Picture an orchard: what do you see? Most likely, you’ll see fruit-laden trees. But what is growing below and between the trees? And what is living in and around the them?
Recent research conducted at the University of Reading delved into the impact of growing wildflowers beneath apple trees on the insect population and how it influenced the apple crop. The insect community was compared within two different types of vegetation beneath the trees: a wildflower strip and a regularly mowed grass strip.
Why wildflowers?
The wildflower strips demonstrated significant advantages for ‘beneficial’ insects such as bees and aphid predators, which were notably more abundant in and above the wildflower strips, compared to the mowed grass strips. In fact, not only did apple trees above wildflower strips host more aphid-predators than those above mowed strips, but they also exhibited fewer aphid colonies and less apple damage.
In other words, the presence of wildflowers below the trees led to a better quality apple crop. The wildflower strips even had ‘spillover’ effects into a cereal crop being grown next to the apple trees, with a higher diversity of predatory bugs than next to the mown strips.
There were some interesting seasonal differences too, with the wildflower strips providing the most substantial benefits early in the season. This implies that wildflowers play a surprisingly crucial role for insects during the winter, despite not being in bloom. It is likely due to many insects needing dense vegetation cover to provide good protection from predators like birds to survive the winter.
Such protective cover is often scarce in excessively ‘neat’ environments where the grass is consistently trimmed and leaves are gathered, making it challenging for insects to find secure overwinter shelter.
Practical tips
If you’d like to give the useful insects in your orchard a helping hand, think about dedicating an area beneath or nearby orchard trees to wildflowers, and leaving some of this unmown over the winter. It is however a good idea to mow the wildflowers occasionally (once or twice per year) to prevent it becoming overgrown. If possible, avoid mowing all of it simultaneously to ensure that some protective cover is always available.
Future research
The above research was carried out at a farm that incorporated strips of apple trees into a cereal field. There is increasing interest in this type of agriculture, known as ‘agroforestry systems’, where trees are grown alongside other agricultural crops or livestock. This way of farming can bring many benefits, including soaking up carbon (therefore helping to slow climate change), restoring farmland wildlife, and increasing the resilience of farm businesses by boosting product diversity.
The University of Reading has a dedicated agroforestry research group, currently working on a Europe-wide project called ‘REFOREST’, which is finding ways to empower farmers to use trees to farm for food, carbon and biodiversity at the same time.
by Tom Staton, University of Reading – for more information on his research, check out his staff profile.
The Orchard Project’s research into agroforestry has been ongoing for several years, including as part of our Farming the Future project. In Wales, project manager Witchhazel Wildwood is overseeing the fruit tree rows at Cae Tan CSA, and alongside rows planted with herbs and perennial vegetables, they are also now creating a row underplanted with wildlflowers to enhance the biodiversity even further.
And you don’t have to be at farm-scale to employ similar techniques to encourage more biodiversity into your growing space – at GROWE in Manchester project manager Elsa Little has been working with the volunteers to plant guilds of herbs, wildflowers and other perennials within the rows of some existing fruit trees (see below). Just a few months after planting, they were harvesting mint, currants and strawberries and the yarrow is still in bloom, providing food for pollinators. There were also significantly more red admiral butterflies in this part of the orchard.
