Reclaiming a farm field for nature, ten years on: a progress report from Oxford and some tips for gardeners.
Haven’t we all dreamt of buying a little nugget of land to create a green or ‘environmentally friendly’ garden or wood?
Oxford University’s Botanic Garden and Arboretum (OBGA) was in the envious position in 2006 of adding Palmer’s Leys, a 50-acre field, (pictured left) to its Harcourt Arboretum in the village of Nuneham Courteney. The £185,000 required to purchase the field was raised by the Friends of OBGA.
50 acres equates to a big, big field. It would take 10-15 minutes for an average runner to run its border, for example. Palmer’s Leys is fortunately endowed with a gentle slope reminiscent of an Eric Ravilious print of the South Downs, recalling the Nuneham Park Estate that was created by the Harcourt family in the 1710s. You walk up a slope from the entrance to the Arboretum, and then look away and down Palmer’s Leys from a gentle ridge. It is also dotted with occasional oak trees of majestic girth and height, propitious features that couldn’t have been bought or grown.
Despite having previously been used for arable crops, recalls Guy Horwood, now Senior Arborist at the Harcourt Arboretum, the underlying soil was good even at the time of purchase, and the decision was quickly made to create a 30-acre wild flower meadow and a new wood of 13,000 British native trees.
Visiting Horwood and Ben Jones, Arboretum Curator, (Jones, pictured left) on a very rainy day in August, I’m curious to establish why these land-use were decisions were made and how ordinary gardeners can learn from them. Some of the answers turn out to be straightforward, almost brutally so.
‘Something like 97% of Britain’s semi-natural meadows have been lost to modern farming practices since the end of the Second World War,’ says Jones, ‘…yet they are home to a vast array of species native to Britain.’ The term ‘semi-natural’ is instructive here. It’s not the case that there was recently an unblemished, untouched tract of wilderness that was wrecked the minute humans turned up and the Anthropocene began, rather that woods were cleared for livestock and human habitation since 4000BC, by the Neolithics, in turn creating new habitats.
In a way that’s the first lesson for any aspiring eco-warrior gardener. Humans have been around a very long time. Leaving your imagined little nugget of land to simply choke itself isn’t going to be the best option, and it will not in any case return to a primordial state.
Even rarer in Britain than forest is the semi-natural wild flower meadow, so that became a priority for the arboretum.
The second decision to plant 13,000 trees was of course to address the need for more woodland as well, but in this respect a peculiarity entered the equation at Harcourt. Jones explains that the Harcourt estate has historically grown clusters of different species of tree rather than mixing them up, so he decided to honour that with sectioned areas of yew, hornbeam, whitebeam, ash, beech, oak and lime.
Criss-crossing the woodland are the sorts of wide, elegant rides that define the Arboretum and make for lovely walks.
What lessons have been learned ten years on? Jones notes that the upper slopes of the wood are relatively exposed. Natural regeneration of willow and birch has almost been too successful there, pointing to the need now for thinning, so as to allow other species to succeed. More worrying is ash die-back, confirmed last year. Jones says that in this respect there is very little that can be done. Of the 2-3,000 ash trees, the hope is that by leaving them to their own devices some will survive by developing a natural tolerance to the disease. More successfully, a large perimeter deer fence has mostly protected the younger trees – but not entirely. The slow-growing yews are mostly now above deer grazing height which is promising; oaks are at 6-10 feet, the beeches and limes double that and more.
The meadow has been a great success. The day I visited it had recently been mown, resulting in large, black plastic shrink-wrapped bales of hay all over the field awaiting collection. I thought I was in the wrong field but apparently this is precisely the point about a semi-natural meadow – wild flowers flourish in a low nutrient condition. The trick is to cut the weeds and mow for hay, but then let in sheep in a process called ‘aftermath grazing’. The sheep cut back excess grass and their hooves beat down seeds from species such as yellow rattle, helping them to take hold. Yellow rattle parasitizes grass and makes the way for other plant species to flourish. ‘There’s a big difference,’ says Jones, ‘between a weedy field and a wild-flower meadow.’
A huge moment came when someone spotted grass vetchling, a rare species in the pea family which produces tiny pink flowers. Other species that have thrived in Palmer’s Leys include ragged robin, common spotted orchids and marsh orchids.
Asked what tips he would offer alumni readers faced with such husbandry decisions, Jones notes, ‘You have to think a hundred years ahead. If you are planting a field maple try to obtain seeds with a provenance from the South of France rather than from Scandinavia: climate change should be at the forefront of these long-term decisions.’ Other decisions are far less clear cut but no less important. Initially, for instance, the decision was made to use a habitat friendly herbicide (check with the Soil Association or RHS) to cut back some of the unwanted species at Palmer’s Leys. Later on, volunteers worked their way across the field with shovels to remove thistle and dock, prolific in their ability to choke. ‘This was very labour-intensive but we decided not to use any herbicides once the meadow was underway,’ says Jones.
Apart from the capital expense of the field, the most expensive bit was the deer fence and then the wild-flower seed – not the fledgling trees as might be expected.
Drinking tea as we sit and discuss Palmer’s Leys inside the Arboretum staff room and kitchen, rain still beating down outside, I ask Ben to remind me what the broader aim of the Arboretum is, given that a collection of exotic trees might be dismissed as the show-off curio of a wealthy landowner.
He reminds me first that Oxford is firmly involved in a Millennium Seedbank project that intends to have a quarter of the world’s species banked by 2020. In respect of the Arboretum, the older field of unimproved grass and Palmer’s Leys, he notes that the whole is intended to maximize ‘the conservation of biodiversity’ and in turn threatened species. ‘If you ask anyone which species are most threatened they’ll say elephants or cheetahs or rhinos or gorillas; but no one can name a single threatened plant. Yet one in five plants are threatened with extinction.’
Botanic Garden and Harcourt Arboretum official website - www.botanic-garden.ox.ac.uk
Photos: University of Oxford/Richard Lofthouse