White five-petaled flowers appear on raspberry canes in late spring, thereafter yielding tasty aggregate fruits that are red, black or purple. The most widely planted type is the red raspberry. Growing from perennial roots, new canes arise each year and mature. In their second year, these canes flower and yield their berry crop. The following winter the canes that had produced fruit die, but new year-old canes flower the next spring to keep a raspberry plant producing fruits year after year. Grow raspberries in U.S. Department of Agriculture plant hardiness zones 4 through 8a.
After years of selective breeding, horticulturists developed raspberries that produce one crop a year. The usual one-crop raspberry types are more commonly called summer raspberries. Summer raspberry canes grow all leaves in the first year, go dormant and yield flowers and fruits the next spring and summer, then die. Two-crop raspberries are called everbearing or fall-bearing. These types grow leaves on new canes in the first summer and then flower and bear some berries that first autumn. The canes go dormant over winter, then they bloom and flower again the next spring and summer and die by fall's end.
Across the temperate regions of the United States, regardless of latitude, plant raspberries in early spring when they're dormant. Keep the soil evenly moist and weed the bed to keep good air circulation around the plants. Fall-bearing raspberry plants may yield a flower or two the first fall, but don't expect much. The first growing season after planting the raspberry plants focus energy on developing a strong root system and the first robust new canes. These new canes will yield fruits next year.
First Fruit Production
Expect all raspberry plants to produce a notable flowering and fruiting the second year after planting in late spring or early summer. For example, if you plant the raspberry patch in March, you can expect a good fruit crop in June of the following year, and a heavier crop in subsequent years. Raspberry canes die after they produce summertime fruits. Promptly prune off dead canes in winter so both new canes rise and the year-old canes flower and fruit in their second year. Continually removing the oldest, just-fruited canes each winter keeps a plant developing new canes in perpetuity.
Healthy raspberry plants basking in lots of sunshine produce the most flowers. The ideal temperature for raspberry plants is between 65 and 70 degrees Fahrenheit around their leaves, with soil root temperatures no higher than 80 degrees. Excessive heat stresses plants and causes fewer or smaller flowers and fruits, according to the North Carolina Cooperative Extension Service. In addition, you should encourage bees to visit raspberries when in flower, as pollination results in fruits.