Raspberries are grown for the fresh fruit market and for commercial processing into individually quick frozen (IQF) fruit, purée, juice, or as dried fruit used in a variety of grocery products. Traditionally, raspberries were a mid-summer crop, but with new technology, cultivars, and transportation, they can now be obtained year-round. Raspberries need ample sun and water for optimal development.
While moisture is essential, wet and heavy soils or excess irrigation can bring on Phytophthora root rot which is one of the most serious pest problems facing red raspberry. As a cultivated plant in moist temperate regions, it is easy to grow and has a tendency to spread unless pruned. Escaped raspberries frequently appear as garden weeds, spread by seeds found in bird droppings.
Two types of most commercially grown kinds of raspberry are available, the summer-bearing wild type that produces an abundance of fruit on second-year canes (floricanes) within a relatively short period in mid-summer, and double- or “ever”-bearing plants, which also bear some fruit on first-year canes (primocanes) in the late summer and fall, as well as the summer crop on second-year canes.
Raspberries are traditionally planted in the winter as dormant canes, although planting of tender, plug plants produced by tissue culture has become much more common. A specialized production system called “long cane production” involves growing canes for 1 year in a northern climate such as Scotland (UK) or Washington State (US) where the chilling requirement for proper budbreak is met early.
These canes are then dug, roots and all, to be replanted in warmer climates such as Spain where they quickly flower and produce a very early season crop. Plants should be spaced 1 m apart in fertile, well-drained soil; raspberries are usually planted in raised beds/ridges if there is any question about root rot problems.
Raspberries are very vigorous and can be locally invasive. They propagate using basal shoots (also known as suckers); extended underground shoots that develop roots and individual plants. They can sucker new canes some distance from the main plant. For this reason, raspberries spread well and can take over gardens if left unchecked.
The fruit is harvested when it comes off the torus/receptacle easily and has turned a deep color (red, black, purple, or golden yellow, depending on the species and cultivar). This is when the fruits are most ripe and sweetest. Excess fruit can be made into raspberry jam or frozen