The dry days persist, as does the incessant and unseasonable tugging of the north wind, occasional gusts surprising us with their ferocity and sending scented eddies of rose petals into the air. The sun bakes the sand and crushed concrete of the Rewilded Garden and reflects the heat. Graeme Lyons, who is conducting the first invertebrate survey of the garden since his baseline study before this project began in 2020, noted broadly that he has been finding more insects that thrive in hotter, drier conditions. We wait for the full report into his findings early next year, as Graeme will sweep the beds on repeated routes every month of the summer.
James Hitchmough, who designed the section of the Rewilded Garden now affectionately known as ‘Hitchmough Ridge’ paid us an impromptu visit to check on progress. His style of planting is heavily influenced by natural landscapes he has encountered in many parts of the globe. Densely packed perennials and bulbs jostle beneath ‘place dominant’ species like the pencil cypresses that provide architectural points through the planting. The global palette of plant choices hail from similar habitats – dry, stony riverbeds, mountain scree slopes, rocky deserts. This year, the plants that have grown from the seed mix of 43 species that were over-sown through the 9cm pot planting in November 2021 have firmly established themselves. Many are in full flower despite weeks without rain. An eye-catching array of beard tongues, that will only really grow in this country in these sorts of free-draining, nutrient-poor substrates, are thriving. The broad-leaved beardtongue (Penstemon ovatus) appeared first, its pale blue panicles of tubular flowers busy with the hum of buff-tailed bumble bees. The cobaea and large beardtongues (Penstemon cobaea and P. grandiflorus) were smothered in generous purple and pink trumpets competing for attention at knee-height all along the ridge, spilling into the opposite sides of the paths. James was pleased – many of his more established meadow designs have reduced in species diversity from their original planting. It is a cautionary tale for us. The importance of disturbance and selective herbivory will be key to preventing this garden becoming filled with a few dominating species. In future, we’ll need to be bold in the decisions we make as the keystone species in the garden.
Broad-leaved and cobaea beardtongues in the Rewilded Garden (Penstemon ovatus and Penstemon cobaea)
We’ve been pleased to receive a steady stream of visitors this month who’ve kindly offered their help while learning a little more about the garden. The exchanges are always enjoyably mutually beneficial. Paul Aston and Ciaran Bradshaw, who are hoping to develop a small-scale project of their own to address some of the challenges of climate change and horticulture, joined us from Cambridge Botanic Gardens. In turn, we received some much-needed advice on a few species of orchids we’ve inherited. Jac Semmler, a designer and author from Australia dropped in for a day on a whistle-stop tour of the USA and the UK. She had encountered some of the plants in the Rewilded Garden in their natural habitat in California and Oregon. Catriona Hood, studying the Specialist Certificate in Kitchen Garden Production at Kew, divided a week between us and the market gardeners. She shared ideas with us for some of the more unusual annual climbing vegetable varieties she is working with at Kew. Mashua (Tropaeolum tuberosum), for example, is part of the nasturtium family, and there is evidence of edible use of these plants’ tuberous roots up to 8000 years ago. In modern cooking, it’s treated rather like a turnip, while the leaves and flowers can also be eaten in salads. Oca (Oxalis tuberosa) is native to the Andes, producing tubers in vivid colours of red, yellow and orange, and jicama (Pachyrhizus erosus) is a vine up to 20 feet tall, but again, it is the tuber that is eaten. Used in Mexican cuisine, it can be flavoured or marinated and eaten raw as, despite its potato-like appearance, it is actually part of the pea family. Yacon (Smallanthus sonchifolius) is as ornamental as it is useful, related to sunflowers and dahlias. Similar to a Jerusalem artichoke, its edible roots are described as sweet, crisp and juicy, eaten raw like a fruit. A host of exciting experiments we can look forward to trialling in next year’s growing season.
After weeks without rain our focus inevitably turns to the question of whether we should be irrigating the garden or allowing natural processes to drive the ecosystem. Temperatures languish in the high 20’s for weeks and by the afternoons, many plants respond with drooping heads in a dejected state, their forlorn leaves curling inwards like shoulders of the defeated. The Kitchen Garden’s established plants are more robust, densely packed, creating their own humidity, shielding the soil from moisture evaporation. In the dirty paths where the cap of Breedon gravel over a topsoil and gravel bed protects roots from the heat, the Mediterranean herb planting appears entirely unperturbed by the temperature. The Rewilded Garden, in contrast, is doubly heated, with the sand and crushed concrete both retaining heat and reflecting it back onto the plants. Some are only a year in the ground, others just emerging this spring from seed. Although larger areas of bare ground between plants are an important habitat for many ground nesting bees, they compound the lack of humidity and a few of the plants are showing signs of strain.
Two pathways present themselves: we allow the natural process of a state of drought to dominate, causing increased stress on the plants, appreciating that this is one of the ecological influences on vegetation in a natural landscape; or we irrigate the garden (using tripod sprinklers) on those areas that are struggling or where we have recently added new plants grown from seed.
In the first instance, we run the risk of losing so many plants that we reduce complexity and limit the diversity of food sources for insects. One garden safari visitor questioned whether the quality of the food source might be improved for insects if the plant was sufficiently hydrated to function effectively. Arguably, we might be introducing alternative habitats for saprophytes (organisms that live on decaying matter) or shelter and shade for invertebrates by leaving plants to die in situ. We may be surprised by what species might colonise an area as others decline. As horticulturalists, often our driving motivation is care, and it is a difficult thing to suffer a plant to die when intervention is possible.
In the second instance, we are mindful that this project is still young, that we are in the establishment phase, and releasing our hands from the steering wheel should happen a little distance down the road. There is the question of sustainability – how long we can reasonably use a dwindling and increasingly costly resource like drinking water? This garden is an experiment; how are we to measure the efficacy or ‘success’ of this style of planting in the face of climate change if irrigation is still required? After much consideration it was decided that, with the project in its infancy, some plants were too immature to have set down roots sufficiently to survive and we watered those specific areas.
Our remit as custodians is to discover how and if it is possible to create a rewilded garden that is both biodiverse and beautiful, that allows natural processes, with us as the agents of disturbance to produce a dynamic ecosystem. Our simple conclusion in the end: only time will tell.
Moy Fierheller Deputy Head Gardener June 2023
Photos courtesy of Karen Finley, Charlie Harpur, Moy Fierheller
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