Tuesday 23 January 2018

Gardening with Diarmuid Gavin - protect your plants

Plunging winter temperatures can leave plants withered and black, so take some simple steps to keep them safe 'til spring

Frost is a danger in the garden
Frost is a danger in the garden
Homemade garden cloche

Diarmuid Gavin

One of the joys of gardening in Ireland is our temperate climate; our lack of extremes of hot and cold, or wet and dry. This combined with being an island - the sea acts as an effective hot water bottle for many areas of the country - allows us to cultivate many ornamental plants and agricultural crops which have originated in warmer climates.

It really is quite extraordinary that we are able to grow a vast quantity of plants from Asia, the Americas and even Australia. It also means that, as a nation, we have been at the forefront of gathering plants from around the globe to add interest and colour to our gardens. Even species which seem at home here - geraniums, fuchsia, begonias, dahlias - originate in much warmer climates.

If we relied only on plants native to our group of islands, our gardens would look quite different - and at some times of the year, almost destitute.

What other foreign species have made their homes here? Well, if we examine some of the most popular plants in our gardens we see that lavender arrived from the Mediterranean, roses from Asia and, of course, potatoes from South America.

The wisteria which is winding its way up my house is from China and Japan, hydrangea from Asia, our cottage garden lupins came from North America and bamboo from eastern continents. This brief list forms the backbone of many of our planting styles. And most of these species thrive here because they are relatively hardy, meaning they will survive our average winters.

In recent years, however, we have had winters that saw more extreme weather conditions - with plunging temperatures and high winds. Most gardeners across the country will have learned the hard way that if plants are to survive and thrive in these conditions, they will need winter protection. And now is the time to do it.

Freezing temperatures are damaging to plants because most of a plant is made up of water, and when water freezes it expands. When this happens within a plant cell, it breaks down the cell walls which causes the plant to wither and blacken. As well as this, when the ground becomes frozen it can be difficult for even hardy plants to obtain moisture through their roots.

The simplest method of protecting your plants this winter is to bring them indoors into a greenhouse or mildly heated conservatory. Even placing them in an open verandah or close to the eaves of the house will provide some protection. Some tender plants such as cannas, gladioli and dahlias will be dormant in the winter and can be lifted for overwintering. You can also take cuttings of tender plants to ensure new stock for next spring.

If you can't bring plants indoors, some can be protected in situ. Mulching around the base will help any plant survive the winter. This can be achieved with straw, bark mulch, dead leaves or compost. You could also cover tender plants with horticultural fleece or perforated polythene.

Individual smaller species can be protected with their own cloches, and larger species can be wrapped in Hessian or even bubble wrap. Tree ferns will benefit from their trunks being covered but also their crowns where new growth emerges. Other at-risk plants include bananas, bay trees, cordylines, palms, echiums, pittosporum and mimosa (acacia dealbata).

It's not just the plants that can be tender - clay pots can crack over the winter too, so wrap up any that are not frost-resistant in Hessian or bring them inside.

We are being told to expect a snowy winter this year. Funnily enough, snow is not particularly damaging to gardens and can even act as an insulator against extreme temperatures for plants. However, its weight can cause branches to snap and hedges to splay, so if it's possible to get out into the garden after a snowfall, remove as much snow as possible from vulnerable branches and the tops of shrubs.

In parts of Japan that are hit every year by heavy snowfalls, nature lovers build maypole-like structures - a central stem of thick bamboo from which strands of bamboo rope splay out and are tied around the limbs of old pine trees - to take the weight of snow-laden branches. While you wouldn't do something as elaborate here, you could consider tying in column-shaped conifers so they won't lose their shape.

To help your garden survive through to spring, keep a watch on the weather forecast and be ready to dash out and do the necessary before we wake up in a winter wonderland!

This week in the garden:

It’s a good time to go out and do a bit of pruning. Inspect trees and shrubs for dead or diseased branches and remove. Remember to leave acers and birches until mid-winter as any other time they can bleed sap.

Time to put the borders to bed for winter: dig up weeds and give a good cover of mulch or compost. Tender plants like salvias need to be dug up, potted and put in a frost-free conservatory for the winter.

Start a compost heap if you haven’t got one, it’s a great place to dump cold wood ash from the fire.

Lift and store veg such as carrots, potatoes and beetroot. Leeks and parsnip can remain in the ground longer.

If you are forcing bulbs for Christmas, take a peek at them now and see if they are ready to be brought indoors. This is when the root system has developed and they are showing about 2in of  green growth. Keep them somewhere cool initially and away from bright light.

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