We can all do our bit for the environment by planting a tree, and the variety of trees means there is one to suit any kind of garden, writes Ros Drinkwater.

Driving into Newtownmountkennedy en route to Diana Scarth’s plant sale I passed an extraordinary complex of green timber buildings that put me in mind of Hansel and Gretel.

Curiosity being my middle name I turned around, drove back and parked in the visitors’ bay. In reception a young woman informed me that this was the headquarters of Coillte Teoranta, the state forestry company that manages over a million acres of forest.

That may sound like quite a bundle of timber, but it accounts for only 10 per cent of our landscape compared to the European average of 36 per cent. Coillte’s current plan is to increase this to 17 per cent by 2035 by planting 20,000 hectares of forest every year.

The oldest living organisms on earth, trees are essential to the planet’s wellbeing as they capture more carbon from the air than anything else, convert much of it into wood and through photosynthesis release oxygen back into the air, thus helping in the battle against global warming.

In the grand scheme of things planting a tree in your garden amounts to no more than a drop in the ocean, but what else is an ocean made up of but drops?

Aesthetics apart, a tree’s biggest plus is that once it is established it pretty much takes care of itself. The first thing to decide is what role you intend it to play. There are species for screens, evergreen native Irish holly and arbutus, deciduous maples, hawthorns and beech, which will keep its leaves if trained as a hedge.

Those that create shade and shelter include laburnum and magnolia, both with fabulous flowers.

For colourful foliage, acers run the gamut from lemon yellow to deep crimson. For fruits think of apples, pears, damsons, cherries and plums.

The Rowan tree will attract bees and butterflies and its colourful berries provide a banquet for birds. There are trees with beautiful barks such as snakebark maples and birches, and species that will thrive in containers, hollies, bay laurel and dwarf conifers.

Last, but by no means least, there are feature trees intended as the principal focal point of the garden.

For an overview of the possibilities I would recommend a visit to the National Garden Exhibition Centre in Kilquade, Co Wicklow where 20 gardens showcase virtually every species suitable for an Irish garden, large or small. Should you have room for only one feature tree, an evergreen might be a wise choice.

In the Water and Rock Garden you’ll find my favourite, Abies koreana, conical in shape, its branches bristling with fat, violet cones. When I bought my own at the exhibition centre five years ago, it fitted neatly on the back seat of my car. Today it is a four metre tall beauty.

Still with specimen trees, the Water and Woodland Garden features the spectacular Cornus controversa Variegata, commonly known as the wedding cake tree because of its habit of growing branches in tiers.

In maturity this can grow over eight metres tall and eight metres wide, so it’s a tree strictly for the large garden.

A smaller alternative would be Cornus alternifolia ‘Argentea’ Variegata, also known as the Pagoda Tree, which you will find in the Oriental Reflections Garden. It has the same tiered branch habit, but will grow only three metres tall.

Before your visit try to determine what kind of soil you have, acid, neutral or alkaline.

In a recent TV gardening programme John Cushnie gave a thumbs down to cheap soil testing kits and suggested the easiest way to determine your soil type is look over the fence and see what the neighbours are growing.

An abundance of heathers, rhododendrons and blue hydrangeas indicates acid soil. Ceanothus, Persian lilac and Buddleja signal alkaline. This method should not be regarded as foolproof.

I have a pale blue hydrangea, but it only stays that way because I dug a hole five foot wide, five foot deep and filled it with ericaceous soil which I top up every year.

I’ll finish with a footnote from history. Did you know that Ogham, the original Irish alphabet, derived from tree names? It began with eight letters, Scots pine (a), birch (b), hazel (c), oak (d), alder (f), yew (i), ash (n), and willow (s). Medieval scholars added 12 more, by which time they ran out of trees and turned to shrubs to complete the alphabet, ivy (g), bramble (m), reed (Ng), gorse (o) and heather (u).

National Garden Exhibition Centre, Kilquade, Co Wicklow; tel 01-281989; www.gardenexhibition.ie