When trees become a forest

A NEIGHBOUR of mine has a large garden and about 30 years ago he planted a lot of trees in it. The trees grew well, perhaps a little too well, and he became uneasy about the fact that they were starting to crowd him out. I was called in to give my opinion.

“Should I get rid of those?” he asked, pointing at a line of evergreens on the garden boundary.

The trees in question were Monterey Cypress, more usually known in this country as Macrocarpa from the Latin name of Cupressus macrocarpa. They were quite widely planted around the middle of the last century, particularly in coastal areas because they have a resistance to salt winds. In more recent times Leyland and Lawson Cypresses have become more popular.

They’re an interesting tree. Their native range is tiny. A narrow strip of the Californian coast near Monterey that is only three kilometres long.

Another tree, the Monterey Pine, is also confined to this area. There are only a few hundred wild cypresses and most of them are small and stunted things, more like bushes than trees, clinging to the sea cliffs.

The reason for this is almost certainly that this little strip was an ice age refuge. When the ice sheets swept down over the North American continent a warm ocean current kept the strip mild enough to preserve the trees. And, for some unknown reason, when the ice retreated the Monterey Pine and The Monterey Cypress failed to take advantage and re-colonise the surrounding area.

During the last ice age in Europe it’s probable that there was a similar refuge in south west Cork and Kerry that preserved the so-called Lusitanian flora and fauna. The Arbutus survived there and, like the Monterey Cypress, was not very successful in extending its range after the ice melted —- though it did make it up at least as far as Co Sligo.

But we know from analysing pollen records that many commoner tree species colonised Ireland from the south west rather than across the land bridges that connected us to Britain and the continent eight to ten thousand years ago. This is pretty conclusive proof that the refuge existed, unless, of course, you prefer to believe in the legend of Atlantis.

The refuge protected animals as well as plants. The Natterjack Toad and the Kerry Slug still live there. And recent DNA analysis suggests that the red deer in the Killarney National Park have been separated from the red deer of the rest of Europe for a very long time and also survived the last ice age in the south west.

THE MONTEREY Cypress was first cultivated in England in 1838 in the Horticultural Society’s garden at Chiswick. The seed was presented to them by a man called AB Lambert, but nobody knew where it came from. Then, in 1846 the Society employed a gardener of German origin called Theodore Hartweg to go on a plant collecting expedition to Mexico and California and he discovered the native stand.

The species became quite popular due to the odd fact that although it was a runt of a thing in the wild it became quite an attractive specimen in European gardens. It was also discovered that it was frost hardy despite the fact that it came from a place where frost was unknown.

I explained all these interesting things to my neighbour until his eyes started to glaze over.

Unfortunately, my mission was a failure. Next time I was passing I heard the sound of a chain saw. I stopped in to tell him that Monterey Cypress makes lousy fire wood because it sparks all the time, though if you have an enclosed stove it does produce pleasantly resin-scented smoke.

* dick.warner@examiner.ie

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