27 July 2011/ 14 March 2012 OS Explorer 181 Chiltern Hills North SP797126
Length: Ten minutes.
Hartwell House is owned by the National Trust and provides accommodation and meals. The old parkland around it has a few old horse chestnuts and walnuts, but the distinctive feature is a patch of giant butterbur Petasites japonicus at the far end on the bridge over the lake north of the house. This plant was sometimes introduced to old estates, along with Gunnera and other exotic species, but there seem to be few places where it survives today. We examined the huge leaves on 27 July 2011, when the flowers had died away altogether. The underside of some of the leaves had the orange rust-fungus Coleosporium tussilaginis, which occurs more commonly on coltsfoot.
Giant butterbur leaves
There was amphibious bistort Persicaria amphibia in the water and water figwort on the banks.
Water figwort
Alder trees Alnus glutinosa near the butterbur had the galls of two mites on their leaves, Eriophyes inangulis along the midrib and E.laevis on the blade itself.
Alder leaf with mite galls
Underneath many of the alder leaves was the rust-fungus Melampsoridium betulinum, which more normally occurs on birch, but has been recorded on alder in Scotland . The rust causes pale raised patches on the upper side of the leaves.
Alder leaf with Melampsoridium betulinum (lower)
The bridge, incidentally, constitutes the central arch of the former 18th century Kew Bridge over the Thames , removed to Hartwell when it was demolished.
We visited Hartwell again on 14 March 2012 to see the flowers of giant butterbur. The transformation was incredible – the patch of huge leaves was entirely gone and breaking through the bare earth were tufts of white butterbur flowers subtended by very different small pale green oval leaves, each like a small cauliflower. They were attractive, but the succeeding leaves make them impractical for all but the largest gardens and parks.
We visited Hartwell again on 14 March 2012 to see the flowers of giant butterbur. The transformation was incredible – the patch of huge leaves was entirely gone and breaking through the bare earth were tufts of white butterbur flowers subtended by very different small pale green oval leaves, each like a small cauliflower. They were attractive, but the succeeding leaves make them impractical for all but the largest gardens and parks.
Giant butterbur in flower
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