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Populus tremuloides Observations
(quaking aspen)
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Introduction to the NPN Native Species Observation Program
Quaking aspen (also known as aspen popular, trembling aspen, golden aspen, mountain aspen, popple, poplar, and trembling poplar) is common in both dry and moist woods, but cannot tolerate shade. It is a deciduous tree, growing up to 30 m tall, with a smooth trunk and light green or pale bark. Large trees can have black cracks in the bark at the base. Poplar trees are either male or female - only male trees are observed for NPN. Leaves are small (3-7 cm long), light to medium green in color, and round-shaped with a small, sharp tip. Flowers are found in catkins, which look like soft caterpillars hanging from twigs; blooming is completed before leaves emerge. Male flowers: Fuzzy catkins emerge in late winter, and lengthen in early spring to reveal red/pink pollen sacs. These release pollen into the air, and the catkin eventually dries up and falls off. Female flowers: Catkins turn green and capsules form, to later release fluffy, white seeds.
Source: Plantwatch Canada
You should record when five well-defined phenological events occur for quaking aspen:
- Beginning of flowering, first flowers open (BF) is the date when in at least three places on the plant the first flowers have opened completely (Photo by Elisabeth Beaubien).
- Sprouting of leaves (SL) is the date when the buds begin to burst open in at least three places on the plant under observation. The first green is visible on the young spring shoots and the first scales may fall off the buds.
- Beginning of the unfolding of leaves, first leaf surfaces visible (UL) is the date when in at least three places on the plant under observation first leaves have pushed themselves completely out of the bud or leaf sheath. The leaves have unfolded completely, so that the leaf stalk or leaf base is visible (sometimes only recognizable by bending back the young leaf). At this point, the individual leaf has taken its ultimate form, but has not yet reached its final size.
- Fruit ripe (FR) is the date when in at least three places on the plant under observation, the fruit shows the coloring characteristics of the plant variety (i.e., is ripe), and can be easily removed (i.e., is ready to fall from the plant).
- Coloring of leaves (CL) is the date when approximately 50% of the leaves (including those that have fallen to the ground) have taken on the colors of autumn.
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Please record average dates for each event among multiple plants of the same species. Report by email if any plant appears in poor health or event dates for same-species plants vary by more than a few days.
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