A double flower is a plant in which extra petals are present, giving blooms a full or doubled appearance. Prized since ancient times, double flowers are somewhat difficult to cultivate, as many are sterile and must be regrown from cuttings rather than simple propagation. Genetic studies have shown that a double flower is the result of a specific genetic mutation, one rarely found in the wild.
Certain types of flowers are more likely to have a double bloom than others. Roses, camellias, peonies, and carnations all commonly exhibit double flowers. To determine if a flower is a double flower rather than simply a lot of petals, look carefully at the petal structure of a bloom; if it appears to have a fully structured flower within another fully structured flower, it is likely a double flower.
Most modern hybridized roses are likely to show a double flower, due to genetic manipulation through breeding. Old World roses often have a single layer of petals and are quite delicate in nature, while modern tea varieties typically feature layer upon layer of petals, making for a fat and full bloom. When searching for rose plants, look in the scientific name for the term flore pleno, usually abbreviated to Fl. Pl., to indicate that the rose has a double flower. The term comes from the Latin words for “full flowered,” and plants bearing the term may produce at least some double flowers.
The rare occurrence and breeding problems associated with double flowers has been a mystery for thousands of years. Only as genetic science has developed has an explanation for the multi-petaled blooms come to life. According to a genetic study done at the University of California, San Diego, a double flower is a result of three genes mutating within a flowering plant. When this mutation occurs, rather than produce the male and female sex organ layers of most flowers, the plant continuously produces asexual petals called sepals. The lack of sexual organs caused by the mutation answers the age-old question of why breeding double flowers is so difficult.
Double flowered blooms are prized for their healthy and full look, and can be found in many different varieties of flowers. Gardening catalogs, nurseries, and garden supply stores are all good places to look for double bloomed flowers for the garden. Some gardeners recommend avoiding planting double flowering plants in particularly cold regions, as it is believed this may impair the production of the double blooms.