Best known for its edible varieties—onions, garlic, chives, shallots and leeks—Allium also includes hundreds of ornamental species. Far too interesting to be left in the vegetable patch, various cultivars are in bloom May to July and, as spring bulbs, must be planted in fall. The tall-growing species, standing like sentries with big, round heads, provide wonderful contrast to other shapes usually found in perennial borders; dwarf species are well suited to rock gardens.
While some allium flowerheads are just a couple of centimetres wide, others can be ten times as large. These perennials range in height from 15 centimetres to more than a metre, with flower colours of white, yellow, blue, silvery pink and mauve. Their leaves (either round and hollow or flat and strap-like), although attractive when they first emerge, can become untidy later in the season. Plant them among other perennials or annuals such as roses, irises, poppies, anemones or petunias to help screen the leaves.
Alliums are long-lived and do not appeal to deer, squirrels, rabbits, mice or chipmunks. Flowers can be left on the stalk to dry or, if cut early, will last up to three weeks in water. The slightly garlicky smell they emit when cut disappears once put in water.
Of the more than 450 species known, only a handful are widely cultivated. Most, including those on page 2 (save one), are hardy to Zone 4, even Zone 3 with mulching and/or snow cover.
- Plant bulbs in fall (once ground temperatures have dropped below 16°C) at a depth three times their height: about 15 centimetres for larger bulbs, 10 for smaller ones.
- Alliums prefer well-drained, neutral or alkaline soil and adequate moisture (about 2.5 centimetres per week).
- Space about 30 centimetres apart, as most bulbs will reproduce, gradually forming clumps, with each bulb producing its own flower.
- Plant tall varieties in a well-protected spot; with their large, heavy heads on tall, narrow stems, they’re easily blown over.
- For the best show, plant in groupings of three to five.
- Mulch generously in areas where frost and snow are threats.
- Fertilize three times with bone meal or any good garden fertilizer: once when planting, once just after they emerge and again right after flowering.
(The allium shown above is a 'Globemaster'.)