Nature Notes Nature Photography Corner: Evergreens

As Spring starts to creep in and the first bud bursts appear, it's easy to overlook the trees and plants that have stayed green and lush all through the winter, the evergreens. The four most common ones can be seen in gardens and local parks and are all important for wildlife.

In Railway Fields, the most obvious evergreen that covers much of the ground and climbs up the trees is ivy. Ivy is often unfairly maligned as a tree strangler but it is actually a highly valuable plant to wildlife.

The leaves are dark green and glossy with pale veins. The leaves of juvenile forms have 3-5 lobes and a pale underside. On mature forms, leaves are oval or heart shaped without lobes.

The nectar, pollen and berries of ivy are an essential food source for insects and birds during autumn and winter when little else is about. It also provides shelter for insects, birds, bats and other small mammals. The high fat content of the berries (pictured below) is a nutritious food resource for birds and the berries are eaten by a range of species including thrushes, blackcaps, wood pigeons and blackbirds.

Ivy is particularly important to many insects before they go into hibernation. Some of the main insect species which forage on the nectar and pollen of ivy are bees, hoverflies and common wasps.

It is also an important food plant for some butterfly and moth larvae such as holly blue, small dusty wave, angle shades and swallow-tailed moth.

Many rare insects are attracted to ivy flowers, including the golden hoverfly.

Another common evergreen that is dotted around the site is Holly. 

Like ivy, the leaves vary according to the age of the plant. The leaves of the young plant are spiky, dark green, glossy and oval, but the leaves of older trees and in the upper parts of the tree are much more likely to be smooth. 

Holly provides dense cover and good nesting opportunities for birds, while its deep, dry leaf litter may be used by hedgehogs and small mammals for hibernation.

The flowers provide nectar and pollen for bees and other pollinating insects. The leaves are eaten by caterpillars of the holly blue butterfly which are very common at Railway Fields, along with those of various moths, including the yellow-barred brindle, double-striped pug and the holly tortrix.

The scarlet berries are a vital source of food for birds in winter, and small mammals, such as wood mice and dormice. If a mistle thrush is in the vicinity it will guard a berry laden tree fiercely. The berries on that tree won’t be eaten, but will be guarded with such care that no other birds can take them either. Mistle thrushes are so good at protecting their trees, just in case, that by spring many will still have their full crop of berries untouched, long after any unprotected holly has had its fruit stripped. This tree in Downhills Park was laden with rich berries.

The tree to treat with some respect in the woodland is the yew tree with its straight, small needles with a pointed tip, coloured dark green above and green-grey below. They grow in two rows on either side of each twig.

Yew flowers will be beginning to show themselves next month. Yew is dioecious, meaning that male and female flowers grow on separate trees and are visible in March and April. Male flowers are insignificant white-yellow globe-like structures. Female flowers are bud-like and scaly, and green when young but becoming brown and acorn-like with age.

The yew is a conifer but unlike many other conifers, the common yew does not actually bear its seeds in a cone. Instead, each seed is enclosed in a red, fleshy, berry-like structure known as an aril which is open at the tip. The seeds are highly toxic (indeed all parts of the tree are poisonous and should not be burned or left where animals could eat it) but birds like to eat the red flesh on the outside which is not poisonous to them. Despite its poisonous nature, anti-cancer compounds are harvested from the foliage of Taxus baccata and used in modern medicine.

The mythology of the yew tree is extensive and would constitute a post all to itself but yew trees are associated with churchyards and there are at least 500 churchyards in England which contain yew trees older than the buildings themselves. A beautiful ancient yew that is over 1,000 years old can be seen in Totteridge in St Andrew's churchyard. The biggest yew you can see in Railway Fields is in front of the cabin. Sometimes tiny goldcrests can be seen in it but more often than not you'll spot a resident robin hopping around it.

The fourth evergreen tree you can spot easily in Railway Fields is the non-native Holm Oak. It was introduced from the Eastern Mediterranean to Britain in the late 1500s and is now naturalised in this country. Although not as valuable to wildlife as native English and sessile oaks, its catkins provide a source of pollen for bees and other insects, and its dense, evergreen canopy offers year-round shelter for birds. 

The leaves are oval, dark green to black and concave with a coating of pale hairs on the underside. Young leaves are spiny, like holly leaves, whereas older leaves have smooth edges.  Like the yew tree, the holm oak is viewed by many to be a sacred tree, and they were planted in the Mediterranean in sacred places to keep away evil spirits. The ancient Greeks used the leaves to tell the future. 

As you walk around the local green spaces this Spring as well as admiring the daffodils, primroses and other bright coloured blooms and blossoms, also keep a look out for yew flowers, holm oak catkins and the black berries of the yew that are still nourishing the local bird life.  Evergreens are often overlooked as they are just...well..there but they can be just as fascinating to examine as their deciduous cousins.

Share your pictures of the evergreens in your neighbourhood. You might spot cotoneasters, cypresses, conifers, pines, olive trees, box and on the shady bottom path at Railway Fields an example of a rather handsome tree which is rapidly naturalising itself in Railway Fields, probably as a garden escapee, the loquat.