Sunday, 16 October 2011
This tree is 620 years old
And the next one is about 390 years old, even though it looks like it should be older. They are both growing near the mansion at Wakehurst Place.
They are both Yews (Taxus baccata), two of five that we had dated by a Dendrochronologist - someone who counts tree rings. The modern Dendrochronologist doesn't chop a tree down to count its rings, of course. Instead they drill a small core for the trunk, very carefully and without allowing fungi and other nasty creatures to attack the tree.
The basis idea is to find and tally the 'annual growth rings' inside the bark. Larger wood cells (xylem) with thin walls are produced at the start of the growing season and smaller, thick-walled cells towards the end. In cross section you can see the transition easily between the end of one season (winter) and the start of the next.
Things get more complex, and accurate, by comparing trees in nearby areas and comparing dead and living trees to help fine tune the dating. In the UK there are now tables of dated trees (dead and alive) going back to 5289 BC.
Some of the oldest trees in the UK (and indeed in the world) are Yews. There are definitely some over 1,000 years old. The biggest (although not necessarily the oldest) are up to 28 m high and with trunks up to 17 m in circumference. They hollow out when old and don't necessarily put on growth for every year of their life. Which all makes it a complicated business dating a tree (and I'll avoid jokes about buying flowers and chocolates).
But back to our Wakehurst Place 'old lions' (as the venerable trees growing at Kew Gardens are called). Not only are they interesting because they are older than you and I, older than European settlement of Australia (223 years ago) and older than Kew Gardens (now 252 years old).
According to the Head of Wakehurst Place, Andy Jackson, their position provides some evidence of a garden constructed before the mansion. The two Yews line up with the current regular lawn and terrace in front of the house and the 1391 tree is on a human constructed terrace.
The land was owned by the de Wakehurst family from 1205 so it seems that these Yews may have been planted as part of the first garden development on the site. Alternatively the garden may have have been created around at least one naturally occurring tree.
And the Yew does occur naturally - you can find craggy specimens wrapped around rocks in more natural parts of Wakehurst Place. These are probably only a hundred years old or so...but very pretty.
More widely, the Yew grows throughout Europe and from North Africa to Iran. In the south of its range it grows mostly in mountains. In the UK and other northern areas it grows at lower altitudes and often in rugged locations such as above, rather than on the edge of neatly mown lawns as further above... As the sign says, it's rather common hereabouts.