Could I plant allium seeds in the fall? How deep should they be planted? Will they flower next spring?
Alliums are in the Amaryllis family. The allium genus contains hundreds of different species including are large variety of garlic, leeks, onions, chives, shallots, scallions and the more ornamental flowering alliums including the giant Asian alliums and, my favourite, Allium cristophii- or Persian onion.
Most edible alliums require spring seed planting- especially in regions with cold winters, like here in Toronto. Fall planting is risky as the seeds don’t like to sit in wet soils. When Toronto experiences mild winter days- when the snow thaws, the seeds often either rot or germinate only to be frozen by the next cold spell.
Ornamental flowering alliums are usually planted as a bulb, in the fall, at a depth of 4-6 inches. In Toronto it is a good idea to add several inches of mulch over the soil to protect the bulbs. Mulch helps to insulate the soil around the bulbs and stabilize soil temperatures.
If you are planting flowering allium bulbs, like the popular Allium aflatunense ‘Purple Sensation’ , or Allium ‘Globemaster’ you may not get flowers the first spring, or the flowers that bloom may be small. By the second spring you will get big beautiful blooms, if they are planted in well draining soil, rich in organic compost.
Try to select large, healthy bulbs to plant in the fall to increase the chances of them flowering in the spring.