Chester is a thornless, semi-erect blackberry prized for heavy yields of large, sweet-tart berries that ripen in mid to late summer, later than most, and for its cold hardiness; it is reliable in zone 5 where many thornless types winter-kill. The canes are vigorous and need a trellis to keep the fruit off the ground, and thornless canes make picking and pruning far more pleasant.
Plant bare-root or potted plants in early spring, 5 to 6 feet apart with 8 to 10 feet between rows, in fertile, slightly acid soil in full sun, and give them 1 to 2 inches of water a week while the fruit sets and ripens. Fruit is borne on second-year canes, so the annual rhythm matters: cut out the spent fruiting canes right after harvest, tie in the new ones, and thin to four to six strong canes per plant. Tip the new canes at 4 feet in summer to make them branch.
Pick when the berries turn from glossy to dull black and pull free with a light touch; a shiny berry is still sour. Birds take their share, and a net over the row at ripening is the only answer. It is disease resistant and rarely troubled by the cane blights that hit older varieties. Bees work the white spring flowers.
Cane Anthracnose
Small purple spots on young canes that enlarge into gray, sunken lesions with purple borders. Severe infections weaken canes and reduce fruit quality.
Prune and destroy infected canes. Improve air circulation by thinning. Apply lime sulfur during dormancy before bud break. Avoid overhead watering.
Botrytis (grey mould)
Grey fuzzy mould on petals and stems, worst in cool wet conditions.
Remove affected parts immediately. Improve air circulation. Avoid overhead watering. Apply copper fungicide if severe.
Crown Rot
Lower leaves yellow and wilt; the base of the rosette turns brown and soft, sometimes with white fungal threads at the soil line. Plants collapse in wet conditions.
Remove and destroy affected plants. Improve drainage and avoid overhead watering. Do not mulch directly against the crown. Space plants for airflow and avoid replanting in the same wet spot.
Japanese Beetle
Popillia japonica →Adults skeletonize leaves and devour petals and buds; aggregations escalate rapidly. Grubs destroy turf in late summer and fall.
Hand-pick adults in early morning into soapy water - beetles are sluggish when cool. Neem oil applied to foliage deters feeding but must be reapplied after rain. For grubs, apply milky spore (Bacillus popilliae) to turf - it takes 1–3 seasons to establish but provides long-term biological control. Beneficial nematodes (Heterorhabditis bacteriophora) applied in late August when grubs are young and near the surface offer faster results. Never use pheromone traps.
Spotted Wing Drosophila
Drosophila suzukii →Soft, collapsing berries with small puncture marks; white larvae inside ripening or ripe fruit.
Harvest fruit promptly and frequently. Remove and dispose of overripe or fallen berries. Use fine-mesh netting or traps. Refrigerate harvested fruit immediately.