Climate & topography
The 4 hectare (10 acre) arboretum is in the heart of the Chilterns on the edge of
Berkhamsted (NGR SP 978 069). When it was purchased in 1997 it was a bare field which had been used for fattening beef cattle. The field had come onto the market because the building of the A41 road, that by-passes Berkhamsted, cut off the field from the farm of which it had been part. Two sides of the field are flanked by Hockeridge Woods owned by the Royal Forestry Society. Part of another side has a Christmas tree farm. Two roads with tree-lined verges run alongside the remainder of the borders. The Royal Botanic Garden Edinburgh has designated the arboretum as a safe site for ex-situ conservation. Trees do well in the Chilterns.
Beneath a shallow topsoil of some 20cm (8”) to 50cm (20”) the ground is a mixture of clay, chalk and flint. It has a pH of 5-7 i.e. acidic to neutral.
The arboretum has a mainly south-westerly aspect. The ground is for the most part on a slope. The bottom is some 150m (500’) above sea level rising to around 162m (550’).
The climate is typical for the United Kingdom, that is it is temperate; moderated by
prevailing southwest winds. More than half the days are overcast. Precipitation as daily
recorded over 2018-2022 was, in millimetres:
| 2018 | 2019 | 2020 | 2021 | 2022 |
| 541 | 700 | 861 | 592 | 591 |
The considerable fluctuations mask the fact that in each year there were extended dry
periods with no or negligible rainfall. To provide water in dry periods a leaky hose and
micro-drip irrigation systems have been installed.
When Kevin Martin (Head of Tree Collections, Kew) visited the arboretum one of the things discussed was losses of trees through drought in 2021 (which was before the irrigation systems had been installed). Beulah had lost very few, mainly some sickly maples whereas Kew had lost many trees. Kevin thought the difference in the proportions of losses was probably attributable to Beulah’s soil being largely clay which would retain moisture better than Kew’s sandy soil.
The top of the field is also the top of the hill of which it is part, the field has day long
sunshine. Using the output from solar panels as a proxy for the amounts of sunshine in
Berkhamsted, in KWH, we have had over the last 5 Years:
| 2018 | 2019 | 2020 | 2021 | 2022 |
| 1468 | 1486 | 1594 | 1363 | 1588 |
The figure for 2012, which is when the records began, was 1,416. It would not be
reasonable to draw any firm conclusions from these figures, but they are indicative of
gradually rising temperatures which, if continued indefinitely, and taking into account the life span of trees, bodes ill for the long term future of some if not many tree species.
