Frost and your plants...... are you a chancer?


Do you remember a time when you picked up a pretty plant in the garden centre to have a look at its label, only to discover it was marked as not completely frost hardy? The label may have said to plant it in a protective environment, but some gardeners tend to plough ahead and chance positioning their tender specimen outdoors. Result, well over the last week or so whilst its owner sweated indoors, poor Pete the palm tree shivered outdoors, hoping and praying for the cold spell to end.

Let's be honest, we've all done it. Like many other gardeners before me I was lulled into a false sense of security by the last couple of "soft" winters, assuring myself that I would never again see a harsh sustained frost. I planted a few exotics outdoors and now I am worried as I wait for the frost to retreat.

Exotic plants are just that, exotic, unusual, and great talking points. But beautiful as they may look, they may not survive one of our occasionally hard frosts. This is one weather element that is regarded as exotic in their native homes.

Hardiness zones.

To avoid such calamities it helps to know a bit about hardiness zones. A hardiness zone is a geographically defined area in which a specific category of plant life is capable of growing. A plants rating for growing in a certain zone is directly related to its ability to withstand the minimum temperatures of that zone. The zones are as follows....

Zone 2: -46 to -40 C (-50 to -40 F)
Zone 3: -40 to -34 C (-40 to -30 F)
Zone 4: -34 to -29 C (-30 to -20 F)
Zone 5: -29 to -23 C (-20 to -10 F)
Zone 6: -23 to -18 C (-10 to 0 F)
Zone 7: -18 to -12 C (0 to 10 F)
Zone 8: -12 to -7 C (10 to 20 F)
Zone 9: -7 to -1 C (20 to 30 F)
Zone 10: -1 to 4 C (30 to 40 F)
Zone 11: above 4 C (above 40 F)

Due to the moderating effect of the Gulf Stream on our Irish temperate maritime climate, we receive rather milder winters than our northerly position suggests. Fewer extremes of temperature can occur when a site is located on an island or near a large body of water, which is usually good news for us. This means that the hardiness zones relevant to Ireland are quite high, from 7 to 10.

Where possible, check the labels in the garden centre, do your research, ask local gardeners, and choose frost-hardy varieties for planting in your garden. If a plant label says "hardy down to zone 6 then you know it will take temperatures down to at least -23 to -18 C to begin to do it harm.

Frost protection.

You should always have a few things to hand to offer protection to your plants. Basically, anything that prevents frosty air coming into contact with the plants leaves and stems is of benefit.

Sheets of newspaper weighed down with stones, large plastic bottles with their bases removed, and old pots are all suitable for covering smaller plants. For larger plants and trees, old sheets and light blankets, again weighed down with stones will offer frost coverage from top to bottom. Instead of weighing them down, many gardeners instead clip the covers around their plants using clothes pegs.

It's worth remembering that these covering materials block light, so they should be removed the next morning, allowing both sunlight and heat to reach the plants. For longer freezes, and day freezes, garden fleece or frost cloth may be more suitable. This is a specially designed material available through garden centres, offering frost protection but allowing lots of light in to the plant, so it can be left on the plant longer.

Here's hoping for a levelling off of the temperatures to allow our tender plants some much needed respite. Until next week, happy gardening and remember that a weed is just a plant in the wrong place.

View further information on this topic in the Irish gardeners forum >>>>

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