Tips for autumn planting of your flowering bulbs

Most bulbs should be planted after a hard frost (mid- to late October) but before the ground freezes. Fall-flowering bulbs such as autumn crocus (Colchicum) should have been planted as soon as they arrived in early to mid-September.

Bulbs rarely look good alone or in rows. Plant them in clumps or drifts. Bulbs such as daffodils and Siberian squill can be naturalized, or planted to look as if they are growing wild. One way to do this is to toss handfuls of bulbs and plant them where they land.

Small bulbs such as crocus should be planted in large groups of at least 30 to 50 so they are more prominent in the landscape.

Incorporate bulbs into the perennial border in groups of seven to 15 bulbs or more. Consider the management of bulb foliage when planting in perennial borders as the bulbs need to go dormant before cutting back the foliage. Lots of browning bulb foliage can be intrusive in a perennial border, so choose ones with less foliage or blend carefully with larger perennials.

Proper placement is also important for success with spring-flowering bulbs. They prefer moisture in early spring and fall and dry conditions in the summer when they are dormant. They do not like wet sites or heavy clay soil.

If your garden soil is heavy with a high clay content, plant the bulbs higher than normally recommended. In general, plant bulbs at three times the diameter of the bulb.

Daffodils are one of the hardiest, most adaptable and pest-resistant bulbs for Chicago-area gardeners. They naturalize beautifully and are available in many sizes and bloom times. Proper selection of varieties will give three to five weeks of constant bloom. Deer, squirrels, chipmunks and rabbits do not eat them.

Ornamental onions also will not be eaten by animals. Tulips are a deer and rabbit favorite. In my garden, squirrels and chipmunks have left winter aconite and snowdrops alone while eating all of the crocus.

Crocuses are ideal bulbs for rock gardens or for planting beneath tall trees. They may be scattered in lawns, but their grasslike foliage must remain intact at least six weeks before being mowed at a short height for best results long term. Crocuses, which are planted shallowly, are easy targets for chipmunks and squirrels and might require repellent products or a chicken wire screen placed directly over them at planting time. Blood meal sprinkled on the ground after planting may help repel animals.

• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.