Over the course of the past couple of weeks, Jack Frost has paid a couple of visits to the garden, decorating everything with a fine dusting of ice crystals. From the mild, dry and sunny days of early autumn, we have moved into a colder and wetter phase of the year. Last week we reached the milestone of the first frosty morning since the spring.
The short, sharp, shock of a cold and frosty morning can initially be exciting and invigorating. This soon gives way as the cold begins to penetrate and chill the bodies extremities. I quickly realise that like the squirrel, busy collecting and storing his nuts for the winter, I must set about my tasks with urgency, if only to keep the blood flowing and my feet and fingers from frostbite.
Frost will form on surfaces when they have been chilled below 0c. The water moisture in the air condenses on the surface and freezes to form ice crystals. The extent of this chilling, the moisture content of the air and the speed at which the moisture condenses all effect the eventual appearance of the frost. A ‘hoar frost’ occurs in a moist atmosphere when a surface has been quickly chilled to several degrees below freezing, and refers to the way everything appears to be coated with a thin layer of white hairs.
This severe drop in temperature signals the end of the road for the tender, frost-sensitive plants. Their leaves will blacken and wither, quickly turning to a slimy mush when the frost lifts later in the day. It is time to move the summer annuals to the compost heap and lift the dahlia tubers so they can spend the winter somewhere slightly warmer.
For more tender plants like bananas, we have hopefully managed to pre-empt the arrival of the cold weather, and they are now wrapped up cosy inside layers of straw, hessian or fleece, gently slumbering until the return of the spring rouses them once again.
For some plants, this colder weather will bring out their best. For roots like carrots or parsnips, and brassicas like cabbage or Brussels sprouts, the cold weather will prompt them to turn the starch in their cells into sugar. The increased concentration of sugars in the plants fluids lowers their freezing point, acting like a simple ‘anti-freeze’ solution, but also greatly improving their flavour.
Many of our native tree seeds need a period of cold weather followed by warmer temperature, known as stratification, to grow. This process of freezing and thawing breaks dormancy of the seed and kickstarts the process of germination.
Whilst it is damaging for some plants, a period of hard frost can be good for others. The cold may help to reduce populations of some fungi, bacteria, viruses and insects that need living material to continue their lifecycle.
The trees are now shedding their summer coat of leaves, and before long they will once again be bare. There is a unique beauty to the stark reality that this part of the year presents us with. It isn’t often that we have the opportunity to see the bare skeleton of the garden, stripped of all its summer decoration. It is a chance to see the structure of every tree and shrub. A chance to make plans, plant bulbs and order seeds to fill the bare spaces next year. The pace of work in the garden changes and I find I now have time to spend focused on just one area. I know that every hour I can spend working on the garden now, will repay itself tenfold next year, when I will once again be overwhelmed by the pace of spring and summer as they hurtle by.
If it were not for the cold days, I know that I would certainly not appreciate the warmer days as much when they finally do return.