7th Annual Meeting, Agricultural Science p. 51-56 (1886)
Hybridity and its Effects
T. V. Munson
IV. Genus Hybrids. Hybrids between Plum and Peach.
Among the wild native plums, hybrids are about as common as between the species of wild grapes, and as with them and the oaks and catalpas, hybridization seems to conduce to vigor, fruitfulness and longevity in the mixtures generally. But when we come to mingle plum and peach, we observe a very different result.
In my orchard a Wild-Goose plum tree stood near Alexander peach trees. They bloomed together. I saved seeds from the plum tree, selecting remarkably large, fine specimens (I do not say the pollenization by the peach made them larger than pure Wild-Goose would have been, but it seemed a little suspicious), and grew trees from them. Imagine my astonishment in finding nearly half of all that grew, much resembling peach trees, and not recognizable as offspring of Prunus Chicasaw, the species to which Wild-Goose belongs. These were at first the most vigorous by far, but the second year, in the rainy months of May and June, they mildewed in leaf and became puny, and now, the third year, they are nearly all dead or dying. They set small flower buds but cast them seemingly without a cause, without blooming. The pure plum seedlings, from same lot of seed, are more or less vigorous; some having much the appearance of the parent, others with small glossy leaves, like the common Chicasaws, probably crosses with such growing near; and some with markings of P. Americana; probably hybrids with Weaver growing near. Altogether, a more variable lot of plum trees could scarcely be collected. Nothing could more clearly demonstrate the results of intermingling blood nearly allied and at a distance. The plum crosses and hybrids among them have begun bearing nicely. The Alexander peach may be a poor variety to use as a parent as I am quite sure, but aided by other examples to be related, I conclude that the peach and plum are never likely to produce much more than worthless mules.
The Blackman plum, produced accidentally from seed of Wild-Goose, is unquestionably a hybrid with the peach. It is vigorous, but a very shy bearer, generally casting its bloom-buds, just as they are about to open. The generative organs are very small, the petals wanting, the stamens small and exserted from the throat of the calyx. A casual observer would scarcely think the tree had any bloom. Occasionally it produces a fine fruit. I do not know whether the seed is capable of germination or not.
A few years ago I gathered seed of P. umbellata (or a subspecies of it which grows abundantly here), which grew on trees standing near an old seedling peach orchard. Among the seedlings grown from these (for stocks, on account of being sproutless) probably 10,000 stocks, were three, which by their much greater growth and general peach-like aspect, and in the prussic acid taste in the bark and leaves, attracted my attention. I planted them in orchard to fruit if possible. They grew and are now five years old, have set small bloom-buds in pairs like peaches, not in clusters like the Umbellata plum, but invariably they fail to bloom, and are cast off without an apparent cause, when everything else among stone fruits is in full bloom.