Controlling Allium Plants – How To Manage Flowering Onions

Controlling Allium Plants – How To Manage Flowering Onions

Allium, known for its pungent aroma, includes more than 500 species, including the familiar onion, garlic, chives and a variety of beautiful flowering plants. Pollinators love the hardy, long-lasting plants, but deer and other critters usually leave them alone. If ornamental alliums are so practical and attractive, how could there be any problems with ornamental alliums in the garden? Read on to learn more.

Are Alliums Invasive?

Not all allium varieties are well-behaved. Some become weeds that are nearly impossible to get rid of, especially in mild climates. The bad news is that dormant bulbs can remain in the soil for up to six years.

The biggest offenders are wild allium (Allium ursinum), wild garlic (Allium vineale), and three-cornered leek (Allium triquetrum). All three spread like wildfire, quickly choking out gentler plants that you try to establish in your garden.

There’s really no easy answer when it comes to controlling allium plants. Be patient and persistent, as it will probably require several go-rounds. Oregon State University says to expect the process to take a minimum of three or four years, and maybe even more.

Controlling Allium Plants in the Garden

If you need more information on how to manage flowering onions, here are a few tips:

Pulling: Pulling may help, but only if you can manage to get all the bulbs. The problem with pulling is that tiny bulbs often break off when you pull the clump, and it’s very difficult to get them all, especially if your soil is hard and compacted.

Try pulling after a rainfall or water the area deeply a day or two ahead of time, but be aware that pulling may not be the final solution.

Digging: It isn’t much fun, but digging the old-fashioned way is probably your best bet when it comes to getting rid of invasive ornamental alliums in the garden. Dig a deep, wide area around the clump to get the tiny bulbs. Repeat the process every two weeks throughout the season.

Don’t shake the dirt off the clump; just place the entire plant into a box or bag so stray bulbs don’t escape. Discard the clumps, soil and all. By all means, don’t put the clump in your compost heap.

Mowing: Mowing doesn’t get rid of the underground bulbs, but cutting off the tops prevents blooms from developing seeds that generate even more plants.

Herbicides: Chemicals are generally ineffective because the substance doesn’t stick to the tall, slender, somewhat waxy leaves and does little to combat the underground bulbs.

However, if you want to give it a try, use a product containing 2-4 d, glysophate or dicamba before the plants reach 8 inches (20 cm.) tall. Mow immediately before treating the allium because newly mowed leaves have rough edges that improve absorption.

Controlling Allium in Lawns

If allium plants are popping up in your lawn, be sure to water and fertilize regularly. A healthy stand of grass is more likely to choke out the invaders.

Ornamental allium multiplying

Can anyone tell me which ornamental alliums do not multiply invasively? I have A. christophii and A. Mt. Everest which are very tame - a few offsets some years and slowly multiplying. I was told that A. Moly will multiply just like chives and would be everywhere - I just hate how much work that is to yank out - or dig one at a time.

Here are the ones I'm interested in from the Van Engelen catalog:

Allium azureum - blue, June

Allium cowanii - white, May blooming

Allium flavum - Small Yellow Onion June/July

Allium ostrowskianum, Syn: A. oreophilum - pink May/June

Allium pulchellum, Syn: A. carinatum, red-violet June/July

Allium triquetrum white May to July

Allium schubertii - purple May/June

Allium sphaerocephalon - purple Syn: The Drumstick Allium. "Great naturalizer with dense, crimson-purple, egg-shaped flowers". July - does naturalize mean a larger clump or takes over the world with seed?

I have a significant deer population and am working on adding alliums to my beds instead of lilies. Van Englelen has a good selection and their 2005 catalog will be posted in May - trying to plan ahead. I'm going to cross-post to the perennials forum. Thanks!

All about Herbs: Alliums (Chives, Garlic & Onions)

What are Alliums?

Alliums are hardy perennial herbs from the family Alliaceae . They are characterised by large rounded umbels of usually purple or white flowers at the top of leafless stalks. These flowers are followed by attractive seed heads that are a wonderful food source for birds and other wildlife. The majority of Alliums form bulbs but some, such as Welsh onions, Allium fitulosum, form thicken stalks. Alliums are both ornamental and edible making them a very useful herb to have in the garden.

There are many, many varieties of Alliums including the cultivated onions namely garlic, scallion, shallot, leek, and chives. The following have herbal qualities:

Welsh & Tree onions

Welsh onions, Allium fitulosum , and Tree Onions, Allium cepa Proliferum Group , make a good substitute for spring onions, as they are hardier and available earlier. They will grow in any well-drained fertile soil. Welsh onions may be picked at any time from early summer onwards. The bulbs of tree onions can also be pickled. The onion is believed to help ward of colds in winter and also to induce sleep and cure indigestion.


Garlic, Allium sativum , originates from India or Central Asia and is one of the oldest and most valued plant for both its culinary and medicinal properties. Historically the ancient Egyptians swore their oaths while invoking Onion and Garlic, which indicates that they considered these plants sacred.

Garlic is an indispensable culinary herb. In spring the flavour is lively, but from summer-time onwards, cloves should be split in half and the green filaments and sheath enclosing them discarded to make the garlic more digestible.

Traditionally garlic cloves are planted directly into the ground on the shortest day of the year and harvested on the longest. Garlic is also said to prevent leaf curl in trees, especially peaches. An interesting tradition, which is still held in rural New Mexico, is that garlic will help a young girl rid herself of an unwanted boyfriend.

Wild garlic

Wild garlic is also known as Wood Garlic, Ransomes, Ramsons, Devil ’ s posts, Onion flower, Stinkplant and Bear ’ s garlic. Different to other cultivated alliums, Wild garlic likes moist fertile soil, in either semi shade or full shade. Wild garlic self-seeds easily in wet and damp areas it can be invasive. In autumn, sow the seeds in a prepared site, cover lightly with soil. Germination will take place in early spring. Visit the Wild Garlic Jekkapedia page to watch a small clip on the history of Wild Garlic including how Florence Nightingale used it.


Chives, Allium schoenoprasum, are the only member of the onion group found wild in Europe. Their culinary virtues were first reported to the west by the explorer and traveller, Marco Polo. During the middle ages they were sometimes known as rush-leeks, from the Greek schoinos , meaning rush, and parson meaning leek.

The taste of chives is milder than onions, so they are the perfect choice for soups and savoury dishes. Chives should be added at the end of cooking otherwise the flavour will disappear. You should be able to cut chives down to 3cm off the ground 4 times a year to maintain a supply of succulent fresh leaves.

Traditionally it is said that chives planted next to apple trees prevent scab and when planted next to roses can prevent black spot. Hence the saying ‘ Chives next to roses creates posies ’ .

Where should you plant alliums?

Alliums are fairly tolerant regarding soil and position excluding wild garlic, see above, Jekka ’ s tips on where to plant cultivated Alliums are:

  • They prefer rich moist soil and, apart from wild garlic, prefer a fairly sunny position. If the soil is poor, they will turn brown at the tips.
  • Avoid planting in cold exposed or waterlogged conditions as bulbs can rot.
  • For best growth, plant 15cm from other plants.

Alliums make attractive edging. You can weave them through sunny borders or combine them with feathery grasses for best effect. Jekka visited a wonderful vegetable garden belonging to one of the top restaurants in our country and they had alternately planted garlic chives and chives to get different colours throughout the year. If planting as an edging you should plant at a distance of 10cm apart and allow to flower. For best results border alliums need a sheltered site (to avoid the flower spikes getting blown over) and a free-draining soil with plenty of sunshine.

Allium can also be grown in containers and like deep pots. Use a soil-based compost, but make sure the compost does not dry out. Remember to feed with liquid fertiliser during the growing season. For garlic, you can place a number of individual cloves in a pot (tip up) in the spring and place on a sunny window sill. Some Alliums, such as Tree onions, grow too tall for most containers.

How do you grow Alliums?

You can grow Alliums easily from seed but they require a temperature of 19 Deg C to germinate. Therefore, if sowing outside, wait until late spring or when the soil feels warm on the back of your hand. If you want to get ahead, then you can sow in plug trays with bottom heat in early spring. Sow about 10-15 seeds per 3 cm cell and plant out when the last frosts are over. Watch Jekka's Video on How to Sow Seeds for some tips.

When planting out, dig over the soil and remove any weeds. Avoid planting into freshly manured soils which may be too nutrient rich. Keep newly transplanted plants well-watered in the spring and in the summer make sure they do not dry out.

Every few years in the spring, you can lift clumps, divide and replant in 6-10 bulb clumps 15 cm apart.

Alliums die back into the ground in winter and so it is sometimes useful to mark the soil to know where they have been planted so to avoid disturbing them when preparing the gro und for new plants.

What pest & disease to look our for?

The onion fly is the curse of the onion family especially in late spring and early summer. The way to try and prevent it is to take care not to damage the roots or leaves when thinning the seedlings and also not to leave the thinnings lying around, as the scent attracts the fly.

In addition, alliums are susceptible to white rot and can also suffer from rust. With both diseases, it is essential to cut back diseased growth immediately and burn it. DO NOT COMPOST. You should also avoid using the ground for garlic or chives again.

How to harvest Alliums?

It is easiest to harvest Alliums as needed with scissors, cutting them back close to the base of the plant. The more regularly they are cut, the newer leaves they will produce. Jekka ’ s tip is to remove the flowering stem before flowering to increase leaf production.

The culinary uses of Alliums

Whole garlic bulbs can be roasted and the longer garlic is cooked the milder and sweeter the flavour. The number of recipes that use garlic is endless from garlic mayonnaise to roast chicken with garlic. We are never without garlic at home.

Chives are also another staple from the Allium family and fresh chives are deli cious as a garnish or flavour and go particularly well with potato and egg add liberally to sour cream as a filling to jacket potatoes. The flowers are also edible and add a distinctive onion flavour and colourful decoration to salads.

Wild Garlic is becoming increasingly popular and Instagram is filled with people foraging wild garlic for soups, salads or for inclusion in sourdough. Don ’ t forget the flowers are also edible. As with all foraged foods please ensure what you have picked is what you think it is.

Jekka’s favourites

Fancy growing some Alliums? These three are Jekka's favourite that can be grown from seed click on the links to see more.

Want to know more?

For advice on growing and maintaining herbs, check out Jekka's How to Grow Herbs videos and ‘Jekka’s Seasonal Tips’ blog series, which includes what to do in your herb garden in early spring, late spring and autumn & winter.

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