By combining different species, you can extend the wave of flowers in your garden from late spring to deep into the summer. That is one of the reasons why we always recommend alliums as a supplement to, for example, tulips and daffodils; they take over the flowering at the moment the spring bulbs finish blooming.
Why does allium have such a long stem?
Fun fact! That is no coincidence. The allium has placed its flower head so high above the foliage to reach pollinators optimally. Bees and butterflies see that round globe from afar. As soon as the alliums bloom, there is more insect activity than with any other spring bloomer. That makes the allium not only beautiful but also valuable for your garden as an ecosystem.
Tip: plant ornamental alliums with your children!
Did you know that planting allium bulbs is one of the most fun gardening activities to do together with children? The bulbs are large enough to hold onto easily, digging the planting hole is a real digging job, and the result is simply great fun! When those purple globes later protrude above the border, the pride of a child who planted them themselves is truly priceless! And they learn a lot from it.
Combining allium in the garden?
Do it! Alliums are true team players in the border. The round, floating flower heads add height and structure to places where, for example, tulips have already finished blooming. These are our favorites to combine with the ornamental onion:
- Alliums and late tulips: While the last tulips are finishing, the alliums emerge. Ideal for a long period full of color.
- Alliums and daffodils: The yellow shades of daffodils form a nice contrast with the purple bulb heads of allium. Plant them among each other for a playful effect.
- Alliums and ornamental grasses: Ornamental grasses move in the wind and make the floating character of allium stand out even better.
- Alliums and roses: Roses and alliums bloom partly simultaneously, and the combination of rose flowers with sleek bulb heads gives your border an immediate atmosphere.
Order the most beautiful alliums at Bulbs4You
Would you like to add a few beautiful and colorful alliums to your garden, balcony, or border? At Bulbs4You, you will find a wonderful assortment of allium bulbs, freshly selected from growers in the Bollenstreek. This ensures you get the quality your garden deserves! If you order for €70 or more, shipping within the Netherlands is free. Do you have a question about the alliums and planting them? Feel free to send me a message!
Frequently asked questions about planting allium
When does the allium bloom?
Depending on the species, allium blooms from April to July. By combining early and late species, you will enjoy those characteristic round flower heads for months.
Do allium bulbs return every year?
Yes, alliums are perennial and return on their own for most species. They also slowly multiply by themselves, so your border becomes fuller every year. So, even more to enjoy each year!
What is the English name for allium?
In English, Allium is simply called Allium or ornamental onion. The name already reveals that the plant is related to the common kitchen onion.
Are allium bulbs toxic to cats and dogs?
Alliums belong to the onion family, which is toxic to both cats and dogs. Keep your pet away during planting and ensure the bulbs are well-covered in the ground. We recently wrote a blog about the toxicity of tulips, which includes tips that also apply to planting alliums.
In cats, even small amounts can lead to oxidative damage to red blood cells. If in doubt, you can find more information at the National Poisons Information Center (NVIC).
How far apart should you plant allium bulbs?
Keep about 10 to 15 centimeters of space between the bulbs. Larger species such as the Globemaster can have a bit more space; think of about 20 centimeters. This way, they can develop well and the bulb head will get the space it deserves.
Why don't my alliums bloom?
The most common cause is planting too late or soil that is too wet. Allium bulbs that have spent insufficient cold hours in the ground bloom less or not at all. Also, ensure well-draining soil, as stagnant water is the greatest enemy of the allium bulb.
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