Growing And Caring For Allium (Ornamental Onion)

Growing And Caring For Allium (Ornamental Onion)

Emma DowneyByEmma Downey
Updated on 8/13/2022

Ornamental onions have several close cousins that absolutely deserve a spot in your flower garden. The vast majority of us do not consider onions to be beautiful plants; however, onions have several extremely close cousins that deserve a place in your flower garden. The flower heads of ornamental alliums with a high growth rate are spherical and have hundreds of blooms arranged in the shape of stars. These alliums may reach a height of several feet and have a rapid growth rate. When the leaves of these plants are broken, they release an odor that is barely evocative of onions. This smell is released when the leaves are crushed. These plants, however, are not suitable for human consumption.

Ornamental Onion

The colorful, globular flowers produced by decorative alliums won't add any heat to the meal you make, but adding these plants to your yard will be very much appreciated. These plants are particularly hardy since they can go for extended periods without any form of moisture and tolerate a large amount of frost. Even rodents and deer don't bother them, who may use many different kinds in other gardens. It is advised that you plant your allium bulbs in the fall for the most outstanding results.

How To Take Care Of And Grow Violaces

  • Botanical Name: Allium
  • Common Name: Ornamental allium
  • Plant Type: Bulb or rhizome
  • Size at maturity: 3-10 inches broad and 3-4 feet in height
  • Sun Exposure: Full sun
  • All types of soil are acceptable, but they ought to drain adequately.
  • Soil pH: 5.5-6.5
  • Bloom Time: Primarily Spring, however, some plants bloom in the Fall as well
  • The colors pink, purple, yellow, white, and green are used for the flowers.
  • Hardiness Zones: 4-10 (USDA)
  • Originating from: the Middle East
  • Toxic potential: somewhat hazardous to human health; harmful to canine and feline animals

Ornamental Onion Care

A few species of alliums, such as the common chive (Allium schoenoprasum), grow their progeny in the form of underground rhizomes rather than bulbs. However, most alliums generate their offspring in the form of bulbs. There is a chance that they will never mature into a bulb of any kind, which is a distinct possibility. A common characteristic of the leaves of an allium is their elongated, strap-like shape. Some, like the corkscrew allium, maintain their beauty throughout the season thanks to their blue-green hue, which complements the blooms. Most early blooming alliums have foliage that has a predisposition to die back early since the plants prefer to stay dormant for the whole summer. That is because early blooming alliums produce flowers earlier in the season.

The blooms develop in clusters and are most commonly recognized as having the shape of a spherical pom-pom. However, they can also assume the form of a star, a cup, a semicircle, or hang down like a pendulous cluster of flowers. A significant amount of morphological variation is seen among plants belonging to the allium. Drumstick alliums only grow to be about one foot tall. They have flower heads that are only one inch in diameter, but large 'Globemaster' alliums can reach heights of up to four feet and flaunt enormous globes with flower heads that are anywhere between eight and ten inches in diameter. Drumstick alliums are the smaller of the two types of alliums.

Ornamental Onion Care

The great majority of allium bulbs have a fast growth rate, and their blossoms can be seen throughout the spring or early summer, long after those of the earliest spring bulbs have faded and died. That is because allium bulbs bloom later in the season than other types of spring bulbs. However, a few cultivars bloom considerably later in the season than others, and some continue to do so even far into the fall.

When the blossoms poke through other plants, whether those other plants are low-growing mats like hardy geraniums or shrubby roses, they create a charming aesthetic that is hard to resist admiring. Their appearance is rounded and round, giving the impression that they are smiling. For example, peonies, irises, and catmint are some of the late-spring flowers that thrive when the color purple is used because of its capacity to harmonize with other types of flowers. This shape may be quite effective when combined with other plants of a comparable height, such as foxglove or monarda.

Even before the plants have developed flowers, early-blooming alliums can undergo a considerable loss in the quality of their leaves. That can happen quite a while before the plants generate flowers. They bloom quickly, the most critical drawback of early-blooming alliums. It is strongly suggested that you try to hide the leaf behind a more substantial plant if this is at all possible; daylilies are an excellent option for accomplishing this goal.


If you want your alliums to have the most stunning blossoms and be in the best possible condition, you should position them in an area where they will be exposed to sunshine for the entirety of every day. They can survive in locations that get some shade; however, because so many of these plants have short growing seasons, it is ideal to expose them to as much direct sunshine as is feasible.



The pH range in which alliums thrive ranges from 5.5 to 6.5, with 5.5 being the most suitable of the available options. On the other hand, the soil's drainage capacities are considerably more valuable than the earth's pH. That is because drainage is essential for plant growth. When the bulbs are in their dormant stage, it is especially vital to ensure that they are not allowed to remain in too damp soil. If they are allowed to stay wet for a highly extended period, their condition will begin to degrade. Take the time before planting to improve the soil's drainage by incorporating a sizeable amount of organic matter. You won't have to worry about the bulbs suffering from a deficiency in the amount of water they receive.


Because alliums only need a tiny sprinkling of water once every few days, it should be OK for you to grow them even if you live in a region that receives a lot of precipitation. Other than that, you should only need to water the plant once every three to five days.

Temperature And Relative Humidity

The hardiness of alliums varies depending on the type being produced and the growing environment; despite this, the vast majority of alliums are well-suited for cultivation in USDA hardiness zones 4-10.

Temperature And Relative Humidity


If you are consistently working to enhance the quality of your soil, it is feasible that you won't even need to feed them at all. If, on the other hand, your soil is less than ideal, supplying your plants with a small amount of balanced fertilizer just before they begin to set flowers can assist them in replenishing all of the energy used while they are blooming. That is because blooming requires a lot of plant energy, and balanced fertilizer contains the correct ratio of nutrients.

Ornamental Onion Varieties

  • 'Drumstick allium': (Allium sphaerocephalon) Their flower clusters, which are only one inch across and bloom in the early summer, begin their lives with a greenish hue but later take on the appearance of red clover. The most significant way to show them off is to let them wander freely about the garden so they may take you by surprise by poking their heads out from behind other plants.
  • The meaning of the term "corkscrew allium" (Allium senescence ssp. montanum var. glaucum) The popular name for this allium comes from the bluish-green leaves that curl and turn, and they give the plant its distinctive appearance. Since it develops from rhizomes and not from bulbs, you will probably find this one in the department of garden centers dedicated to perennials. The flower heads of this lavender plant are flattened balls around 2 inches in diameter, and they bloom from the middle until the end of summer.

Ornamental Onion Varieties

  • "Globemaster" refers to a super-sized variety of flower stalk that can grow to a height of between three and four feet and is crowned with blooms that cluster together to form a ball between eight and ten inches in diameter. Another towering mountain that belongs to this genus is Mount Everest. It's not quite as big as the Globemaster, but it blooms in a beautiful creamy white color.
  • The meaning of the term "Japanese onion" is as follows: (Allium thunbergii) They form more of a mop than a spherical globe, and their flower heads, which are only about an inch in diameter and pink in color, bloom in the early fall. Some of the varieties you should seek are Ozawa, which has more giant flower heads that are a deep purple color, and Alba, which has white florets that are formed like cups. This allium does not create bulbs but grows from underground stems known as rhizomes, which may purchase in pots.
  • 'Nodding onion': (Allium cernuum) This species produces flower heads that are shaped like mop tops and come in a variety of lovely pink and purple colors. The length of the flower stalks ranges between two and three feet. That is one of the alliums most adaptable to a broad range of conditions, and it can even be grown well in partial shade.
  • The flower stalks of the 'Purple Sensation' variety grow to around two feet and are crowned with a globe of brilliant purple blooms measuring two and four inches in diameter. The Purple Sensation bulb has a reputation for having a long lifespan. Still, its leaves have a propensity to turn yellow or brown rather quickly, which can be distracting from the magnificent blooms it produces.


  • 'Schubert allium': (Allium schubertii) There is something about the bloom heads of Schubertii alliums that reminds one of a fireworks show. Even when they become less noticeable, the explosive appearance they formerly had is still present. The tumbleweed onion is another name that is commonly used for Schubertii.


The same flower will not open on an allium plant more than once. After the plant has finished producing flowers, cut the flower stems to the ground so that it may redirect its attention to the bulb where it will store energy. However, the dried flower heads are just as gorgeous as the living blooms, and many gardeners choose to keep them standing.

Propagating Ornamental Onion

The autumn season is the ideal time to plant alliums, which will mature into bulbs in the spring. When planting bulbs, it is advised that the planting depth be anywhere from two to three times the diameter of the bulbs. (For instance, if you have a bulb with a diameter of two inches, you should plant it between four and six inches deep.) After you've planted them, you need to be sure to give them a lot of water, and then you need to keep your fingers crossed until the following spring.

allium plant

Alliums that form bulbs have a somewhat slow reproduction rate; nonetheless, they will eventually develop small offsets on the original bulbs or even on the flower head. These little offsets will continue to grow on the parent bulb. After the plants have finished their cycle of producing flowers, you will be able to dig out the bulbs from the ground and prune away the offsets. These may be transplanted straight immediately, but it may be a few years before they produce blooms in their new homes.

It is entirely up to the gardener to determine when who should plant the alliums propagated by rhizomes. When you go to the garden center in the latter part of the summer, it is conceivable that you will not be able to find the varieties that bloom in the fall until much later in the season. It is feasible to pluck the plant and divide it into two parts if it appears that the cluster of rhizome-forming alliums has become too congested. You shouldn't wait until the plant has lost its vitality in the core before dividing it; you should do so as soon as possible.

Common Diseases And pests

To a similar extent as their edible counterparts, decorative onions do not attract a significant number of insects or other kinds of pests. Animals like deer and rodents will avoid them like the plague when they are around.

Common Diseases And pests

They are sensitive to a few fungal diseases, such as downy mildew and rot; nevertheless, these conditions do not provide as much of a barrier in a flower border as they would in a vegetable garden if they were present. To solve the issue, you will need to remove any infected bulbs and stop watering the plants from above.

When it comes to insects that might be a nuisance, be on the watch for snails, slugs, and the ornamental onion leaf miner. On the other hand, given that the foliage does not stay on the plant for a significantly extended period, there is no need to be concerned about the appearance of any cosmetic damage to the leaves.