Prune to rejuvenate overgrown raspberries in early to mid-spring just as their buds begin to swell (leaf out).
Remove all weak, broken, diseased, and insect-damaged canes.
Select five or six of the sturdiest raspberry canes. These will bear fruit this year. Cut all other canes down to the ground.
Shorten the remaining canes to chest height (4 to 5 feet from the ground).
Spread 1 to 2 inches of compost around the base of the raspberry plants or use a 10-10-10 commercial fertilizer applying according to package instructions.
Spread 2 to 3 inches of straw or other organic mulch around the raspberry plants.
Cut the canes that produced raspberries down to the ground. Do this as soon as you have harvested all the berries (summer or fall depending on variety). More canes should have emerged from the roots that did not bear fruit. Select the strongest five to seven canes and cut the rest to the ground. These will produce raspberries the following year.