A catkin is a long cluster of very small flowers, none of which have petals.
From the dailyherald.com
A single walnut catkin, for example, releases about 2 million pollen grains.
From the dailyherald.com
They also have brown dots along the back that mimic the stamens on a catkin.
From the newscientist.com
A boy carries traditionally decorated catkin twigs during a Palm Sunday procession in Lofer, Austria.
From the washingtonpost.com
The inflorescence is a catkin up to 10 centimeters long.
From the en.wikipedia.org
Before catkin buds open, western boundary hedge gets trimmed lightly over its width and its height kept around 2m.
From the guardian.co.uk
The male flowers are catkin-like, up to 1 m long.
From the en.wikipedia.org
There are typically 10-30 seeds on each seed catkin.
From the en.wikipedia.org
Try as I might I cannot relocate it within its microworld and the more I handle its catkin inner sanctum the more it crumbles under my weight.
From the guardian.co.uk
More examples
A cylindrical spikelike inflorescence
A catkin or ament is a slim, cylindrical flower cluster, with inconspicuous or no petals, usually wind-pollinated (anemophilous) but sometimes insect pollinated (as in Salix). They contain many, usually unisexual flowers, arranged closely along a central stem which is often drooping. ...
A type of inflorescence, consisting of a slender axis with many unisexual apetalous flowers along its sides, as in the willow and poplar
(Catkins) A dense, often drooping flower cluster, consisting of small scale-like flowers aggregated into short, tubular spikes.
(Catkins) wanderingnome on Flickr
A pendulous or erect flower spike made up of bracts, each of which contains a single sex, stalkless flower.
A long flower cluster (such as on a willow tree).
A drooping cluster of flowers or fruits on a flexible axis (resembling the tassels on wheat).
Slender inflorescences made up of small flowers, usually reduced to the male and female parts. Catkins are typical of wind-pollinated trees.