Seeing my first hazel catkins of the year is another one of those defining moments showing that the sap is definitely rising and spring is on its way. Hazels are trees that are often found in hedgerows, so you may have only seen brief glimpses of the catkins by the side of the road as you drive past. Now we have more time to explore, why not go and seek out some hazel catkins and have a closer look.
Hazel trees are monoecious, meaning that both male and female flowers are found on the same tree. However, they do not self pollinate, and must be pollinated by pollen from other hazel trees. The yellow male catkins appear from mid-February, hanging down like clusters of yellow lamb's-tails. These are the male reproductive parts of the tree; each catkin has about 200 male flowers on it, each covered by a scale. When the tree is ready to release the pollen, the scale lifts and the pollen dispersed by the wind. You can see all the individual scales in the picture above, and towards the top of the catkin, you can see the green stamens (4 under each scale) which contain the pollen. Once the pollen has been released these stamens turn brown.
The female flowers look like small buds (see below), and have crimson stigmas that protrude when they are ready to receive pollen. The flower buds are located on the branch above the catkin, to avoid self-pollination. Once pollinated by wind, the female flowers develop into oval fruits which hang in groups of one to four. They mature into a nut with a woody shell surrounded by a cup of leafy bracts (modified leaves).