When to plant alliums?
The allium, also known as the ornamental onion, is one of the most beautiful spring flowers in the Dutch garden. The best time to plant an allium bulb is in autumn, but when and how? We explain it step by step in this blog. Because once you have seen such a purple bulb in full bloom, you will want to see it again every year!
When should you plant allium bulbs?
Allium bulbs often need to be planted fairly early, before temperatures really start to drop and the ground hardens. The ideal planting period is from September to November. During this period, the soil is still easy to work with, but cool enough to allow the bulb to root steadily.
Just like tulips and daffodils, allium bulbs need a cold rest period to bloom well in spring. So those weeks in the cold ground are not wasted time, because it all contributes to the blooming 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. So you can 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 bloom: a bulb that goes into winter well rooted will come up strong. One that has barely had the chance will often be left 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 varieties, that means 10 to 15 centimeters. Larger varieties, such as Allium Giganteum or Allium Globemaster, can be planted a little deeper, at around 15 to 20 centimeters. The tip of the bulb always faces up. Also ensure well-draining soil, because allium bulbs do not like to have wet feet!
Advice from Brenda: Unsure about your soil type? Mix some sand or compost into the planting hole; this greatly improves drainage. You can also always send me a message so I can help you think it through.
How do you plant allium bulbs step by step?
Planting alliums is easy. We notice that many of our inexperienced customers choose allium bulbs because not much can go wrong. As long as you do it properly, of course! Here is how you do 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 up
- Keep about 10 to 15 centimeters between the bulbs
- Cover the planted flower bulbs with soil and press down lightly
- Water once after planting and wait!
When does allium bloom?
That depends on the variety! Early-blooming alliums such as Allium Purple Sensation appear as early as April, while later varieties such as Allium Sphaerocephalon do not bloom until June or July. By combining different varieties, you can extend the wave of blooms in your garden from late spring well into the summer. That is one of the reasons we always recommend alliums as a complement to, for example, tulips and daffodils; they take over the bloom at the moment the spring bulbs finish flowering.
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 leaves to optimally reach pollinators. Bees and butterflies see that round bulb from afar. As soon as the alliums bloom, there is more insect activity than with any other spring flower. 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 garden activities to do together with children? The bulbs are large enough to hold well, digging the planting hole is a real digging job, and the result is simply wonderful! When those purple bulbs later stick out 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?
Alliums are real team players in the border. The round, floating flower heads provide height and structure in 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 finish blooming, the alliums come up. Ideal for a long period full of color.
- Alliums and daffodils: The yellow shades of daffodils form a beautiful contrast with the purple bulb heads of allium. Plant them together for a playful effect.
- Alliums and ornamental grasses: Ornamental grasses move in the wind and bring out the floating character of allium even better.
- Alliums and roses: Roses and alliums bloom partly at the same time, and the combination of rose flowers with neat bulb heads immediately gives your border atmosphere.
Order the most beautiful alliums from Bulbs4You
Would you like to add a few more beautiful and colorful alliums to your garden, balcony, or border? At Bulbs4You you will find a beautiful assortment of allium bulbs, freshly selected from growers in the Bulb Region. That way you get the quality your little garden deserves! If you order for €70 or more, shipping within the Netherlands is free. Do you have a question about alliums and planting them? Feel free to send me a message!
Frequently asked questions about planting allium
When does allium bloom?
Depending on the variety, allium blooms from April to July. By combining early and late varieties, you can enjoy those characteristic round flower heads for months.
Do allium bulbs come back every year?
Yes, alliums are perennial and most varieties simply come back on their own. They also slowly multiply on their own, so your border becomes fuller every year. So even more to enjoy every year!
What is the Dutch name for allium?
Allium is also called ornamental onion or bulb onion in Dutch. 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 make sure the bulbs are well covered in the ground. We recently wrote a blog about the toxicity of tulips, with 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 Centre (NVIC).
How far apart do you plant allium bulbs?
Keep about 10 to 15 centimeters between the bulbs. Larger varieties such as Globemaster may need a little more space, think around 20 centimeters. This way they can develop well and the bulb head will have the space it deserves.
Why do my alliums not bloom?
The most common cause is planting too late or having soil that is too wet. Allium bulbs that have not spent enough cold hours in the ground will bloom less or not at all. Also ensure well-draining soil, because stagnant water is the biggest enemy of the allium bulb.
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