Ament, Catkin

ament [ AM–uhnt, EY-muhnt ] noun: a catkin

catkin [ KAT-kin ] noun: a raceme or spicate inflorescence, as of the Betulaceae (birches), Quercus (oak), or Salicaceae (willows); also called an ament. adjective catkinate: bearing scaly bracts and unisexual, usually apetalous flowers

During the fall, immature male flowers of Corylus avellana ‘Contorta’ appear on catkins, persisting through winter and blooming early spring. — *Corylus avellana* ‘Contorta’ (corkscrew hazel): Immature male flowers (4 stamens with 2 bractlets) develop three per bract on racemose catkins in fall, persist through winter, and bloom early spring.
Photo © Mary Free

Catkins/aments are inflorescences in the form of racemes or spikes. Some have described them as furry clusters or cylindrical structures of tiny leaves and apetalous flowers on a central stalk. The word catkin may come from the old Dutch katteken for kitten. Some catkins are described as resembling cats’ tails; others say hairy caterpillars. The word ament comes from the Latin amentum: “strap.”

Catkins can be male or female but each one is unisexual. Some catkin-bearing plants are monoecious, meaning they bear both male (staminate) and female (pistillate) flowers on the same plant, though as separate structures. Dioecious plants bear male and female flowers on separate plants. Many plants that reproduce through catkins are trees and are pollinated by wind. Because they do not depend on attracting insects or other creatures to carry pollen to fertilize them, the flowers can afford to be small and inconspicuous.

In some species the male catkins are pendulous and the females erect; in others the reverse is true. Male catkins are generally larger and more prominent, producing copious amounts of pollen, as wind pollination tends to be wasteful; there is no guarantee the wind will blow the pollen to the ovary of a female of the same species at the right time for it to develop into a fruit or seed.

Monoecious Betulaceae (Birch Family)

Alnus serrulata (smooth alder) erect female catkins have a few flowers— red/purple ovaries with a pair of styles—grouped behind each floral scale. — *Alnus serrulata* (smooth alder): A few flowers—naked ovaries with a pair of styles—grouped behind each floral scale comprise the ¼” long, erect, red or purple female catkins. Photo © Mary Free

Betula lenta (cherry birch, black birch) male and female catkins in Wallingford, CT. Photo © Doug McGrady CC BY 2.0 — *Betula lenta* (sweet or black or cherry birch): Pendulous male and erect female catkins consist of numerous florets and their bracts. Photo © Doug McGrady CC BY 2.0 [Image cropped]

The erect pistillate catkins of Betula nigra (river birch) have 1–3 flowers per bract. Male catkins are pendulous. — *Betula nigra* (river birch): Pendulous male catkins have yellow flowers somewhat obscured by small bracts; erect female catkins have 1–3 flowers per bract. Photo © Mary Free

Carpinus caroliniana (American hornbeam) catkins at Longwood Gardens. Photo © Tom Potterfield CC BY-NC-SA 2.0 [Image cropped] — *Carpinus caroliniana* (American hornbeam): Reddish green bracts partially hide male flowers on drooping, sessile catkins. Photo © Tom Potterfield CC BY-NC-SA 2.0 [Image cropped]

Ostrya virginiana (hop hornbeam) catkins in April at the Meadow Garden, Longwood Gardens. Photo Tom Potterfield ©CC BY-NC-SA 2.0 — *Ostrya virginiana* (hop hornbeam): 1-2” long, drooping male catkins are often arranged in groups of three. Photo © Tom Potterfield CC BY-NC-SA 2.0 [Image cropped]

**Monoecious Quercus (Oak) and Juglandaceae (Hickory/Walnut Family)**

Quercus alba (white oak): 2-3½” long, greenish-yellow male catkins develop at new growth's base (flowers have calyxes & several stamens). — *Quercus alba* (white oak): 2-3½” long, greenish-yellow male catkins develop at new growth’s base (flowers have calyxes & several stamens). Photo © Mary Free

Quercus rubra (northern red oak): 2-4” long, yellowish-green male catkins about; these catkins often occur in are produced from the axils of last year's leaves toward the tips of twigs. Flowers are less than 1/8" across, consisting of several stamens and a calyx partially hidden by hairy bracts. — *Quercus rubra* (northern red oak): 2-4” long, yellowish-green male catkins are produced from axils of last season’s leaves toward twig tips. Photo © Elaine Mills

Quercus phellos 2–3-inch long, drooping, yellowish male catkins with flowers consisting of a cup-shaped calyx and several stamens. — *Quercus phellos* (willow oak): 2–3″ long, drooping, yellow-brown male catkins have flowers with a cup-shaped calyx and several stamens. Photo © Mary Free

Carya tomentosa (mockernut hickory) displays drooping yellow-green male catkins up to 6” long in April. — *Carya tomentosa* (mockernut hickory): ~6” long, drooping yellow-green male catkins display hirsute bracts and anthers. Photo © Elaine Mills

Male catkins of Juglans nigra — *Juglans nigra* (black walnut): Male catkins have 17-50 stamens per flower. Photo © Famartin CC BY-SA 4.0

Dioecious Salicaceae (Willow Family)

Populus male catkin. Photo © Famartin CC BY-SA 4.0 — *Populus* sp.: Pendulous, sessile male catkins flower before leaves emerge. Photo © Famartin CC BY-SA 4.0

Salix caprea (goat or pussy willow): Male florets—a pair of yellow-anthered stamens—emerge from an erect, silky, bud-shaped catkin. Photo © Julianne Free — *Salix caprea* (goat or pussy willow): Male florets—2 yellow-anthered stamens, black bract at base—arise from erect, silky, bud-like catkins. Photo © Julianne Free

Salix caprea (goat willow) female catkin. — *Salix caprea* (goat or pussy willow): The silky, pear-shaped ovaries of semi-erect female catkins have a beak that gradually tapers to a style. Photo © Lou Free

Salix nigra (black willow) male catkins. Photo courtesy of Brenda Loveless, USFWS — *Salix nigra* (black willow): Ascending, widely spreading, or pendulous male catkins have flowers with 4–6 stamens and anthers with strongly recurved axes. Photo courtesy of Brenda Loveless, USFWS

References

Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico [Online]. 25+ vols. New York and Oxford. http://beta.floranorthamerica.org. Accessed April 9–13, 2025.

Marshall A. 2025. WHICH TREES HAVE CATKINS? AND HOW TO TELL THEM APART. Woodland Trust.

The Information Architects of Encyclopaedia Britannica. “catkin“. Encyclopedia Britannica, 1 Apr. 2025, https://www.britannica.com/facts/catkin. Accessed 1 April 2025.

Weakley AS, Ludwig JC, Townsend JF. 2012. Flora of Virginia. Botanical Research Institute of Texas.