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Beach Plum

 

Beach plum (Prunus maritima) is a plant aptly named. It is commonly found on ocean dunes and bay locations and only occasionally at river mouths and slightly upstream from New Brunswick south to Maryland.  It is deciduous and has a shiny medium green entire leaf with slight serrations on the margins. Beach plum can grow to a height of 8-10 feet (in protected locations such as farm fields and woods) but in the severe locations in which it most often found, where its height is governed by the wind, it is more common to find Beach Plum as a 2 to 4 foot specimen.

Beach Plum is found so frequently on the ocean dunes of the northeast that it is uncommon to find an established dune without its presence.  The association of dune and plum becomes so intimate, that the plant and dune together become a maritime land form, their fortunes both rise and fall together. The reasons for this association are the environmental factors of sand, salt and wind. Entire books are written on the subject of dune dynamics and plant response, however the central theme of plum and dune are basic. Beach Plum blocks sand laden wind and in so doing causes the wind to slow and deposit its load of sand around the plum on the dune. The branches of the plum create shelter around the plum which stops the sand around the plant from blowing away and deep plum roots hold the dune together and slow down erosion in times of exposure.

The study of Beach Plum as an agronomic fruit was quiet until efforts began in the early 20th century. The breeders took great interest in the fruits color variation (yellow, red, and shades of blue through purple) as well as the taste which ranges from sweet to head twisting sour. The goal of the breeders was to find the combination of  color and taste which would lead to commercial success.  According to a 1944 work by George Graves, the author of “The Beach Plum, It’s Written Record, the first plum marvel was a hybrid with a Japanese Plum called “Giant Maritima”. The plum was an 8 ¼” beast of a fruit but apparently the result was not commercially viable as it does not appear again in any record.

click photo to enlarge

click photo to enlarge

click photo to enlarge

As Beach Plum was dragged down the corridors of plant breeding, success evaded researchers, the essential combination of fruit quality, taste and production resisted their efforts. Research concentrated on sugar content revealing that the yellow fruits had the sweetest taste followed by the blues with dark purple becoming the most bitter. Breeding programs again declined until Cornell University recently started commercial study. Their program (www.beachplum.cornell.edu) focus on farm production of the fruit for sale as a fruit and as jelly.

In the past, Beach Plum had drawn more interest as a fruit than a naturalizing plant.  Plum was collected and eaten by native citizens for many centuries before John de Verrazano sent back reports of a blue plum on the beaches of the new world in 1524. Botanists gave the plum the name Prunus maritima, in 1787 and was soon after introduced into Europe as a new fruit. The next 60 years would find Beach Plum and its variations of form studied ad nauseum and fractured into several botanical categories.  The botanists Torrey and Grey grouped the plant back into Prunus maritima with two variations.

The influence of the plum on the dune increases the total mass of the sand on the dune which gives the plum more substrate to grow on. Plums grow into and above the increasing sand layers and the entire dune grows along with the plant community on it.  The plums screening affords better protection from salt and wind driven sand for the plant communities behind the dune which helps stabilize the dune in times of ocean storms as well.


A dune with a good stand of beach plum looks like many individual plants, in many cases what exists is actually two or three large specimens with only the top branches exposed. Plums will grow along with the dune, the plum tolerates sand coverage and when covered incrementally or completely, will sprout through the dune along many points from existing growth. What we do not see is the framework of branches beneath, a severe erosion event can expose the large tree-like super structure of the plum that is beneath the sand.

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