The garden gender gap

Most plants are pollinated by insects, invertebrates and small mammals, but some rely on the wind to reproduce, thanks to some interesting botany. Harriet Carty, from Caring for God’s Acre, explains

Most flowers contain both male and female parts within the one flower, but wind pollinated trees usually have separate male and female flowers. These may occur on the same tree as they do in hazel or oak or sometimes on different trees for example willow and poplar.

The male flowers form in clusters making catkins, for example, whilst the female flowers stand upright individually. Both the male catkins and female flowers can be seen on the edges of the tree canopy where the wind will catch them, shaking the catkin, releasing the pollen and carrying it away.

The female flowers often have a sticky tip or ‘stigma’ to catch the passing pollen. They are sometimes red, looking a little like a small sea anemone. Once pollinated the female flower will develop into the seed, be it an acorn, pine nut or a hazel nut.

Wind pollination works well for trees that flower early, when few insect pollinators may be about, for trees that are found in cold and windy spots too. Hazel, birch, willow and pines are trees that are early to arrive and grow on bare, rocky ground and are thought to have been amongst the trees that first colonised patches left bare by retreating glaciers after the last ice age. Wind pollination would have been an advantage in this.

Another important group of plants pollinated by wind are grasses. Grass flowers tend to be green, yellow or pale brown rather than brightly coloured. They are produced at the top of a stem that usually stands vertical, bringing the flowers above other foliage and into the wind. They tend to be clustered, often in a spike rather like a vertical catkin and they produce a large amount of pollen which can be carried over distance.

Many grasses open up when ready to release their pollen, looking like a miniature Christmas tree, so that all of the flowers will be caught in passing breezes. Some grasses do have strong colours, but this is due to the colour of the pollen not the flowers. Grasses may be at their most beautiful when releasing coloured pollen. One example of this is meadow foxtail, so named because the red pollen colours the flowering spike like a fox’s tail.