How to enjoy your flowers longer

When buying cut flowers, I look closely to make sure the flowers are fresh. Petals that show browning at the edges or are falling off are signs of being past their prime, with a shorter life span in your home.

It is also important to properly handle any cut flowers purchased at this time of year to prevent cold damage. Warm up your car when transporting the flowers, especially if outdoor temperatures are below freezing. The flowers should not be allowed to sit in a cold car.

To keep cut flowers fresh, place them in room-temperature water as soon as possible. With a sharp knife or pruners, make an angled cut and remove at least 1 inch from each stem. Ideally, make this cut while the stem is under water. Cutting on an angle increases the surface area for water intake.

Add floral preservative to the water in the vase. Most preservatives contain an acid (to neutralize alkaline tap water) and an ingredient to discourage bacteria. Remove all foliage below water level.

Cut flowers prefer a cool, humid environment and should be kept out of bright light and away from heating vents. Do not place cut flowers close to a bowl of fruit or vegetables, because the ethylene gas emitted by ripening fruit can damage the flowers, as can cigarette smoke.

If healthy cut roses suddenly develop drooping heads, it may be due to air bubbles trapped in their stems. Float the entire stem in a sink full of warm water. Trim another inch from the stem, cutting on an angle below water level. Try to gently straighten the drooping flower head as the flower and stem continue to float.

Keep the cut end of the stem under water for at least a half-hour. When the flower head hardens to a straightened position, the rose stem may be placed back in the vase.

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