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Ostrya
knowltonii (Western Hop Hornbeam) Semi-desert.
Wet, shady, canyon bottoms. Spring. Ostrya knowltonii late fall yellow leaves stand out in the canyon bottoms that it favors. Male catkins form at branch tips in the summer and persist through the winter; female catkins will grow in the early spring about the time leaves begin growing. |
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Ostrya
knowltonii (Western Hop Hornbeam) Semi-desert.
Wet, shady, canyon bottoms of Southeast Utah and Northern Arizona. Spring. Western Hop Hornbeam is a rare tree in southeast Utah and is otherwise found only in northern Arizona and a few scattered areas of southern New Mexico and Texas. The tree is quite prominent on the Chesler Park Trail of Canyonlands National Park where hikers walk through the narrow Breezeway before descending into Elephant Wash. The tree is also even quite abundant in moist, rocky canyon bottoms near Moab, Utah. Ostrya knowltonii typically grows to a maximum of 10-30 feet tall and 6-15 inches in diameter often with several main trunks and often in close proximity to a number of other Ostrya knowltonii. The tree is prominent because of its cracked and shredded bark, hop-like seed pods, and male pollen-bearing catkins. (See the photographs below and for click more plant details.) "Ostrya" is Greek for "hardwood tree" and refers to the dense wood of the Hop Hornbeams (Western and Eastern) which gives them another common name, "Ironwood". Botanist Frank Knowlton (1860-1926) discovered the tree in 1889 below the rim of the Grand Canyon. (More biographical information about Knowlton.) |
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Ostrya
knowltonii (Western Hop Hornbeam) Semi-desert.
Wet, shady, canyon bottoms of Southeast Utah and Northern Arizona. Spring. In the picture at left, the maturing green seed pods on the female catkins (far left) resemble those of hops (various vine Humulus species). The male pollen-bearing catkin is in the center of the photo and is also shown in the next photographs. Since male and female flowers are separate but on each tree, the tree is termed "monoecious" (Greek for "one house"), in contrast to "dioecious" species which have male and female flowers on separate plants. |
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Ostrya
knowltonii (Western Hop Hornbeam) Semi-desert.
Wet, shady, canyon bottoms of Southeast Utah and Northern Arizona. Spring. These long, fresh, male pollen catkins have just opened and tiny stamens protrude.
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Ostrya
knowltonii (Western Hop Hornbeam) Semi-desert.
Wet, shady, canyon bottoms of Southeast Utah and Northern Arizona. Spring. Bark on younger trees is gray, with darker, slightly raised, longitudinal ridges. Mature bark is shredded, as shown in the photograph below of a five inch diameter trunk.
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Ostrya
knowltonii (Western Hop Hornbeam) Semi-desert.
Wet, shady, canyon bottoms of Southeast Utah and Northern Arizona. Spring. |
Range map © John Kartesz,
County Color Key
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Range map for Ostrya knowltonii |
Species present in state and native
Species present in state and exotic
Species not present in state
Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Eradicated
Questionable presence