The beach plum (Prunus maritima Marsh.) is a wild, native plum that grows in abundance along the beaches, among the sand dunes, and on the coastal plans from Virginia to Nova Scotia. It is very abundant on the New Jersey Shore, Cape Cod, and the islands of Martha's Vineyard and Nantucket. The fruit can be consumed fresh but is commonly used for the making of jam and jelly. Preliminary bathes of wine have also been encouraging. From bloom through fruit display, the plants can have high ornamental value also.
Growth and fruiting habits of the beach plum vary, however it tends to resemble a bush more often than a tree; it suckers freely from the roots and can produce dense thickets. The root systems are coarse, rangy and deep, especially on the sandy soils. The native home of the beach plum is in light, sandy soils or even the pure sand of sand dunes. Although it can exist under these conditions, it grows very slowly. When moved to better soils, it becomes much more vigorous and yields are typically improved.
The beach plum can be propagated from seed. Pits are cracked, and seed taken out and stored at 40°F in moist sand or sphagnum moss for two or three months. Without controlled stratification, it may take two years for the seed to germinate.
To propagate clones, asexual propagation by root cutting is the usual method. Pieces of root three to four inches long are buried two to three inches deep outside in a sandy soil in the fall. Pieces of root (diameter of a lead pencil) from plants no more than three years old give the best results. Cutting can be used but rooting percentage is typically low. Take terminal cuttings (4-6 inches) in late-July, and treat with 5000 ppm rooting hormone. They also can be grafted, however, plants on their own roots usually thrive much better than grafted beach plums.
Planting and Training
Beach plums, like cultivated plums, are best transplanted in spring. The size and shape of most beach plum bushes suggest a 10/15 x 10 foot spacing. They are prone to suckering and can form a hedgerow in not suckered.
Beach plums benefit from pruning
Late winter or early spring is the best time. The conventional type of pruning is as given to cultivated plums, first removing dead, diseased, weak wood, and crossing branches. Cut off low branches to keep the fruit off the ground. If the bush is still too thick, branches may be cut out of the top. Cutting them to the ground and allowing them to develop a new top can sometimes rehabilitate wild bushes in very poor condition best.
Beach plums need fertilizer but seldom respond to it in a wild state because of limiting water. In cultivation, four hundred pounds per acre of a 10- 10-10 or 500 pounds of an 8-8-8 are suggested or trial on bearing bushes in a moist soil. Young bushes should be fertilized lightly, and the amount doubled each year until the pound/plant rate is reached. The fertilizer should be broadcast, not concentrated about the trunk. Apply before bloom in the spring.
Cropping and Fruit
Most beach plums bloom heavily each year but set a crop only once every three or four year. Beach plums are self-sterile, and require cross-pollination. Rainy, foggy, dark, cold, and windy during bloom may considerably reduce or stop insect flight, therefore reducing pollination. Poor weather may also slow the growth of pollen tubes so that fertilization fails. It also may make conditions favorable for the development of the blossom blight form of the brown rot disease so that the blossoms are destroyed.
The fruit is small, similar in size and shape to a cherry, with a similar single pit. The color varies from red through blue to purple and almost black. Flavor varies from plum to grapey-plum. Skin ranges from thick and tannic to thin and inconspicuous. There is great variation in fruit rot susceptibility. Plants tend to biennial bear. Fresh eating quality ranges from bitter to very good and processing quality is excellent.
There are very few "commercial" varieties known. `Autumn' is a low spreading bush, which produces annual crops. The fruit has good size and quality. Three others, `Stearns', `Northneck' and `Squibnocket' are also named varieties. `Stearns' has fine ornamental qualities, and its fruit processes well. `Northneck' and `Squibnocket' are valuable as ornamentals and soil binders. Plants of named varieties are difficult to find and some nurseries carry only "unnamed" seedlings. The NJAES Fruit Breeding Program has a few advanced selections with superior fruit characteristics and disease resistance.
The beach plum is attacked by several insects, which, if not controlled, may seriously reduce the crop. By far the most important insect pest is the plum gouger, which, some years, destroys over half the crop. The gouger is a reddish-brown snout beetle. Eggs are laid in the newly set fruit and the larvae develop in the pit, reaching maturity and emerging at about the time the fruit ripens in late August, and September. Infested fruit does not size or ripen normally, but remains small and green.
The plum curculio commonly infests beach plums. This is also a reddish-brown snout beetle but is distinguished from the plum gouger by its smaller size, rough exterior and the presence of white and black mottling on the back. The egg puncture of the plum curculio is distinctive, being a crescent shaped scar. Infested fruit drop prematurely.
European red mite is also causing a typical bronzing of the foliage. The fruit on infested bushes remains small, poorly colored, and in severe infestation the fruit and foliage may drop prematurely. Other insects of minor importance to beach plums are the eastern tent caterpillar, fall webworm, a leaf pouch gall mite, European fruit lecanium, Oriental fruit moth, and apple leaf skeletonizer.
Plum pockets or plum bladders can be serious pest of beach plums. The fungus winters over in infected twigs; it attacks both leaves and fruit. Infected leaves become twisted and yellowish. Infected fruit becomes swollen, misshapen, hollow, and then drop to the ground. Spraying during early spring while the bushes are still dormant keeps this disease under control.
Brown rot, a very common and destructive fungus disease of peaches, cherries, and plums, is one of the most troublesome of beach plums. It may infect: the blossoms (called "blossom blight") and prevent the set of fruit; the twigs (called "twig blight"); large limbs, causing cankers; or green or ripe fruit, especially where it has been injured by insects, causing it to rot. These decayed fruits dry, shrivel, and become mummies. The disease 3 lives over winter in these mummies and in limb cankers. Fruiting bodies, which liberate spores for re-infection, can be formed on both. Brown rot can be controlled by thorough and repeated fungicide sprays.
Lead spot, or shot hole is quite common on beach plums. It is a fungus disease that causes round irregular reddish or purplish spots that may turn brown and drop out. Damaged leaves often turn yellow and drop. This also can be controlled by fungicide sprays.
Control of beach plum pests is obtained by following a peach schedule.
Baily. J.S and W.E. Tomlinson. The Beach Plum in Massachusetts. Extension Publication No. 315. U. of Mass. Coop. Ext. Ser.
Reich, L. 1991. Uncommon Fruits Worth of Attention. Addison-Wesley. Reading, MA.