As a Visitor Guide at Kew, I have the privilege of getting up close and personal with a very fine collection of plants of all shapes and sizes. Today, I would like to introduce you to the giants of the plant world – champion trees. These are the big boys that grow larger than any others in their species, and the good news is that Kew Gardens proudly boasts more than 300 of them.
Before you think that to be a champion, a tree has merely to be really tall (and skinny) the formula is a little more complicated. Subjects are carefully assessed by volume of wood so are more likely to be biggest rather than tallest Results are then compared with what is ‘normal’. Some champions can come in at a mere two metres.
Take the genus oak as an example, comparisons are not made at this point – we need to go down to species level to really start to compare measurements; eg English oak (Quercus robur ), sessile oak (Q. petraea), cork oak (Q. suber), chestnut leafed oak (Q. castaneifolia) etc. before any results start to make sense. It’s this latter oak (Q. castaneifolia) that is one of my favourite champion trees at Kew. Measuring around 39m, it towers more than nine metres above the norm, and could even be the tallest chestnut leafed oak in the world!
This tree comes from Iran and was planted in 1846, so in oak terms it is still quite young. It’s champion status remains in the hands of its carers, but then Kew does have the best green fingers in the world.
Measuring trees is not only to find the largest and tallest specimen of what are the biggest living things on our planet, but studying a species at the extremes of its range can teach us much more than those that are average.
Measuring is all in a days work for the volunteers at the Tree Register of Britain and Ireland, more often referred to by its acronym TROBI. Their listing is an impressive database of more than 150,000 notable trees.
The golden rule is that the tape should be wrapped around the trunk at 1.5m (5ft) from the ground. Over the years methods to take height measurements of these giants have been wide and various but today laser gizmos make life easier. On young trees, these stats are taken every year whereas larger old trees can be measured every five to ten years.
Do look out for those blue champion tree labels at Kew!