Raspberries

Raspberries have a unique biennial cane system that directly shapes their fertilization needs: perennial roots produce first-year vegetative canes (primocanes) that overwinter and fruit in their second year as floricanes, then die after harvest. This means the plant is simultaneously supporting fruit production on old canes while investing in vigorous new cane growth for next year's crop — a dual demand that makes nitrogen management the central challenge. The University of Maine Extension recommends 20 pounds of 10-10-10 per 1,000 square feet annually for established plantings, split between mid-spring and six weeks later. Excess nitrogen is a serious problem — it produces longer internodes, fewer fruiting laterals, increased disease susceptibility, and soft berries with poor shelf life. Fall-bearing (primocane-fruiting) varieties like Heritage require 1.5 to 2 times more nitrogen than summer-bearing types because they must complete vegetative growth and fruiting within a single season. The simplest diagnostic tool is measuring internode length on primocanes: an optimal 4-inch spacing indicates adequate nitrogen, while longer internodes signal excess. Boron is a critical micronutrient for raspberry production, essential for bud break and fruit set, yet better predicted through foliar tissue analysis than soil testing. Iron chlorosis — interveinal yellowing on young leaves — becomes problematic when soil pH rises above 7.0, making pH management essential in alkaline soils. Raspberries should never be planted where tomatoes, potatoes, or eggplant have grown recently due to shared susceptibility to Verticillium wilt.