Npn-plant

American mountain ash (Sorbus americana)

  • When to observe: Year-round
  • What to observe: Flowers, Fruits, and Leaves
  • Where to observe:
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American mountain ash is a USA-NPN regional plant species. Regional species are ecologically or economically important and are distributed more locally than calibration species. The NPN integrates these observations to better understand plant responses within the different geographic regions of the U.S. In addition, this species is an allergen. Observations on its phenology will provide valuable information to benefit people with allergies and the public health community.
American mountain ash is a deciduous shrub to small tree growing 10 to 40 feet tall. Its tiny, white flowers have both male and female parts, are grouped into showy, flat-topped clusters, and are insect-pollinated. American mountain ash prefers moist habitats, from the borders of swamps to rocky hillsides, and is common in openings or woods, scattered on uplands along edges of woods, and roadsides, and under semi-open stands. It is not very tolerant of drought, nor is it well adapted to warmer habitats; it is intolerant of shade.
You should observe...
Here are the phenophases you should observe about this plant.
Leaves 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.
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.
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.

Colored leaves

One or more leaves (including any that have recently fallen from the plant) have turned to their late-season colors.
Falling leaves

One or more leaves are falling or have recently fallen from the plant.
Flowers 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.
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.

Fruits Fruits

One or more fresh fruits are visible on the plant.
Ripe fruits

One or more ripe fruits are visible on the plant.

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.
If drought seems to be the cause of leaf color or fall for a plant, please make a comment to that effect.
Sorbus americana is favored by moose and white-tailed deer, which eat its foliage, twigs, and bark. Many other wildlife species, including birds and small mammals, eat its red berries. Humans cook the berries with meat and make them into jellies. The plant is also used medicinally. Although this is not a true ash, it has acquired its common name because its compound leaves are similar to those of true ashes (genus Fraxinus, family Oleaceae).

Gardens with this plant

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