Allium is very easy to grow! Just plant and go!
Allium is best planted in the fall when it gets cold. Plant them any time before the soil has frozen. Pick an area with full sun and good drainage, but alliums can grow in partial shade as well. Allium can be grown in areas where pests normally nibble on flowers, as they taste unappealing and usually are too fragrant.
Make sure that your soil is well worked, up to 6-8” down and utilize a good bulb fertilizer while planting. Plant your bulbs up to 3 times their diameter, with the pointy end up, 4-12” apart. Giant alliums should be up to 24” apart. You may see some growth in fall (it looks like a standard onion), or you may not see top growth until spring. Allium can remain dormant all winter.
Once you start to see the flower for allium, watch for drooping. If this occurs, your allium flowers won’t open entirely. Consider staking the flower stem to keep it upright. Your allium does not require mulching, but you can certainly add mulch to retain moisture and prevent weeds. During the winter, not much water is needed, and too much can lead to bulb rot. While growing, keep watering even to ensure continued growth.
When flowering is finished, allow the flower cluster to die back before trimming. Leave the foliage in place until it turns brown and dies. Allium should come back year after year, and only needs to be divided every 3 years or so.