Insect sign and structures

Visit Knepp’s rewilded Walled Garden

The fine, fairy-tale spring continues and the Met Office reports it’s the sunniest in the UK since records began in 1884 – 653.3 hours of sunshine – and with very low rainfall. It is the driest spring in 100 years. Despite this, the garden swells, every day a new colour and flower shape adds to the joyous eruption, greens in fifty shades from grey to lime, rise and spread to sit shoulder to shoulder, building layers of structure. 

The yellow hues of late winter give way to blues and pinks –  tongues of Siberian iris fall atop stout stems (Iris siberica ‘Shirley Pope‘, ‘Ruffled Velvet’ and ‘Sparkling Rose’), the pendant cobalt bells of solitary clematis (Clematis integrifolia ‘Blue Ribbons’), garden storksbill and bloody cranesbill (Erodium manescavii and Geranium sanguineum ‘Max Frei’) and the cup-shaped simplicity of the delightful blue flax (Linum narbonense ‘Heavenly Blue’).  

We wondered how much this seasonal colour change is related to an increase in the number and diversity of insects at this time of year. The plant choices in both the Rewilded and Kitchen Gardens were made both for their self-seeding ability and their attractiveness to pollinators. Many pollinators, especially bees, see in the ultraviolet (UV) spectrum and flowers often have UV-reflective patterns called nectar guides that direct insects to nectar and pollen within the flower structure. Studies have shown that bees are generally attracted to blues, violets and yellows and that these colours are an indication of a rich nectar source. Butterflies prefer red, orange and pink flowers while beetles and flies tend to favour duller tones or stronger scents. In evolutionary terms, insect colour vision appeared long before flowering plants (angiosperms) and it’s believed that flowers evolved their visual signals to be in tune with the sensory systems of pollinators, becoming as conspicuous and attractive as possible. Having as diverse a range of colours in a garden, then, clearly helps support a diverse range of insects – a cautionary tale for garden designing with a limited palette. 

It’s the time of year when the garden surges with visitors – both wildlife and human – and Knepp’s ecology team, Matt Phelps and Fleur Dobner, carve out some time in their busy schedules to begin this season’s garden surveys. We were thrilled to discover they had seen a spotted flycatcher – most likely the same one that nested in the garden last year. Migrating from sub-Saharan Africa where they overwinter, they will often return to the same site, particularly if they were successful in raising chicks. The high walls surrounding the garden as well as their cloaks of honeysuckle, roses and clematis favour their feeding specialisation – catching flying insects in mid-air, launching into aerial agility from elevated perches, known as “sallying”. They often nest in tree cavities, ledges or in ivy or wisteria on buildings, and their numbers have been declining sharply in the UK. This is due to a combination of habitat loss, decline in insects and challenges during migration. Gardens can play an important role in their survival, preserving nesting sites and encouraging insect–rich habitats. Chiff-chaff, Eurasian wren, song thrush, greenfinch, goldfinch and cuckoo were some of the other wonderful birds Matt and Fleur recorded.  

A few weeks of moth trapping showed a good range of species in the garden – among them the more bizarre and beautiful – the chocolate tip, buff tip, and white ermine. 

Moths benefit from the long-grass areas left unmown in the meadows just outside the garden wall, and inside, where a diversity of species is planted. Charlie Harpur, our head gardener has had some fun mowing circles and patterns of pathways, so the meadows support a mix of short and long sward. Adult moths feed on grass flowers and many larvae feed on the stems. Just a small patch left to grow long in these reproductive months can make a difference, particularly when urban garden corridors are working together and creating mosaics of habitats and refuge. 

We’ve been spotting a real buzz of activity around the new structural elements we’ve added to the Rewilded Garden over the winter. The four new mounds of fine Thanet sand have proved to be prime residential locations for a little cloud of wasps, bees and flies. The small grains can retain a degree of moisture and allow for the creation of non-collapsing tunnels where eggs can be laid and hatched. The stag oak limbs that ring the potting shed terrace have been treated to an archipelago of small, drilled holes, as well as in the assortment of standing and piled logs through the planting. Within hours, the endearing heads of small bees could be seen peeking from the apertures. We await the brilliant mind of Dr Erica McAlister, senior curator at the Natural History Museum and expert in flies, to help us with some of the identifications. Meanwhile, it is a fascinating way to spend a few moments with nature’s extraordinary creations. 

In the Kitchen Garden, the benefits of structure come in the form of layered planting. In the no-dig veg beds Suzi Turner, Deputy Head Gardener in charge of edibles, has created beds with multiple layers – woody shrubs like currants, perennial herbs and annual vegetables like broad beans, salads, radishes and spinach in a single bed. The ground cover has prevented the soil from losing moisture, the planting density has deterred predation from pigeons and blackbirds, and promoted a diversity of root structures below ground that, in turn, encourages a diverse community of microorganisms.

The question of root functions within the soil was one of the many discussions that came up whilst chatting with some of the visitors who’ve been attending our planting workshops. A hugely complex subject, the relationship between plant roots and the soil biome have been subject to intense scrutiny for decades. However, the research is predominantly related to agricultural settings or studies of edible gardens, such as forest gardening or permaculture, with the emphasis on productivity. As gardeners, our concerns of below-ground activity also focus on how it is affecting the plant above – are there enough air-filled pores surrounding the root area (the rhizosphere) to allow gas exchange and uptake of water? Are there enough minerals and carbohydrates being made available to the plant by the actions of soil bacteria and mycorrhizal fungi to ensure healthy growth? Of course, these are all valuable elements in maintaining a healthy ecosystem. In this garden experiment, and rewilding in a garden setting, we often talk about a change in our mindset. How would it be to imagine the design of the garden in subterranean terms – a roots garden? As the climate changes, and stresses of drought, temperature swings and extreme rainfall bring challenges to gardens and their wildlife populations, the diversity of root structures, their shape, extent and chemical interactions with microbial life are likely to be an important factor in building resilience and longevity in gardens. 

As the month progresses the landscape swells, donning a thick coat of green, and the hedgerows fill with great frothy plates of cream-green elderflower. The warm dry days finally break, the skies a bruise of blackberry-stain, thunder edging its way towards us before the downpour breaks and we celebrate the gift of water, irrigating new plantings and seedlings. It ends with a visit from a legend, a man who created a garden called Wildside on the edge of Dartmoor, with complex topography and diverse habitats inspired by natural plant communities – Keith Wiley. We discussed sand in aggregate mixes or as mulch and its ideal consistency (demerara sugar), plant choices and inspiration. It was difficult to contain our pleasure seeing his enjoyment of the garden. He described it as an amalgamation of all that he loves in Mediterranean landscapes – a romanticised Crete. From a man who has been ‘wilding’ his garden for twenty years, who created a force of naturalistic beauty inspired by love, and entirely on his own, moved 100,000 tonnes of soil with a three-ton digger, a three-ton dumper, a wheelbarrow and a bucket, this is praise indeed. 

You can visit Knepp’s rewilded Walled Garden

Photos courtesy of Charlie Harpur, Moy Fierheller 

What we’re reading: 

About/Contact – Pleasant Place 

Genetic architecture of UV floral patterning in sunflower | Annals of Botany | Oxford Academic 

Pollinators show flower colour preferences but flowers with similar colours do not attract similar pollinators | Annals of Botany | Oxford Academic 

The Secret Life of Flies | NHBS Good Reads 

KBBS Beth Chatto symposium report 2 

Plant Roots | The Hidden Half, Fifth Edition | Tom Beeckman, Amram Esh 

Interactions between plants and soil shaping the root microbiome under abiotic stress – ScienceDirect 

WILEY AT WILDSIDE | Risk-taking in Landscape