When scientists at Sheffield University conducted a survey of 161 gardens, the positive influence of a tree or large shrub on biodiversity was overwhelmingly obvious. No matter how big or small the garden, or how close to the city centre it was, the presence of a tree increased the numbers of almost every type of invertebrate counted. And where there are invertebrates, there are all the other creatures that depend on them.
A tree increases the space available for wildlife in your garden because it extends your garden upwards. It also increases the number of different habitats. Trees provide bark, dead wood, shady areas and leaf litter and their branches hold food in the form of buds, flowers and fruit.
The type of tree you choose will depend on soil conditions and the size of your garden. You can find details on a huge variety of trees that attract wildlife on the Woodland Trust’s website and their blog ‘British Trees To Plant In Your Garden’ but here are a few of our personal favourites from the best of the bunch:
Hawthorn (May/Quickthorn) grows up to 15m tall but can be kept much smaller (traditionally used for hedging, hawthorns can tolerate regular and extensive pruning). Their dense and thorny structure makes an ideal nesting area for birds like thrushes and dunnocks. In the spring, white flowers provide pollen and nectar for pollinators, and red berries in the autumn are a feast for migrating birds like redwings and fieldfares. You can expect your Hawthorn tree to grow between 40 and 60cm each year.
Rowan (Mountain Ash) grows to a similar size, at a rate of 20 to 40cm a year. Its flowers are less popular with insects than those of Hawthorn, but it has attractive foliage, especially in autumn, and lacks thorns. When the berries are produced, they are gorged upon by birds. Waxwings are particularly fond of Rowan berries. A slim tree, the mountain ash fits nicely into a small garden. It prefers a well-drained soil and doesn’t like shade.
Crab Apple restricts itself to a height of up to 9 metres and grows about 30cm a year. In spring, white or pink flowers make it a beautiful tree to have in your garden. Bullfinches find the buds particularly appetising, but if you are lucky enough to be visited by these shy birds, sacrificing a few flowers is a price well worth paying. As well as providing fruit, the foliage of the crab apple is eaten by many moth caterpillars.
Keeping a young tree well-watered and staked is absolutely essential to help them establish in their new position. Autumn and Spring are the best seasons for planting a pot-grown tree or November to March for a bare-rooted one. If you are planting a large tree, follow these steps:
- Dig a hole two or three times as wide as the rootball.
- Soak the rootball thoroughly and then tease out some of the roots to encourage them to grow outwards.
- Place your tree in the hole, making sure the place where the trunk meets the roots is level with the surface of the ground.
- Refill the hole and firm the ground.
- Water thoroughly and cover with a layer of mulch, leaving a gap around the trunk.
- Hammer a stake into the ground at a 45o angle and secure it to the trunk. Make sure the stake is in far enough – it needs to prevent the wind from blowing the young tree so much that the roots cannot establish a firm hold.
- Make sure the tree gets plenty of water during its first few months and in long dry periods while it is still young.