According to observations of naturalists and beekeepers.
Where are you?
30 kilograms per ha
SOURCE FOR HONEY BEES:
Major in some areas
American red raspberry occurs throughout most of the temperate regions of the world. In North America it grows from Alaska through Canada to Newfoundland, southward to North Carolina and Tennessee in the East, and to Arizona, California, and northern Mexico in the West. The native American red raspberry is Rubus idaeus subsp. strigosus.
R. i. subsp. idaeus grows across northern Europe to northwestern Asia. It is cultivated in Hawaii and throughout much of North America and has naturalized in many locations.
American red raspberry is a deciduous, erect or arching, thicket-forming shrub which grows from 1.6 to 9.8 feet (0.5-3 m) in height. The total height and extent of growth is largely attributable to climatic factors. Woody stems are bristly or prickly with shreddy, exfoliating yellow-brown bark. Leaves are alternate and pinnately compound in leaflets of three to five. Leaves are green and glabrous to hairy above but white or gray, hairy to glabrate and greenish beneath. Small showy perfect white flowers are borne in clusters of one to four in a compound cyme. Fruit of the American red raspberry is made up of many to several, red or pinkish-purple drupelets. Aggregates of drupelets are commonly referred to as a "berry."
American red raspberry is typically biennial, with each shoot passing through well-defined phenological stages during its 2-year lifespan.
Flowerbud initiation is influenced by temperature, genetics (cultivar), and geographic location. Flowering is also related to the age and vigor of the plant and the date at which vegetative growth terminates. Flowerbud initiation is triggered by low temperatures and short days and generally begins in late summer or autumn. Flowerbud initiation can be induced by exposure to temperatures of 55 degrees F (12.8 degrees C) at 9 hour days or 50 degrees F (10.0 degrees C) at 16 hour days. Although flower bud initiation occurs overwinter in most red raspberries, initiation in primocane-fruiting cultivars begins in summer. Bud break typically occurs in early spring. Evidence suggests that higher spring temperatures may promote earlier and more rapid flowering.
Fruit maturation begins soon after flowering. Timing of flower bud initiation largely determines fruiting season, although fruiting dates also vary according to cultivar and geographic location.