Spring bulbs can withstand some chilly temperatures, unlike many varieties of annual and perennial flowers. Tulips and daffodils are plants that die back to their underground bulbs every year. After resting beneath the soil during the winter months, the bulbs produce new shoots as the soil begins to warm in early spring. Although they winter over in climates as cold as Zone 3, a hard frost can damage these spring bulbs, depending on their stage of growth.
The exposed foliage of most varieties of tulips and daffodils can withstand temperatures down to -1.67 degrees Celsius, when light frosts occur. Hard frosts that occur when temperatures dip below -2.22C can damage the exposed stems, leaves and flowers, eliminating the flowers for that season.
Winter temperatures that damage the bulbs result in death of the plants. While most tulips and daffodils survive in cold climates with long winters, some tender varieties, such as paper whites won't survive extreme cold. Commercially available bulbs usually contain hardiness zone ratings. Make sure you only plant bulbs rated for your climate.
Early spring frost won't affect the health of the underground bulbs, however. Spring bulbs usually start growing before the final frost of the season. Tulips and daffodils frequently begin growing before the snow completely melts in some areas. This early growth exposes them to possible frost damage when temperatures warm up then dip down into the 20s or the teens. Frost damage causes blackening and wilting on the affected vegetation. Depending on the extent of damage, some plants recover and go on to produce flowers the same season.
Temporary covers can help protect growing tulips and daffodils from hard spring frosts. Draping a thick piece of burlap or a heavy blanket over a post driven next to the growing plant provides a layer of insulation. Piling up fresh straw around the exposed foliage can also help limit frost damage. Remove the insulating covers and mulch as soon as the risk of frost is over. This may require lifting and replacing the insulation for several days in a row. Although this method may help protect tulips and daffodils from some damage during cold nights, it won't prevent damage during extreme cold spells.