The thickest giant sequoia of England can be found in Cowdray Park, West Sussex. Cowdray is a vast area that was a deerkamp during medieval times, and a lot of large, ancient trees can be found there. Concerning the many trees in Cowdray Park, the non-native giant sequoia is definately not the most interesting: those are the native trees that have been growing there for centuries.
Many old oaks and a few huge Sweet Chestnut trees are growing in Cowdray Park, like the Queen Elisabeth Oak and the "Cowdray Colossos" Sweet Chestnut.
The giant sequoia avenue of Cowdray House
The largest giant sequoia has a girth of 9.56 m or 31.36 ft (measured at 1.5 m or 4.92 ft) and can be found at the southern end of the long Giant Sequoia avenue. This does not come as a surprise, because at that spot there's less light and root competition.
The Giant Sequoia avenue of Cowdray House. Most of the trees in this avenue have a girth between roughly 5 to 7 m (16 to 23 ft). While the thickest of them might be the giant sequoia with the largest girth of England, in the list of Giant Sequoias for the entire United Kingdom, this tree only comes in tenth place. That's just the way it is: Giant Sequoias are softwood trees and those do much better in rainy Scotland. The top 10 list consists entirely of Scottish specimens, not considering the English tree of Cowdray, two Welsh specimens and one Irish tree.
The Queen Elisabeth Oak
Without any doubt, the most famous tree of Cowdray Park is the Queen Elisabeth Oak. Purportedly, Queen Elisabeth I would have visited this tree in 1591, which was at that time already an impressive tree. At 1.5 m, this Sessile Oak (Quercus petraea) has a girth of 12.6 m, which makes this tree second thickest tree of its kind in Europe.
According to Jeroen Pater this tree is probably about 600 to 700 years, while according to dendrologists of the British Tree Register, this tree might be almost a 1,000 years old.
As you can see, this ancient tree is entirely hollow and has a very low crown. The shape of the crown is probably the result of the fact that this tree might have been a pollard, so this tree was, centuries ago, pruned heavily at least once. Because of that, the beauty of this tree is appreciated less than that of Majesty, a large English oak (Quercus robur), that was never pruned.
The Cowdray Colossos
Further in the park, in a somewhat hidden corner, a huge Sweet Chestnut tree is growing. What a monster.
According to the British Tree Register, this fairly unknown Sweet Chestnut tree (Castanea sativa) is the largest tree of its kind in England.
Other Sweet Chestnut trees are thicker, but have lost their full crowns for many years. Others can be taller, but do not have such a massive trunk.
This fast growing giant with a girth of about 12 m (36.4 ft) and a height of 26.5 m (86.94 ft) has lost some large branches of its own, but still makes a very healty impression.
The Dutch tree specialist Jeroen Philippona and me instantly referred to this tree as the "Cowdray Colossos".
When you're around, this tree is definately well worth the visit.
Left
In line with the giant sequoia avenue, but on the other side of the A272, there's a fabulous avenue of London Planes. A number of branches, resting on the ground because of their weight, have rooted and have become large planes themselves. While this is normal for for example Western redcedars, I have not seen many London Planes showing this behaviour. The avenue continues for hundreds of meters and changes slowly into a more classical Lime or Linden avenue.
Right
Along the same road, still in Cowdray Park, another remarkable Sweet Chestnut is located. Seen from the road, this tree with a massive turned trunk, may not seem very impressive, but when you come closer to the tree, it appears to be rather large. This tree was dubbed "The Elephant" by Jeroen Philippona (9.57 m at 1.5 m and a height of 24 m). I'm standing right of the trunk to add a sense of scale to this tree.
Visiting the park yourself?
Cowdray Park is rather large and is situated between Petworth and Midhurst/Easebourne.
Next to a pond on the north side of the A272, there's a small parking lot. This is the best place to stop if you want to visit the Queen Elisabeth Oak and the Cowdray Colossos Sweet Chestnut.
The London plane and giant sequoia avenue can be found a few hundred meter further along the same road, close to the entrance of the private Cowdray House (where a large Lebanon Cedar can be found).
More photos and information can be found on Jeroen Philippona's website.