The good news is that flowering bulbs are remarkably resilient. Most will not be fazed by limited periods of cold weather, says Steve Zwiep, Parks Department supervisor for the city of Holland, Michigan, home of the annual Tulip Time Festival. “We’ve had snow a foot deep and packed around the tulips. When the snow melted, the tulip buds were fine and ready to go,” Zwiep says. The risk of damage is greatest, he explains, when the plants are blooming.
Before the buds open, both daffodils and tulips are fairly immune to the cold, but open flowers are more sensitive to frosts and freezes. “Freezing temperatures overnight with warming during the day usually doesn’t cause any problems,” says Zwiep, who has grown literally millions of tulips over the years, both in his family’s greenhouse business and for the city of Holland. “Once [tulip] stamens start showing, the flowers become sensitive to prolonged frost and may be damaged by the cold.”
By “prolonged,” he means round-the-clock low temperatures lasting for several days. He recommends covering small areas of blooming flowers with a sheet (supported by plant stakes to avoid breaking stems) during the nights when such conditions occur. “You can also use a sprinkler to spray water on the flowers to prevent injury, as growers in Florida do to protect the blossoms on fruit trees,” he adds.
The Holland, Michigan, 2011 Tulip Time Festival will be held May 7 to 14 and will feature parades, celebrations of the city’s Dutch heritage and culture, and 6 million tulips.