The Allium family includes much more than onions and garlic. Over 850 species of plants exist in the Allium genus, some of which are popular as flowering bulbs. White Flower Farm reports that the various Alliums bloom in early summer and that many garden pests avoid the areas in which you plant them because of the bulbs' pungent smell. The Alliums have similar round flower heads consisting of many small flowers ranging in color from white to deep scarlet. Some, like the Allium bulgaricum, have pink and white bell-shaped flowers in heads the size of a baseball.
Prepare your planting area in a sunny area by digging any type of compost into the soil in fall. Use two 5-gallon buckets full of compost for every 10 feet of garden row, and mix it well with your topsoil.
Dig holes 2 to 10 inches deep with your trowel, depending on Allium variety. Plant larger bulbs deeper than small bulbs. Drop one Allium bulb into each hole. For most varieties of Allium, leave up to 12 inches between planting holes. September and October are the best months to plant Allium bulbs.
Water the soil well by setting a sprinkler in the area for at least 30 minutes. After your initial watering, keep the soil moist by watering at least once a week.
Fertilize your Alliums with a balanced fertilizer having an N-P-K ratio of 8-8-8, immediately after you plant them. The University of Maryland recommends using 2 to 3 lbs. of plant food for every 100 feet of row. Use less depending on the size of your Allium bed. Fertilize older bulbs with the same type of fertilizer in spring, when shoots appear above ground level.
Control aphids, which are one of the only insect pests that bother Alliums, by spraying your plants with insecticidal soap. Repeat your application every few days until all signs of this insect disappear.
Divide Allium bulbs every 3 to 4 years if they become crowded or make more plants than you want. Dig up the large clump of underground bulbs, separate them, then replant individual bulbs as you did when you first planted your Allium.