Beach plum (Prunus maritima) is a deciduous shrub native to the Atlantic coastal plain from Maine to Maryland, where it forms dense thickets on dunes, bluffs, and sandy scrublands. Its small, tart fruit has supported a regional preserving tradition for generations, with commercial production concentrated on Cape Cod and Long Island.
The shrub tolerates salt spray, wind, and drought once established, making it one of the most practical native plants for exposed coastal sites. White flowers appear before leaf-out in early spring and require cross-pollination from a genetically distinct plant — at minimum two seedlings, or a named cultivar paired with another. Fruit ripen from late August into September, turning deep purple to nearly black. Preferred pH is 5.5–7.0; sandy or gravelly, free-draining soil is ideal. Heavy clay causes root problems. Named cultivars such as 'Autumn' and 'Flyer' produce larger, more uniform fruit than wild seedlings. Suckers spread freely and should be removed or managed if a tidy form is desired.
Beyond coastal dunes, beach plum functions as an informal hedge, bank stabilizer, or wildlife shrub. Birds and small mammals consume the ripe fruit heavily, and the thicket structure provides nesting cover. The fruit is used for jams, jellies, sauces, wine, and liqueurs.
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.
Black Knot
Hard, elongated galls form on stems and branches, starting olive-green and soft before turning black, corky, and woody. Galls girdle stems, killing all growth beyond the infection point. Severely infected plants develop multiple swollen knobs throughout the canopy.
Prune infected wood at least 8 inches below any visible gall during dormancy; sterilize pruning tools between each cut with 70% isopropyl alcohol or 10% bleach solution. Remove and destroy all pruned material — do not compost. In orchards or high-pressure sites, apply a copper-based or lime-sulfur fungicide at bud swell and again 10–14 days later. Remove nearby wild Prunus hosts, which serve as inoculum reservoirs.