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Does Allium Spread on its own? [Clear The Inference]

If you ever hear Allium being invasive, do not blame onion or garlic, as other taller and larger wild species are the ones that might spread.

Generally, the Allium is a group of pungent flowering species where not all are well-behaving. The Allium wild varieties like Allium ursinumAllium triquetrum, Allium vineale, and Allium sphaerocephalon spread by self-seeding to give numerous stocks.

The list of spreading ones does not end here, as Allium holds more than 500 species. So continue to know about the invasive ones with their growth habit.

How Fast Does Allium Spread?

The umbels with numerous star-shaped flowers of Allium are glorious to the eye but dangerous to the ground.

Mainly the ornamental Alliums with bigger umbels pose a threat of spreading since they start seed formation as soon as flowering ends.

However, Alliums grow slowly from seeds and are not true to the type. It is because the seed takes about 12 weeks to 1 year to give out the first bulb.
The purple bloom of Allium with its seed
Each flower in the umbel of Allium produces its seed.

Also, since the foliage part is a biennial, the flowering starts in the second year of the plantation, from late spring to early summer.

So as per the lifecycle of Allium, it might take them about three years to specifically multiply their number. Summer Beauty Allium is one of them to spread in the given time.

Are Allium Bulbs Invasive?

Allium growing from seeds does not justify their mother plant since they are hybrid and cannot stay true to themselves.

Meanwhile, some species like Globemaster and Allium millenium has sterile seeds. So multiplication from seed is not possible.

Such conditions demand bulbs to come into action, which is the most viable part of Allium to give new stocks.

These bulbs can multiply their number from small bulbils around the mother stock. However, they cannot spread on their own, making them non-invasive.

Ornamental Alliums are on the list of medium growers whose seeds cannot give the original type. That is when you need to plant the bulbs during the fall.

A single plant comes out from a single bulb, so spreading is never an issue for Allium growing from a bulb.

Moreover, the bulbs are perennial, giving out new leaves yearly after overwintering the cold. So dividing is unnecessary each year. Do it in 3 to 4 years.

You can expect the species to attain a height of 1 to 2 feet in their growing season. The growth height might make the Alliums appear as invasive.

How To Control Allium From Spreading?

Controlling the growth of Allium might not take much of your time as Alliums are rarely invasive.

However, you cannot let your guard down, as certain factors can trigger the spread. So follow the steps to prevent Alliums from spreading.

  • Deadheading: Snip off the blooms as soon as they complete flowering and before seed formation. It helps to cease the self-seeding of the plant.
  • Crop Rotation: Plant Alliums in another bed so that different crop grows in their previous bed. This might help to control the Alium spread to a certain extent.
  • Mowing: Cutting off Allium’s shoot part helps promote foliage growth instead of flowering.
  • Digging: Start over the growing process by digging a circle around bulbs to remove small bulbils from the ground.
  • Apply Mulch: Covering the root zone soil with mulches like newspaper and straw can prevent seeds from falling on the ground.
  • Use of Herbicide: Herbicide might not be effective in damaging the long leaves of Allium. But it can be applied after mowing to increase its effectiveness. It includes chemicals containing Glysophate or Dicamba.

From Editorial Team

Extra Tips!

Ornamental Allium with perennial bulbs die back to the ground as soon as the winter enters. This might make you think it has died, but they have gone dormant.

So if you plan to grow them for the next year, leave the bulb in the ground. And if not, dig them out to prepare dishes out of it.

The Choice Is Yours!