One of the best qualities of alliums is their tough, prolific, hard-to-kill nature. One of the worst qualities is their tough, prolific, hard-to-kill nature.
It can definitely be a case of too much of a good thing. Left to their own devices, some alliums can spread prolifically.
You plant a cute little ornamental for a sunny corner and, suddenly, you’re finding them in places you never expected, or you’re battling what looks suspiciously like a wild garlic infestation in your lawn.
Whether you’re dealing with an ornamental that’s becoming a bit too over-exuberant or an unwanted wild species sneaking in, the sooner you get on top of the situation, the easier it will be.
To help you do that, here’s what we’re going to cover:
Are Alliums Invasive?
Whether you’re growing garlic, onions, chivesor one of the many gorgeous ornamentals, the vast majority of plants in the Garlic genus are not considered invasive anywhere in North America, and none of them are listed on any federal noxious weed list.
That said, some, such as wild garlic (A. grapes), three-cornered leek (A. triquetrum), and rosy garlic (A. roseum) can be restricted in some areas.
The common ornamental types aren’t as aggressive as the species mentioned above but some small-flowered types can be unruly, while the large-flowered ornamentals tend to be more polite.
The potential to become aggressive is influenced by your environment and local conditions, so the best way to determine if a specific species or even cultivar is troublesome in your neck of the woods is to check with your local extension office.
They can offer some guidance about what to watch for in your specific area.
A type that might become a nuisance in central California might be completely mild-mannered in Massachusetts.
Some ornamental cultivarslike ‘Globemaster,’ ‘Mount Everest,’ ‘Pinball Wizard,’ ‘Summer Beauty,’ ‘Tumbleweed,’ and most giant hybrids are sterile, so the seeds won’t germinate at all.
Some are semi-sterile, so germination will be limited. ‘Chivette,’ ‘Dallas,’ ‘Millenium,’ and ‘Pink Planet’ fall in this category.
How Alliums Spread
There are three ways that alliums spread themselves around. The first is through seeds.
After the pretty flower heads form, they turn to seed. The seeds blow on the breeze, are carried by birds, or drop to the ground nearby, where they germinate and take root.
Next thing you know, you’ve got a bunch of new volunteers.
Another way they spread is through the bulbs. Underground, the plant develops more and more bulbs as they mature, and these bulbs develop into new plants.
When alliums spread this way, they tend to become dense mats of foliage with few flowers.
Finally, they can expand via bulbils. A bulbil is essentially a tiny bulb-like growth that forms on the aerial parts of the plant.
As these mature, they become heavy and start to weigh down the stem until they reach the ground.
Then, they start a new plant where they touch down. The most obvious example of this type of reproduction is in Egyptian walking onions (A. x proliferate).
Controlling Spread
To keep alliums in check, you have to address all three methods of reproduction.
To stop both seeds and bulbils from spreading, deadhead your plants immediately after the flowers begin to fade. Just snip the stem off at the base.
I love the look of the big seed heads in the fall. They add such an interesting shape to the garden. If you agree, look for the sterile cultivars.
You can safely leave the seed heads in place without having to worry about them spreading. These types don’t produce bulbils, so you don’t have to worry about that, either.
To manage spreading bulbs, you need to get in there and either pull up the plants as they spread or divide every two or three years.
You’ll need to dig all the way down and remove the entire bulb, because any left in the soil will grow back.
You can share the bulbs with friends or start a new patch. Of course, if you’re growing an edible type, use them in your cooking.
If you’re dealing with a wild species that has crept into your lawn, mowing regularly will weaken the plants over time by cutting off their ability to photosynthesize.
It won’t eradicate them quickly, but it’s an easy way to keep them in check.
If you really want to limit growth, plant your alliums in a raised bedpots, or contained area. You’ll still need to deadheadbut you won’t have to worry about bulb spread.
Save the Onion Spread for the Dining Table
If you’ve got a problem with alliums spreading into areas where they aren’t welcome, taking some time to keep them under control means you can enjoy their prolific nature without the downsides.
What types of alliums are you growing? Are they getting unruly? Tell us about your experience in the comments section below.
And for more information about growing alliums in your gardenadd these guides to your reading list next:
