size, and taste. Description and growth Strawberries are often grouped according to their flowering habit. Traditionally, this has consisted of a division between "June-bearing" strawberries, which bear their fruit in the early summer and "ever-bearing" strawberries, which often bear several crops of fruit throughout the season. One plant throughout a season may produce 50 to 60 times or roughly once every three days. Research published in 2001 showed that strawberries actually occur in three basic flowering habits: short-day, long-day, and day-neutral. These refer to the day-length sensitivity of the plant and the type of photoperiod that induces flower formation. Day-neutral cultivars produce flowers regardless of the photoperiod. Cultivation Strawberry cultivars vary widely in size, color, flavor, shape, degree of fertility, season of ripening, liability to disease and constitution of plant. On average, a strawberry has about 200 seeds on its external membrane. Some vary in foliage, and some vary materially in the relative development of their sexual organs. In most cases, the flowers appear hermaphroditic in structure, but function as either male or female. For purposes of commercial production, plants are propagated from runners and, in general, distributed as either bare root plants or plugs. Cultivation follows one of two general models—annual plasticulture, or a perennial system of matted rows or mounds. Greenhouses produce a small amount of strawberries during the off season. The bulk of modern commercial production uses the plasticulture system. In this method, raised beds are formed each year, fumigated, and covered with plastic to prevent weed growth and erosion. Plants, usually obtained from northern nurseries, are planted through holes punched in this covering, and irrigation tubing is run underneath. Runners are removed from the plants as they appear, to encourage the plants to put most of their energy into fruit development. After harvesting, the plastic is removed and the plants are plowed into the ground. Strawberry plants produce more and better fruit when they are young. After a year or two, they decline. Replacing them annually improves yields and enables denser planting. However, this necessitates a longer growing season, for the plants to establish themselves. It also costs more to annually purchase plants, form new mounds, and cover them with (new) plastic. The other major method retains plants for multiple years. This is most common in colder climates. The plants are grown in rows or on mounds. This method requires lower investment and lower maintenance, overall.