Warm winter month forces flower bulbs into action

During unseasonably warm periods, early bulbs might sprout prematurely, especially those planted with a southern exposure, close to a house or garage.

The Chicago Botanic Garden has on occasion had snowdrops in flower in late February in similar locations. The first greenery to show is foliage, with flower buds appearing much later in the bulb's growth.

Subsequent cold weather might damage the edges of the foliage, but unless the flower bud has appeared, it will not affect the future flowering or health of the bulb. A few of the small early bulbs can tolerate a bit of frost. They include winter aconite, snowdrops and glory-of-the-snow.

You may be seeing bulb foliage that came up during last December's warm weather with frost damage. This is nothing to be concerned about.

• Branches with interesting foliage, as well as flowering branches, can be forced. Prune those branches that are not essential to the plant's basic shape or save branches from your winter pruning. Branches should be at least a foot long, full of fat flower buds and cut on a day above freezing.

Cut the ends at an angle and put the branches into water in a cool room, out of direct sunlight. When the buds color up or the foliage begins to unfurl, arrange the branches in a vase and display them in a cool room, out of direct sunlight.

Good choices for forcing this month include: serviceberry (Amelanchier), magnolia (Magnolia), flowering quince (Chaenomeles), forsythia (Forsythia), crabapple or apple (Malus), flowering pear (Pyrus), flowering cherry (Prunus), spring-flowering witch hazel (Hamamelis vernalis) and redbud (Cercis).

The spring-flowering witch hazels in your garden may have already flowered due to the warm weather over the course of winter.

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