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American plum is a native, deciduous, sometimes thicket-forming, erect shrub or small tree. The growth habit of this species can vary considerably; plants range from shrubs approximately 3 feet (1 m) in height to arborescent individuals growing up to 32.8 feet (10 m). On the Great Plains this species typically grows from 9.8 to 26.2 feet (3 to 8 m) tall and is rarely treelike. In Utah, American plum forms thickets reaching heights of up to 16.4 feet (5 m), and treelike individuals are uncommon.
The leaves are somewhat stout with pubescent, usually glandless petioles; twigs often become somewhat spinelike at the tips. White flowers usually appear before the leaves and are borne in fasicles of two to five on the tip of spur branchlets or from axillary buds formed the previous season. Fruits are yellow to red plums (drupes), at least 0.8 inch (2 cm) long with yellow flesh and a compressed stone. Although this species sometimes produces small, hard plums, the fruits are generally fleshy and highly palatable. Occassionally trees cultivated for plums escape and persist. Horticultural varieties can be distinguished from the native species by their larger petals, smaller flower clusters (one to three per node), and sometimes by the gland-tipped teeth of the leaves. [4]
| American plum typically blooms from April to May in the Pacific Northwest and on the Great Plains. Flowers characteristically appear before the leaves and are borne in fasicles of two to five on the tip of spur branchlets or from axillary buds formed the previous season.
FIRE ECOLOGY OR ADAPTATIONS: Presumably this native plum is somewhat resistant to fire due to its tendency to spread through underground stems [34]. To a lesser degree, postburn regeneration probably also involves the germination of off-site seed dispersed by mammals. Two other Prunus species indigenous to the western United States, chokecherry (Prunus virginiana) and bittercherry (Prunus emarginata), are well adapted to disturbance by fire. [4] |
The fruit of American plum is a yellow to red drupe containing a
compressed stone. Seeds are approximately 0.6 to 0.7 inch (1.5 to
1.8 cm) long and 0.4 to 0.5 inch (1 to 1.2 cm) wide. As with all
species within the Prunus genus, seed dormancy is a problem. In
order to overcome dormancy, seeds must be exposed to an
afterripening period in the presence of oxygen and moisture.
germination is usually enhanced following cool, moist stratification
for 90 to 150 days at 50 degrees F (10 degrees C); germinative
capacity is approximately 60 percent following stratification at 50
degrees F (10 degrees C) for 60 days. Germination requirements
appear to vary geographically.
American plum seed from
northern Minnesota germinated much better at 50 degrees F (10
degrees C) than at higher temperatures; whereas optimal germinating
temperatures for seeds from Nebraska are from 70 to 80 degrees F
(21.1 to 26.6 degrees C). Seedbed characteristics are virtually
unstudied in this species. Although the majority of seeds are
presumed to be deposited beneath the parent plant, frugivorous
mammals probably function as long-distance dispersal vectors. Rogers
and Applegate speculated that black bears are one of only a few
disperal agents for large-seeded species such as American plum.
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