ALNUS GLUTINOSA ‘IMPERIALIS.’ by
Then first rivers felt the hollowed alder,
And therewithal the light alder, sent down the (river) Po, swims on the bubbling wave - Virgil’s Georgics.
(Many thanks to Bella Image from Ripon College for the translation from the Latin)
I was pleased to hear at their last meeting the council had agreed to plant a cut-leaved alder (Alnus glutinosa ‘Imperialis’) on Denton Green as a replacement for the sweet chestnut which had to be felled.
I was introduced to the cut-leaved alder by a fellow fisherman on the banks of the river Loddon at Stratsfield Saye and he told me there were few established trees and these were mostly on large estates. I later saw some trees for sale at a local garden centre and now my fellow fisherman and friends have them in their gardens. It is a very attractive graceful tree with mid-green finely cut leaves and pale purple flowers.
It is deciduous, but like a lot of trees growing in wet soils, it will retain its leaves well into the autumn.
It is derived from the common or black alder (Alnus glutinosa) which is a native of Europe, including the British Isles, and grows in moist situations along the banks of rivers, canals and brooks, but I have seen it established on the spoil heaps of the mining industry in the rugged north. It is able to grow in poor conditions because nodules on the roots contain bacteria which absorb nitrogen from the environment and fix it into a form available to the alder and surrounding plants. This relationship, which improves the fertility of the soil has established the alder as an important pioneer species in ecological succession and the leaves make a nitrogen rich compost. Although not the same bacterium a similar symbiosis exists with peas, clover and other legumes which are used in farming and gardening to maintain fertility.
Browne refers to this benefit to other plants in ‘Brittania pastorale’:
The alder whose fat shadow nourisheth
Each plant neere to him long flourisheth
The male flowers are rather inelegant catkins and although mainly wind pollinated bees visit them to collect pollen for their spring build-up of the colony and butterflies collect nectar. The female flowers resemble small conifer cones and chaffinches and tree creepers rampage through the branches in search of food.
Alders were plentiful on the banks of the river Po and some of the earliest boats were hollowed out trunks referred to by Virgil. The timber was resistant to immersion in water and Vitruvius, a Roman architect, used it as foundations for buildings and it has been used for piles supporting structures in Venice
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