Luther Burbank: Methods and Discoveries pp. 206-215 (1914)
THE ENNOBLEMENT OF THE BEACH PLUM
The Giant Maritima
|The Maritima, colloquially known as the Beach Plum, is an American wild species, growing abundantly along many of the the Eastern seaboards. The wild plum is very small and so acrid as to be almost inedible unless cooked. Mr. Burbank has greatly increased the size and quality of the fruit by selection, and he has also used it in highly interesting crossbreeding experiments.|
Perhaps the most astonishing result produced by hybridizing the little Beach plum is the fruit to which I have given the provisional name Giant Maritima.
This is a second-generation hybrid from an improved hardy Beach plum pollenized with one of the hybrid Japan plums.
In 1895, the first year this seedling bore, the fruit was one hundred times larger than its seed parent, the Maritima. In 1896, the fruit was even larger than in the previous year, and in 1899, as the tree gained in age and strength, the size was still further increased.
In that year some of the fruits were measured and found to be eight and a quarter inches in circumference.
The Beach plum from which this remarkable hybrid was developed is a native of the Atlantic coast of North America, growing on the sands and among rocks near the seashore from Labrador to North Carolina. It is known botanically as Prunus maritima.
It is one of the hardiest of all known wild plums, and habitually productive. It is a low, compact bush, rather than a tree, with rough, even thorny, branches, and small dull green oval leaves. The flowers are small, but are produced in great profusion, making it almost worthy as an ornamental plant. The fruits, as I have said, are small, usually less than half an inch in diameter; and they are bitter, being almost or wholly inedible unless cooked—yet making excellent preserves.
The Beach plum for many years has been known to possess some horticultural possibilities, especially hardiness, productiveness, and general "staying" qualities under the most trying conditions. The value of these characteristics was discovered soon after my general plum experiments were started, and every effort was made to cross it with some of the larger and finer species. For several years this cross could not be effected, mostly because the Beach plum blossoms very late, long after all other plums have shed their bloom.
Finally, however, very late blossoms of the latest plums of other species were cross-fertilized with some of the earliest Beach plum blossoms, the crosses being made both ways.
In the meantime I had been growing seedlings of the Beach plum by the hundred thousand. By continuous selection I had produced varieties bearing fruits nearly an inch in diameter, of a pleasing form and color, of delicious flavor. The trees, moreover, had almost incredible productiveness together with increased size and vigor.
Although my most enthusiastic friends often laughed at these extensive experiments with what they called my "huckleberry plum," and some of the best fruitgrowers made sport of the insignificant fruit, I saw in the little Beach plum great hardiness, late blooming, enormous productiveness, and the ability to withstand adverse conditions, and was sure of some measure of success.
Several crosses were finally made between the improved Maritima and the best cultivated varieties of other American plums. No really good fruits were obtained in the first generation, but some excellent varieties, both in productiveness and quality, were produced in the second, third, and fourth generations.
Some of the first-generation hybrid Maritimas make a much stronger growth than their wild parents, sometimes attaining four to six feet in two years, while the wild Beach plum on a good soil rarely grows more than three to three and one-half feet high in the same time.
The wild tree has short limbs, black bark, and small leaves. The first generation hybrids of these with the American and Japanese plums have longer, smoother, and larger leaves, lighter colored wood, and longer and more slender branches.
These hybrid seedlings are easily distinguished the first season, as the Beach plum has red roots, while those of the hybrid vary, most of them being lighter. Beach plum seedlings, no matter how young, from seeds crossed with other varieties, show various shades between the pale yellow or brown root of the European and Asiatic varieties and the red root of the wildling, and if there were no other test this would be amply sufficient to prove that the plants were hybrids.
Such, then, was the parentage of the Giant Maritima, which first bore fruit, as already noted, in 1905—fruit over two inches in length. When I first came across this enormous fruit on a tree with the Beach plum foliage and blooming habits, the branches literally hanging in ropes of gigantic fruits, I could hardly believe my own eyes.
The fruit begins to ripen here early in July, and when ripe it is a deep crimson, covered with a thin pale bloom. The flesh until fully ripe is very firm and solid, but it breaks down quickly when ripe. It is honey-yellow, with a pale greenish tinge. The quality is good. The fruit is fragrant, and as large as the Kelsey, Wickson, Climax, or any other plum known in 1905.
It is found necessary to thin the green fruit carefully, otherwise the tree would be crushed with its weight of fruit. It has been grafted into numerous older trees, and appears to be a strong grower. Having originated from such an unusually hardy wild stock on one side, it will no doubt produce a crop of fruit almost anywhere. In itself, however, this will never prove of much commercial value, as it lacks firmness of texture.
THE BEACH PLUM IN OTHER COMBINATIONS
The wild Beach plum was also crossed with my Combination plum, which has in its ancestry plums of almost every type. The resulting seedlings were not as good as had been anticipated, but two were very much liked by a well-known California fruitgrower, and were sold to him in 1908.
One of these was given the name "East." It is a prolific variety. The fruits are globular, pale yellow, half covered with a crimson bloom and numerous indistinct dots. The flesh, pearly yellow in color, is of good quality, though probably inferior to some of the best Japanese hybrid plums. The fruit ripens here from August first to fifteenth.
This was tried at San Jose for several years, but found to be too soft for shipping. It is, however, a desirable variety for home consumption. It has never been offered to the public.
The other plum from this cross is known as "Pride." It also proved to be of little value as a shipping plum. It ripens too quickly, so that it will not stand shipping any great distance.
Pride is apple-shaped, which is usually a desirable form. It is a good grower, an excellent bearer, and ripens about July 20th. The skin of the fruit is a deep red with a whitish bloom. The flesh is a dark red—showing a Satsuma cross—and of excellent quality.
Besides these, nearly two thousand other promising Maritima hybrids are now being grown from these crosses. Many of them are excellent in habit, productiveness, and hardiness. As yet they have not been sufficiently tested to warrant their introduction.
TRIBUTE FROM THE SAND CHERRY
Another native American plum which is as hardy as the Beach plum is Prunus besseyi commonly known as the Western Sand Cherry. Although it is called a cherry, it is really a plum and has been successfully crossed with the plums, as pointed out in an earlier chapter. It is thoroughly hardy in the central and northern states, and is found most often in Minnesota and the Dakotas.
My work with this variety has not been so extensive as with the Beach plum, but has resulted in the development of one new plum which has been thought worthy of introduction. It was offered in my catalog of 1911-12 under the name Epoch, and is described there as follows:
" 'Epoch' should be one of the hardiest of all known plums, as it is a cross of the western Sand Cherry and the American plum, both being about as near 'Arctic' plums as can be mentioned.
"The tree is a compact grower, dwarf, with dark brown wood, which always, without fail, produces ropes of fruit, each fruit one and a half inches in diameter, beautiful crimson, with shades and dots of yellow. Flesh pure deep yellow, firm, with a rich cranberry flavor, but sweeter, and when ripe very good. Ripens August 15th. The youngest, as well as the oldest, trees literally cover themselves with fruit, which keeps remarkably. Probably the most productive and best of all the 'Iron Clad,' extremely hardy dwarf plums."
As this variety has not been introduced long enough to get reports from growers in various parts of the country, it is not possible to say just how valuable it will prove to be. Its hardiness, however, is well established, for it has been grown in North Dakota, where the young trees have endured a temperature which no other plum had been able to live through.
This work of developing, hardy fruits for the colder sections is being pushed by other workers. Professor N. E. Hansen, for example, of the South Dakota Experiment Station, has been working for many years, especially in crossing the Sand Cherry with some of my best hybrid plums and with other varieties. He has been successful in producing several good varieties.
It is to be hoped that others will enter into this work, as hardy fruits are much needed in many northern regions of our country.
The American Horticultural Magazine, p. 79 (1943)
Meanwhile the idea of crossing the beach plum with other species was, and still is, the starting point in the minds of many interested in "improving" this native fruit. Luther Burbank was active at that time and claimed to have grown beach plum seedlings by the hundred thousand and to have selected forms with fruits nearly an inch in diameter, of pleasing form and color. His dream, so he wrote, was to make use of the great hardiness, late-blooming, enormous productiveness and ruggedness of Prunus maritima in his plant breeding program. No accurate record of Burbank's crosses seems to exist but apparently, starting in 1887 and continuing for 20 years or so, he mixed beach plums with hybrids of American and Japanese origin and came out with three named varieties and a host of untested seedlings.
Burbank's "Giant Maritima" was a second generation hybrid from an "improved" beach plum pollenized by one of the hybrid Japanese plums. At its fifth year of bearing, some of its deep crimson fruits were reported to have measured eight and a quarter inches in circumference but were of little commercial value, as they lacked firmness of texture.