The lemon blossom is the flowering of the lemon tree. Lemon has a white flower with a yellowish base and five fragrant petals. Lemon trees are among the most cold-sensitive trees and they flower and bloom only with proper care. The lemon tree needs at least six hours of sun exposure a day to be healthy and produce flowers. In cooler climates, a potted lemon tree should be kept in the house during the cold months.