Programme four: Trees and Shrubs

The widest range of species is often found where two habitats meet - where woodland grades into grassland for example, where tall trees give way to shrubs and then wild flower meadow. 

The varied heights of trees and shrubs, with its variety of feeding opportunities, make this a varied and particularly attractive habitat for many birds, like tits and warblers, and for butterflies like the speckled wood, which will breed in gardens.

It's easy to recreate something similar, with its constantly shifting mosaic of dappled sunlight and shade, simply by creating storied layers of vegetation in the garden.

Many birds like to nest in mature trees but even young trees are good places to mount nest boxes. If you plant native tree and shrub species that have a rich and diverse insect fauna, like birch, mountain ash (rowan) or hazel, blue tits and robins will visit them to collect caterpillars for nestlings. 

Blossom trees like cherries, plums, pears and apples provide nectar and pollen for bees in spring and rotting fruit for autumn bird visitors and even for butterflies - peacock and red admiral butterflies love to drink the juice of over-ripe plums.In mature gardens old trees and even tree stumps are also a very valuable wildlife resource in their own right, sometimes attracting more exotic birds like great spotted woodpeckers and treecreepers that search for insects on dead branches and bark crevices

Looper caterpillars

Looper caterpillars move forward by drawing their tail end forward, so that they throw their body into a loop, then gripping with their tail and stretching out their head-end. They are the larvae of moths known as geometrids, so-called because they seem to be measuring their movements with geometrical precision (which also accounts for their other name: inchworms.

Most trees and shrubs will have larvae of one of the many species of geometrids feeding on their foliage. They are a major component in the diet of blue tits and great tits during the breeding season; a pair of great tits need to find up to 700  per day to feed their brood by the time they are about to fledge.

Many geometrid larvae are amazingly well camouflaged, resembling dead twigs or matching the colour of leaves. When danger threatens they often 'freeze', remaining perfectly still and relying on their cryptic colouration to escape detection.

Spot the caterpillar (above): almost a perfect match!

Not all geometrids rely on camouflage. The larva of the magpie moth is brightly coloured. Birds that try to eat it find it distasteful and the warning colouration acts as reminder that they shouldn't make the same mistake twice.

White-lipped Snails

These striped snails will often climb into bushes either to graze on the algae that grows on the stems or to spend the driest months of the year in a state of dormancy called aestivation. Then they seal their shell opening with a layer of dried mucus and glue themselves to the stems.

White-lipped snails come in a variety of different shell colour banding patterns. Some, found most often on sand dunes, have no shell bands at all. The frequency of the different types varies from place to place and is thought be be related to camouflage (they are favourite food of thrushes), although exposure to sunshine may play a part to - snails with broad dark bands tend to heat up faster, plain pale shells are less likely to overheat.

Plant Galls

Bedeguar gall (aka moss gall) on wild roses

Wild roses in hedgerows often carry these mossy crimson growths, known as bedeguar or Robin's pincushion galls. They are caused by a tiny wasp that lays its eggs in leaf buds, inducing them to produce a mass of tissue where its grubs can grow and feed on special nutritive tissue that the plant produces.

This is the minute wasp that causes the growth, Diplolepis rosae. A large bedeguar gall will contain over thirty developing larvae but many never reach maturity because....

..... they are parasitised by this minute but deadly ichneumon wasp.

As the poet Jonathan Swift quipped:

"So nat'ralists observe, a flea

Hath smaller fleas that on him prey;

And these have smaller fleas to bite 'em

And so proceeds Ad infinitum."

More Galls

The strange growths on plants known as galls are induced by a variety of different organisms including fungi, flies and microscopic mites but the most elaborate are caused by gall wasps. The pink flying saucer-shaped galls and those that look like golden embroidered silk buttons on the oak leaf below are caused by two closely related species of gall wasp. The pink spherical gall is caused by a third species.

Some galls can be very destructive. This is the knopper gall, caused by a gall wasp that lays its eggs in very young acorns and causes them to develop into a gall that looks like green popcorn. Knopper gall wasps spend half of their life cycle on native oak trees and half on the introduced Turkey oak, which is cultivated in parks, botanic gardens and arboreta, so you tend to find knopper galls most frequently where the native and introduced oaks grow in close proximity.

This is the marble gall, accidentally introduced in the early 19th. century when the called, which are rich in tannin, were imported for the leather tanning industry. Here the wasp lays its eggs in a leaf bud, which develops into a woody sphere with the developing wasp inside. The exit hole, where the wasp has hatched, is clearly visible here. Blue tits learn to peck into these galls to eat the grubs in winter, when other food is hard to come by.

Several trees, such as sycamore, maple and alder (above) carry large numbers of small red pimple-like growths on their leaf surface in late summer.

These are pocket-like ingrowths caused by minute mites that feed and breed inside. Here you can see them emerging from the mouth of the pocket on the underside of the leaf, and .....

.... here you can see them highly magnified, under a microscope.

Native Trees for a Wildlife Garden

Native trees are a rich resource for insects, which use them as a food source, and for birds that feed on the insects. Large forest trees, like ash, oak or lime grow too large for all but the grandest gardens by there are several smaller natives that fit comfortably into a plot of any size and can even be grown in large containers.

Silver Birch

Attractive white bark, small leaves that turn lemon yellow in autumn and a graceful pendulous habit all year round make this a particular attractive species. It supports more species of insect than any other native tree apart from oak, so is a favourite feeding site for hungry blue tits and great tits in spring and summer. Over 80 species of moth caterpillar alone feed on its foliage. 

In spring the tree produces these long, slender catkins from the tips of its twigs and..... 

.................in autumn silver birch trees carry catkins of small seeds that are a good source of food for ....

..... siskins ......

...... and redpolls. Once the supply of birch seeds runs out they'll turn their attention to your bird table if you supply niger seed.

Rowan, also known as Mountain Ash

Rowan, also known as mountain ash, is an excellent native tree for wildlife gardens because it does not grow very large or cast too much shade and it also flowers when just a few years old. It's an all year-round wildlife resource.

Rowan blossom, which has a distinctive scent, appears in early summer and provides a rich nectar and pollen source for many insects, including wild bees.

Many hoverflies, like this Leucozona lucorum, live on a diet of pollen, so the dense masses of rowan flowers is a valuable resource for them.  

Rowan produce heavy crops of berries which ripen in early autumn. Blackbirds are particularly fond of them. 

The Value of Old Trees

As trees mature their smooth bark develops deep fissures that are home to spiders and a host of small insects that attract the attention of hungry nuthatches and tree creepers in winter.

Garden trees continue to be a wildlife habitat even after they are dead, so leave old tree stumps in the ground where they can slowly decay. Allowing ivy to grow over them can also enhance their wildlife value.

Many beetles lay their eggs in dead branches and tree stumps and the larvae slowly tunnel their way through the decaying wood. Its nutritional value is low but these specialist feeders are adapted to slow development, often feeding for two or three years before they pupate and then hatch as adults. This plump beetle larva would be a fine meal for a great spotted woodpecker.

Great spotted woodpeckers often visit bird tables in winter - and while they are in the garden they'll sometimes take the opportunity to explore old tree stumps for beetle larvae.

Perhaps the ultimate reward for a gardener who leaves old tree stumps to rot in the garden is discovering that the endangered stag beetle has chosen to lay its eggs in it. The larvae of these spectacular beetles take four years to develop, feeding on the rotting wood. The People' Trust for Endangered Species has useful advice for gardeners who want to help conserve stag beetles - scroll down to the bottom of the page to find links to their web site.

Programme Three: Hedges

Hedges like this one, laden with flowers in summer and with hedgerow fruits in winter, have been lost from large areas of Britain. Few of us have gardens that are large enough to reproduce something as large and sprawling as this in a garden, but even formal, clipped hedges can provide breeding sites for birds and a source of food and shelter in winter for birds and insects, especially if they contain some native shrub species.

Hedges are much more than just a boundary for gardens - they are a vital source of shelter and food for many birds, especially in winter, and are often hibernation sites for insects like ladybirds. They are also the highways used by animals like hedgehogs when they move between gardens. Evergreen hedges, or hedges that retain their dead leaves in winter, like beech and hornbeam, are particularly good for providing shelter. Evergreen conifer hedges provide cover for the earliest nesting birds and always have bare ground at their base, even during heavy snowfalls, where small birds like wrens can find food. 

Informal hedges that are not closely clipped and are planted with a mixture of native species like hawthorn, guelder rose and hazel, with wild roses and honeysuckle weaving their way through them are best of all; they provide flowers, berries and nest sites. Remember that native species like hawthorn produce flowers on shoots that grew in the previous year, so if you trim all of these off when you cut the hedge in autumn you won't get any blossom or haws in the following year.

Guelder rose is a native shrub that can be a valuable addition to a wildlife garden hedge. Its flowers (above) are visited by many insects in early summer and its glossy scarlet fruits (below) are a useful resource for birds.

Hawthorn (above) is the traditional hedging plant in the countryside but it doesn't flower well if it is closely trimmed every year. To produce an annual supply of blossom and haws some shoots need to be left untrimmed each year. It also makes an attractive, small tree to incorporate in a hedge.

Even a plain, clipped beech hedge can provide a habitat for native insects. The caterpillars of this delightful little micro-moth, called a beech midget, feed inside beech leaves.

Wrens 

Wrens feed mainly on insects so fare badly in prolonged winters ........ and that's when the shelter and resources of a hedge can come to their rescue. In spring they like to sit on the hedge top and deliver their explosive bursts aof very loud song, and once they've secured a mate the males will begin to build a nest, often in ivy-covered walls.

Males build several nests and the females choose the one they like best.

The pair will usually raise about six young and when the fledglings emerge into the sunlight, dazed and confused like this individual, they can be quite approachable - but expect to be scolded by the parent birds, which are very protective of their young

Honeysuckle

The best hedges for wildlife have flowering, climbing plants like this honeysuckle trained through them. Even a uniform conifer hedge can be greatly improved by the addition of this climber which is very easy to propagate by a technique called layering. All you need to do is to pull a long, non-flowering shoot down to soil level, gently scrape some of the outer bark away from a point under the shoot about six inches behind the growing tip and then bury this exposed section of stem in a shallow layer of soil (put a flat stone on top to weigh it down) leaving the end of the shoot protruding above soil level. Keep the buried section watered and it will develop roots in a few weeks, when you can separate it from the parent plant and transplant it to a new position.

The scent of honeysuckle after dusk on warm summer evenings is intoxicating and will attract moths that come in search of nectar and will pollinate its flowers. Long-tongued bees visit the flowers during the day and some soon learn that there's an easier way to reach the nectar, instead of struggling to force their tongued down the tubular flower; instead, they crawl around the back of the flower and steal nectar through a hole that they chew in the floral tube.

Some beautiful insects breed on honeysuckle, like this 20-plume moth that's often attracted to lit windows at dusk, when you can admire its wings that are divided into feathery segments.  Each of the four wings has six 'plumes'. so it should really be called the 24-plume moth. Its larvae feed inside honeysuckle flower buds - look for the holes that they chew in them.

This is a honeysuckle sawfly, whose caterpillar feeds on honeysuckle leaves.

Blackbirds and thrushes are particularly fond of the glossy scarlet honeysuckle fruits that ripen in late summer and disperse the seeds in their droppings.

Leafcutter bees

In addition to bumblebees and honeybees, a host of other bee species will visit wildlife gardens. We have around 230 native bee species in Britain and many either excavate tunnels in the soil for their nests (mining bees) or in cavities like hollow stems.

You can give them a helping hand by providing 'bee hotels' like this old wooden box packed with hollow sections of old hogweed stems. All sorts of insects, including ladybirds, while shelter here over the winter months.

Leafcutter bees have a unique way of nesting amongst British bees, by cutting small semicircular sections from leaves (often rose leaves) and then rolling and gluing these into tubes which they lay an egg in and then provision with pollen for the hatching grub. If you find rose leaves in our hedge with semi-circular sections missing, then you know that leafcutter bees will be nesting nearby.

Leafcutter bees like to collect nectar from flowers of meadow cranesbill, which is an excellent wild flower to cultivate in a wildlife garden.

These bees don't have pollen baskets on their legs. Instead, they collect pollen on the hairy underside of their abdomen. This individual is collecting the yellow pollen of wood vetch - another excellent native plant for the wildlife garden.

When they're not feeding, leafcutter bees like to sunbathe. This one has settled on a black compost bin, which warms up quickly on sunny days.

Hedgehogs

Garden hedges are highways, used by many animals for moving between gardens. Hedgehogs roam over large territories and in summer never stay in a single garden for long, although they often return if they are fed with cat food. Their 'home patch' will be a whole row of gardens and hedgerows provide safe routes for them to commute between gardens.

Hedgehogs are assets in the garden because they eat slugs. They're most active at dusk. Sometimes they'll hibernate in large, open compost heaps or in piles of dry leaves and twigs that have been piled in a quiet, dry corner.

A hedgehog's natural defensive instinct is to roll up when threatened, presenting a ball of spines to the outside world. 

Gardens that are surrounded by continuous walls or fences are much less likely to be hedgehog-friendly. They can climb surprisingly well but small gaps in garden fences will provide them with an easy pathway on their nightly patrols in search of slugs.