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Tuesday 19 June 2018

Protecting your plants for winter

By Andrew Collyer - Practical Gardening

Ghostly frost protection at Blarney Castle.
Ghostly frost protection at Blarney Castle.

Clear out greenhouses of finished tomato plants

Corylus avellana 'Contorta' [ corkscrew hazel]

In general our climate is pretty benign and this allows us to grow plants in Ireland that are really frost tender and do so sucessfully with the caveat, most of the time. We do this to a point of taking these plants for granted assuming they need no special winter treatment or protection.

Agapanthus, Hebes, Griselinia, Ceanothus, Phormiums, Crinodendrons are garden mainstays in Ireland all of which are not totally hardy as I found out in the frosts of the 2010 and 11 winters when all these plants suffered in my garden. These plants can be considered tough compared to some plants we grow. Coronilla, Abutilons, Acacias, Dahlias left in the soil all winter, bedding Geraniums and Marguerites left outside to over winter, tree ferns and even bananas. I even have a customer who is growing a beautiful plant called Tibouchina urvilleana known as the Princess Flower, a native of Brazil, and really should be considered a conservatory plant. It's outside in a mild sheltered coastal garden and has no additional protection other than its protected site and while it does get knocked around a little in winter it has survived three years. However, while it is fun trying to grow tender plants like this outside whether protected or not, ultimately it is only for the keen plants person and one that will not mourn a tender plants loss too much when the inevitable happens.

This weather pattern of generally mild winter conditions but with spikes of cold can prove a challenge when it comes to providing frost protection for plants purely on the basis of missing a forecast or being away for a week and not being ready or available to cover up. In countries that have solid cold from say November to March you can safely wrap up plants and leave them in that state for the duration. In Ireland it is much more likely you will, especially with evergreens, wrap and unwrap as the temperatures dictates.

Being prepared to protect your tender plants is the key to their survival. This includes taking note of the weather forecasts but also having a suitable covering material available to wrap or cover your plants with. You can buy a product called horticultural fleece which is a light transparent woven material that allows a certain amount of light to penertrate through to the plant while affording a certain amount of protection from frost, snow, hail and wind. This product comes in different grades of thickness ranging from 17g per square metre to 35g. The heavier the grade the better the frost protection but the transparency levels are reduced. Theses fleeces can keep off between 3 to 7 degrees of frost, you can double up to provide higher thermal qualities.

Because we rarely permanently wrap our plants for all of the winter opaque materials can also be used for short period, old heavy sheets, blankets and towels are all suitable for this short term use. In 2010 I used two large blankets to throw over a mature olive tree when a minus eight to ten degree frost was forecast. I tied it down with ropes and left it in place for around a week until the cold spell was over. Whether it saved this valuable plant from death I'll never know but it certainly saved it from substantial damage.

Plastic sheeting can also be used but it is important that a frame work is constructed to keep it from contacting with the plant it is protecting, this is like creating a mini polytunnel around the plant. Plastic touching a plant surface in frosty weather can cause serious burning damage. Mulches are an effective way of protecting herbaceous plants from frost. A 75mm layer of manure or compost over the crown of Agapanthus, Canna lilies, Watsonias and Dahlias will not only provide a safety barrier but also imporove the soil conditions around them.

In reality the vast majority of the plants you have in your garden will go through the winter largely unscathed if the temperatures are what we would consider normal for the time of year but it doesn't hurt to be prepared for the unexpected.

Wexford People