American plum is native to the eastern United States. The tree produces edible fruits, and is host to the hop aphid, which is damaging to cultivated hops. Hops and American plums should not be cultivated in the same vicinity.
American plum is a deciduous, large shrub or small tree growing 3 to 33 feet tall that can form thickets. Its showy, white flowers have both male and female parts, are grouped in small clusters along the branches, and are insect-pollinated.
American plum grows on moist to dry sites ranging from the plains to lower elevations in the mountains; and on sites with sandy to rich loam soils in prairies, woodlands, and pastures, and along roadsides, river banks, and ravines. It is somewhat tolerant of saline soils.
American plum is an allergen species. Observations on its phenology will provide valuable information to benefit people with allergies and the public health community.
In addition, American plum has been selected for monitoring by our partner, Monarch Watch, because it is an important nectar plant for monarch butterflies. If you are a member of Monarch Watch, please see the monitoring instructions on the Monitoring Partners page.
Monarch Watch observers should look at the "open flowers" phenophase.
If drought seems to be the cause of leaf color or fall for a plant, please make a comment to that effect.
Do you see...?
Breaking leaf buds One or more breaking leaf buds are visible on the plant. A leaf bud is considered "breaking" once a green leaf tip is visible at the end of the bud, but before the first leaf from the bud has unfolded to expose the leaf stalk (petiole) or leaf base.
How many buds are breaking?
Less than 3
3 to 10
More than 10
Leaves One or more live unfolded leaves are visible on the plant. A leaf is considered "unfolded" once the leaf stalk (petiole) or leaf base is visible. New small leaves may need to be bent backwards to see whether the leaf stalk or leaf base is visible. Do not include dried or dead leaves.
What proportion of the canopy is full with leaves?
Less than 5%
5-24%
25-49%
50-74%
75-94%
95% or more
Increasing leaf size A majority of leaves on the plant have not yet reached their full size and are still growing larger. Do not include new leaves that continue to emerge at the ends of elongating stems throughout the growing season.
What proportion of full size are most leaves?
Less than 25%
Colored leaves One or more leaves (including any that have recently fallen from the plant) have turned to their late-season colors.
What proportion of the canopy is still full with green leaves?
Falling leaves One or more leaves are falling or have recently fallen from the plant. More...
Flowers One or more fresh flowers or flower heads (inflorescences) are visible on the plant. Flower heads include many small flowers that usually do not open all at once. Do not include wilted or dried flowers that remain on the plant, or heads whose flowers have all wilted or dried.
How many fresh flowers or flower heads are present?
Open flowers One or more open fresh flowers are visible on the plant. Flowers are considered "open" when the reproductive parts (male stamens or female pistils) are visible between unfolded or open flower parts. Do not include wilted or dried flowers that remain on the plant.
How many fresh flowers are open?
Peak flower: The plant has a large number of flowers and one half (50%) or more are open and still fresh.
Fruits One or more fresh fruits are visible on the plant.
How many fresh fruits are present?
Ripe fruits One or more ripe fruits are visible on the plant.
How many fruits are ripe?
Recent fruit drop One or more fresh mature fruits or seeds have dropped or been removed from the plant since your last visit. Do not include obviously immature fruits that have dropped before ripening, such as in a heavy rain or wind.
How many mature fruits have dropped?
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