Tuesday 20 March 2018

Alder trees put on their lovely display of catkins

Catkins and last year’s female cones on an Alder tree
Catkins and last year’s female cones on an Alder tree

Jim Hurley - Nature Trail

Alder trees are not disappointing this year; they are putting on their usual excellent display of catkins.

In a simple world, the flowers of all Irish plants fall into two distinct groups: those that are pollinated by insects and those that are pollinated by the wind. The insect pollinated ones have showy flowers and a sweet smell to attract the insects that transfer the male pollen to the female flowers.

Those that are pollinated by the wind don't need to be either showy or sweetly perfumed to attract the wind. The wind blows regardless of the flower's shape or scent so wind pollinated plants have evolved flowers in the form of catkins as found on Alders and Willows.

So far so good. However, consider Daffodils in flower beneath an Alder tree. The Daffodil has a showy flower and often a sweet smell so it is obviously pollinated by insects. Right? Not so, unfortunately. Check Daffodil flowers for the presence of pollinating insects and you will find that they are few and far between.

The hand of Man must be factored in. Most Daffodil flowers are produced by plant breeders to meet market demands and the criteria of flower show judges for shape, symmetry, colour and scent. In the process, lovely shapes, colours and scents have been produced to please human tastes.

Very few insects are flying now and very few of them will bother visiting Daffodil flowers as they don't find them attractive. Consequently, Daffodil seed is a rare commodity; most are reproduced asexually via their underground bulbs. However, some Daffodils are managing to self-pollinate or wind-pollinate. Evolution is an on-going process.

Male Alder catkins are particularly attractive at present. They are bright yellow in colour and are long and dangling. They hang in great numbers from the leafless branches of the trees. They toss and turn in the breeze scattering great quantities of fine, dust-like pollen.

In contrast, female Alder catkins are red in colour and are small, short and stubby. They are sticky so pollen grains floating in the air get stuck to them resulting in pollination and the growth of olive-shaped, green, woody cones that are the tree's seed-bearing fruits. When the seeds are ripe, the cones open and shed their precious cargo of seeds.

This year's male yellow catkins may be seen on Alder trees at present together with the remains of last year's brown female cones.

Sligo Champion