This Month in the Garden: Alluring Alliums!: Fall Planting, Care & Maintenance

Allium Planting, Care & Maintenance

Allium is a genus consisting of over 850 species of plants which includes ornamental forms used for gardening and those cultivated for food, such as onion, garlic, chives, scallion, leek and shallot. Allium can be found growing in the Northern Hemisphere, with a few species occurring in Chile, Brazil and tropical Africa. Originally classified by Carolus Linnaeus in 1753, allium were considered a plant with valuable attributes. By the late 1800’s Russian botanists began collecting species of Allium from Central Asia and introduced them to horticulturists through the Imperial Botanical Garden. Soon after, Britain had heard of this new family of garden-worthy plants and continued to expand the number of available selections through hybridization. Allium has gained increased recognition over the years for its ornamental qualities and was named bulb of the year in 2016 by the The National Garden Bureau and the Perennial Plant Association has voted Allium 'Millenium' as the Perennial Plant of the Year for 2018! 

Globemaster Allium

Allium (Ornamental Onion) are hardy in USDA hardiness zone 3-9, depending on the species, and prefer to be grown in full sun. Allium are drought tolerant and should be planted in a well-drained, slightly acidic soil (pH 5.5-6.5) which is kept on the drier side. Bulbs should be planted in early autumn (September-November) at a depth of approximately four times the diameter of the bulb. Smaller growing Alliums should be planted at 3-4 inches (8-10 cm) apart, while taller species need at least 8 inches (20 cm) between the bulbs. A sprinkle of bone meal around the bulbs at time of planting (but not near the root) will give them a good start. As mentioned, Allium bulbs are best planted in autumn (by late November) but can be planted in late winter/early spring for late May/June blooms. Flowers may not be as large in the first season, so the application of a balanced fertilizer once foliage emerges will encourage plant strength and blooms.

Allium Mont Blanc

Allium bloom time starts in late spring into early summer and plants are available in a wide variety of sizes and colors, ranging from the white Allium (example 'Mont Blanc'), to blue (Allium caeruleum), yellow (Allium flavum) and purple (Allium giganteum). Plant heights vary between 10 inches (25.4 cm.) and 50 inches (127 cm.) and produce rounded blooms that form at the top of a leafless stalk. Many Allium have basal leaves that commonly wither away before or while the plants are in flower, but some species have persistent foliage throughout the season. Generally, species that hold onto their foliage typically bloom later into fall and form dense clumps rather than individual blooming plants. Varieties that lose their foliage tend to form individual stalks with larger blooms. Allium can be planted as seed, but is best planted as bulbs, which vary in size between species from the smaller 2–3 mm bulb to the larger 8–10 cm bulb of larger blooms. 

Allium Globemaster (Allium giganteum)

Allium require little to no maintenance and are mostly pest and disease free. They are members of the onion family, so the foliage and blooms and are not preferred by deer, rabbits or squirrels. They are also an attraction to butterflies, bees and other pollinators. Removing spent blooms after blooming can encourage plants to store more energy for the following year, but it is not necessary, and some gardeners prefer to leave dried blooms for the remainder of the summer for interest and to encourage re-seeding. There is no need to dig Allium up in the fall, since they do not require any dividing, but can be moved to other locations at that time.

Allium caeruleum Blue

Allium have a wide variety of uses in the landscape and can be planted among evergreen or flowering shrubs and along with other perennials. This versatile plant is easy to plant and maintain and will bring years of enjoyment to your landscape. The possibilities are endless!

Photo Credit: Longwood Gardens (Flowering time Left to Right: Late Spring-Early Summer)

As Always...Happy Gardening!

Author: Lee@A Guide to Northeastern Gardening, © Copyright 2018. All rights reserved