Tree Identification by catkins

There are a number of trees that bear catkins in winter or in spring (before the leaves). A catkin is a cluster of unisexual flowers that have no petals. On wind pollinated trees, most catkins are long and thin and hang down below the shoot. These are found on Oak, Poplar, Birch, Alder, Hazel and Hornbeam but female Alder catkins are cone-like. On insect pollinated trees, like the Goat Willow, catkins may be short and fat. The Sweet Chestnut has an upright male catkin that emits a strong smell to attract insects. 

Tree identification by catkins – size, colour and flowering time of male or female catkins on 17 different species are shown here by 25 photos. Male catkins release pollen then drop off. Female catkins collect pollen, produce seeds over several weeks and then release the seeds. The catkins are easy to see and sometimes quite brightly coloured, so use these photos to identify the trees. Most trees bear their catkins for a short time – usually a few weeks – so the period February to May is probably the best time to use this means of identification. Alders have catkins in some form all the year. They shed pollen in February/March.  Some trees have male flowers on one tree and female flowers on another tree. Others, such as Alders and Hazel have male and female flowers on the same tree.

Click on any photo to enlarge it. To learn more about why trees have male and female catkins on the same or different trees click HERE .Click HERE for a detailed description of how catkins work. Click HERE to learn more about Pollination

Common Alder male catkins

ITALIAN ALDER male left female right  (February)

Common Alder female catkins

COMMON ALDER male left female right  (February). Female cones are smaller than those of the Italian Alder and larger than those of the Grey Alder.

Common Hazel male catkins

MALE HAZEL (late Feb) – see also Turkish Hazel

Aspen female catkins

FEMALE ASPEN (early March)

Aspen male catkins


Black Poplar female catkin

FEMALE ASPEN (mid March)

Black Poplar male catkins

MALE BLACK POPLAR (early March) 



FEMALE WHITE POPLAR  (March above/April below) Male trees are rare

HYBRID BLACK POPLAR (male catkin above-March), female catkins below – April)

CAUCASIAN WINGNUT – female left, male right (end of April)

HORNBEAM male catkins  (mid April)

HORNBEAM female catkin (August)

WALNUT male catkins (mid-May)

ENGLISH OAK male catkins (May)

SESSILE OAK male catkins (May)

TURKEY OAK male catkins (May)

HOLM OAK male catkins (May)

Goat Willow male catkins

 GOAT WILLOW male (early March)

Goat Willow female catkins

 GOAT WILLOW female ( left mid April, right end of May shedding seeds)

WHITE WILLOWY male catkin (April)

CRACK WILLOW female (May) shedding seeds