Blenheim is an heirloom apricot variety originating in England and introduced to California in the 19th century, where it defined commercial apricot culture in the Santa Clara Valley for over a century. The fruit is medium to large, deep golden-orange with sweet-tart, aromatic flesh widely regarded as superior for fresh eating, sun-drying, and preserves. As commercial orchards gave way to development, home-grown Blenheim trees became increasingly important for growers who want access to the variety.
Blenheim requires approximately 400–500 chill hours and opens flowers early in the season, sometimes before the average last frost. Planting on a slope or elevated ground where cold air drains away protects the crop in marginal years. The tree is self-fertile and heavy-bearing when the crop is not cut by frost. Train to an open vase shape and prune annually in late winter to remove dead, crossing, and inward-growing wood; improved airflow reduces fungal disease pressure significantly. Thin fruitlets to 3–4 inches apart after natural fruit drop to improve size and prevent limb breakage. Fruit transitions from nearly ripe to overripe quickly — check daily as harvest approaches. Mulch over the root zone to conserve moisture and moderate soil temperature. Trees tolerate mildly alkaline soils but perform best in the slightly acidic to neutral range.
Fresh apricots are a concentrated source of beta-carotene and potassium. Dried fruit has served as a shelf-stable food staple in Mediterranean and Central Asian food traditions for centuries. In Traditional Chinese Medicine, bitter apricot kernels (xing ren) are prescribed for dry cough and constipation; apricot kernel oil is extracted for use in cosmetic and topical skin preparations.
Brown Rot
Blossoms turn brown and cling to the twig rather than dropping (blossom blight). Developing or ripe fruit shows soft, rapidly expanding brown lesions covered in distinctive ash-gray powdery spore tufts. Infected fruit shrivels into hard mummies that persist on branches through winter.
Remove and destroy mummified fruit from branches and the ground at pruning time. Apply sulfur or a registered fungicide at full bloom and again 2–3 weeks before harvest during wet seasons. Thin fruit to reduce canopy density and direct fruit-to-fruit contact, which speeds spread.
Bacterial Spot
Small water-soaked angular lesions on leaves that turn dark brown and drop out, leaving ragged shot-holes. Sunken, water-soaked dark spots on fruit skin that can crack and invite secondary rots. Twig cankers with gummy amber exudate on young wood.
Apply copper-based bactericide beginning at petal fall and repeat on a 10–14 day schedule through early summer. Avoid overhead irrigation. Prune for open canopy airflow. Remove and destroy infected shoots during dormant pruning. Elberta has moderate susceptibility; consider planting resistant cultivars in high-pressure sites.
Powdery mildew
White or grey powdery coating on leaves — usually starting on older growth in humid conditions or when nights cool.
Improve air circulation by thinning plants. Apply neem oil or potassium bicarbonate spray at first sign. Avoid overhead watering.
Shot Hole Disease
Small reddish-purple spots on leaves that dry out and drop, leaving ragged holes across the leaf surface. Severe infections cause early defoliation. Dark sunken lesions may appear on young stems.
Remove and dispose of infected leaves and stems. Avoid overhead irrigation and wetting foliage. Apply a copper-based fungicide in fall just before seasonal rains begin; repeat in early spring if the previous season was severe. Ensure good air circulation through selective pruning.
Cytospora Canker
White or blue-white pitch masses ooze from bark on lower branches and the trunk. Affected branches die back progressively from the tip inward; bark beneath the resin is discolored brown and may have a resinous, sunken appearance.
Prune infected branches well below the canker margin into healthy wood and destroy all cuttings. Sterilize pruning tools with 70% isopropyl alcohol between each cut. No effective fungicide is available; prevent recurrence by avoiding drought stress, soil compaction, and mechanical bark injury.
Armillaria Root Rot
Thinning, yellowing canopy with progressive dieback; white, fan-shaped mycelial mats visible beneath bark at or just below the soil line; honey-colored mushroom clusters appearing at the trunk base or on surface roots in autumn.
No chemical cure exists. Improve drainage and avoid any injury to roots or trunk. Remove severely infected trees along with as much root material as possible. Do not replant susceptible species in the same spot.
Eutypa Dieback
Shoots arising from infected scaffold limbs are stunted and produce small, cupped, chlorotic leaves; heavily infected spurs may fail to break dormancy. Cross-section of affected wood reveals a wedge-shaped zone of dead, discolored tissue. Gum may ooze from the bark surface above the canker margin.
Prune out all affected wood at least 6 inches below the edge of visible discoloration. Sterilize cutting tools between each cut with 70% isopropyl alcohol. Avoid large-diameter pruning cuts during wet weather, as Eutypa lata spores are released and germinate during rain events. Apply a registered wound protectant to all cut surfaces larger than 1 inch in diameter.