I was looking, if truth be told, for any product that would definitely eliminate liverwort, that curse of the modern gardener and all-too-often available … entirely free of charge … with container-grown shrubs in many a garden centre. This latter facility helps to explain why I was browsing in several local garden centres during my quest, for I am pretty sure that most garden centres would have banished liverwort from their pots and their premises were the task as simple as sprinkling on, spraying on or brushing on a readily-available product. Be that as it may, all the garden centres I visited were ablaze with beautiful bedding plants in flower, bright and cheerful and very tempting. And, although there were usually signs somewhere with the cautionary words, “protect from frost,” all too many customers were happily filling their trolleys with boxes of these lovely plants. I was tempted, I will admit: but reality reasserted itself and I was able to order Satan to stop pestering me. “These plants are in flower rather than in bud,” I told Old Nick, “and these plants will die if they are exposed to frost. No, no, no, it is too soon to plant these out in a garden in east-central Scotland.”
On Saturday morning I looked out at my garden; and I was not surprised to see that the bird bath had a goodly layer of ice … not a mere skimming … which would have borne the weight of virtually any species of garden bird. And I wondered how many of the garden centres’ customers would, within a few days, realise that their not-inexpensive bedding plants had shuffled off this mortal coil and would be blaming themselves … the right people to blame … for the wrong reason. I wish I had a pound for every time I have heard someone say, “Bedding plants don’t do well for me; I just don’t have ‘green fingers.’ No, it’s not a lack of ‘green fingers’; it’s a failure to follow advice which is the problem.
So when is it safe to expose tender plants to the rigours of our climate in and around Falkirk? Is there a calendar date … like Christmas Day or May Day … when we can reckon that all risk of frost has passed? And, gentle reader, I think that you already know that there is not. About the best that can be said is that one can get general guidance of what might be termed the ‘last frost date’: but that is by no means a guarantee that frosts will not came after that date. And notice that the best word is ‘frosts’ … the plural form of frost … for there is air frost and ground frost, the difference being explained by the Meteorological Office (the Met Office) in these words. “ An ‘air frost’ occurs when the temperature at 1.25 metres above the ground falls below 0 °C, whereas incidence of a ‘ground frost’ refers to a temperature below 0 °C measured on a grass surface.”
The Met Office also offers the gardener the benefit of their many years of record-keeping with this alarming statistic. “The average number of days with air frost in Eastern Scotland varies from less than 40 a year on the coast of Fife to more than 90 a year over the higher ground of the Lammermuir Hills and Grampians. Ground frost averages range from less than 90 to over 150 days per year, with a similar distribution to air frost.” So, in Polmont, I’ll be very lucky to have fewer than 50 nights with air frost and 100 with ground frost even in a good year! And the statistics reveal that I can expect 13 nights with ground frost in an average April and 6 in an average May. Even a typical June will produce one night when it’s frosty. The answer is now pretty clear; don’t put tender plants into the garden before late May in central Scotland unless you can protect them with cloches or fleece, and even then don’t be astonished if the most exposed suffer from a touch of frost. B-r-r-r ... it’s f-freezing!