How to Grow Allium – Flower Care Guide

Want to learn how to grow Allium? This Allium care guide will show you how. Growing Allium is a relatively straightforward process. Once you know a few key things you will be able to fill your garden with these attractive flowers. A long lasting plant, alliums will bring color and definition to a range of planting schemes from late spring until mid summer.

Part of the amaryllis family of plants, Alliums are related to common vegetables such as elephant garlic and onions. They also make great cut flowers and their seed pods can be sprayed for attractive Christmas decorations.

This Allium guide will take you through everything you need to know about Allium flower care.

Tall and elegant alliums are a stately addition to any garden. Allium can be used to add structure or definition to borders. The spent deadheads of the allium then give way to attractive seed heads, providing interest long after the blooms are spent. 

Varieties of Allium

There are over 700 different Allium varieties commercially available. This means that there is plenty of choice for your garden.

Large varieties such as Globemaster will produce strong stems reaching up to 4 ft in height. These will support large white globe shaped flowers. Smaller varieties such as Purple Sensation will reliably bloom to produce attractive purple flowers roughly the same size as a tennis ball. Like many other alliums these will bloom year after year.

For late season color Ozawa Allium produces pink flowers during the fall months. Continuing to bloom while other perennials have faded, Ozawa Allium will continue to attract pollinators to your garden until late October.


As well as being attractive, alliums are also popular with pollinators. They can provide a reliable supply of food late into the fall, when other sources are scarce.

Finally the Schuber Allium is a small, compact variety. Reaching no more than 8 inches in height its bright pink flowers resemble exploding fireworks.

When selecting the allium or alliums for your garden, the choice on offer can feel overwhelming. Try to keep in mind how much space you have available. You should also consider your climate, soil conditions and what purpose you want the plant to serve. All these factors can help you to narrow your choice and select the perfect flower.

Planting Alliums

Before we discuss Allium care, we first need to ensure that the bulbs are planted correctly. This may sound simple but many of the problems people encounter when growing Allium are because they are planted incorrectly.

Alliums are hardy to USDA zone 4. They will grow best and bloom in zone 4- zone 10 but gardeners outside of this zone range can also grow Allium flowers successfully.


As long as you can provide a few basic requirements, Allium care is relatively simple. Planting the bulbs in well drained soil in a sunny position will give them the best possible chance of thriving and reaching a full bloom. 

Allium likes to grow in full sun positions. They also prefer well drained soil. If your soil seems heavy try working some grit or gravel into the soil before planting.

Alliums, and other spring flowering bulbs, are best planted in the fall or early winter. Flowering bulbs are generally less sensitive to extreme temperatures because the soil provides some insulation. In milder climates you can continue planting alliums until mid December or as long as the soil remains workable.

Spacing Allium Flowers

Like other aspects of allium flowers care, spacing depends on the variety of allium flowers you are growing. Larger Allium varieties, such as Globemaster, will require spacing to 11-14 inches. Smaller varieties will take up less room, requiring a spacing of between 3-6 inches.  It is important to correctly space your allium bulbs. If the bulbs don’t have the room they require the Allium plant will become stunted and may struggle to flower.

Correct planting is a key part of Allium care. Properly spacing your bulbs, and planting them to the correct depth, ensures that they have room to grow. It also ensures that there is enough space for fresh air to circulate, significantly reducing the chances of the plants becoming diseased. 

Similarly try to plant to the required depth. Planting deeply helps to improve the perennial habit of bulbs. Again smaller or medium sized varieties will thrive in a planting of 3-6 inches. Larger varieties will need more depth, 11-17 inches depending on the variety.

To learn the exact spacing and depth your Alliums require read the label or information on the plant packet before you begin planting.

Planting Allium Bulbs

Alliums can be planted into the ground or into a container.

Plant Allium to the correct depth. If you are unsure try to plant to a depth of at least twice the bulb. If you are planting in containers ensure that there is space for a layer of soil about 1.5 inches thick between the bottom of the container and the bulbs. Cover with soil and firm down gently.

If you are planting into poor soil apply a potash feed in early spring. Potash feeds encourage the bulb and roots to form. It also helps to prolong the life of the bulb. Potash feed applications will benefit all spring flowering bulbs.

While feeding is not necessary for correct Allium care, applying a potash feed can help to encourage the bulb to flower. This is particularly vital in the bulbs first spring.

Allium Flower Care

Alliums may look like a majestically high maintenance plant, but Allium is in fact refreshingly easy to care for. Here is everything you need to know about Allium flower care.

Watering and Feeding

Watering is essential. The bulbs will require regular watering. If you want to save on your water usage why not try harvesting rainwater? You can then reuse this in your garden.

Regular watering is vital during dry spells and when the Allium plants are in flower. Alliums growing in containers will also require more frequent watering.

Regularly watering the plants is a key requirement for good Allium flower care. Plants growing in dry conditions, or in containers, will require more regular watering. After a period of heavy rainfall it is best to wait for the soil to dry before watering. 

You won’t need to feed plants if you regularly amend your soil. Flowers in poorer soil will also benefit from a regular application of balanced fertiliser. This should be applied when the flowers begin to set. If you don’t want to buy chemical fertilizers, you can make your own liquid fertilizer. These can be just as effective as purchased fertilizers.

Finally mulching the beds in early spring with an organic matter will give the plants an extra boost. Mulch also helps the soil to retain moisture. This means that the bulbs are less likely to dry out.

Pruning

Alliums will only flower once a year, typically in late spring to early summer. If you have cared for it properly, starting late spring to early summer you should see a long lasting bloom. Once spent the dried heads can also provide an attractive feature in your garden.

While some gardeners choose to deadhead spent alliums, others opt to leave the seed heads in place. Allium seed heads create an interesting shape, adding a new fascination to your garden beds. While deadheading helps the plant to conserve energy, leaving the seed heads in place is not detrimental to correct Allium care. 

Alternatively you can cut the heads away once flowering in concluded. Don’t cut the plant back completely. The leafy foliage should be allowed to remain in place. This encourages the plant to store energy in the bulb meaning that it will come back strongly again the following year.

Any withered or damaged leaves should be removed as quickly as possible.

Bulb Division

Occasionally Allium will require you to make bulb divisions. This can be either when offsets or rhizomes form. If you don’t divide plants they can become overcrowded. This can stunt growth and lead to a diminishing in the plants flowering habit.

Bulb forming Alliums are slow to form. They will appear on the original bulb. To divide these, once flowering has finished life the bulb and remove the offset. The bulb and the offsets can be replanted immediately. Bear in mind that offsets can be slow to grow. This means that it will be a few years before they begin to flower.

Rhizome forming Alliums are more noticeable. When the club begins to look crowded lift and divide. This can be done at any time of the year but is best done in the fall when the bulbs are dormant.

Common Pests and Problems

Allium is largely pest and problem free. As it is related to onions, and discharge a similar aroma, many larger pests and rodents tend to avoid them.

In wet conditions the plants may develop fungal diseases such as downy mildew. However as long as you have cared for it properly this is unlikely to occur. Leaf miner may also strike. But the damage is largely cosmetic so isn’t a major concern.

You will need to protect young and emerging plants from slugs and snails. Both chemical and organic solutions, such as coffee grounds, will work effectively.

Alliums as Companion Plants

Companion planting is a great way of encouraging plants to grow without using chemical methods. Alliums can thrive in a number of different schemes, from natural planting schemes to herbaceous borders. They will happily grow in your garden without inhibiting any other plants.

Alliums are an attractive and easy to care for addition to any garden that blooms in the summer. Capable of fitting into a range of planting schemes Alliums provide both early and late season interest to your garden through the summer. 

Decorative ornamental onions, alliums are more than just a pretty flower. A tough garden plant, Allium care is surprisingly easy. Meaning that with just a few basic steps you can enjoy their distinctive flowers from late spring through most of summer, typically till mid to late summer.