I’ve had carrots and rocket and a few herbs growing in big pots by the back door. I’ve been watching them over the last couple of months. A hearty germination, then spindly growth, a full on spurt in still-warm autumn, when it finally rained. Over the last couple of weeks we’ve had some cracking frosts and cold days. Every morning, there they are, absolutely wilted and iced over, by mid-day looking perky and upright again, until the cold sets in again. Add to that short days and long nights and it’s a wonder anything can grow or produce at this time of the year; limited light, limited warmth, slowed metabolism, and the added daily battering of frosts!
It’s not the actual frost that does most of the damage, it’s the thawing. When plants are frosted, the water in their cells freezes. If it thaws out too quickly, the cell walls can rupture, causing cell death, withering, blackening and ultimately plant death.
Newstead is reknowned for frosts and it is one factor that influences gardening here. We mostly get radiation frosts where an inversion layer traps the cold air below the warmer layers – cold air is heavier, so it tends to sit in a layer at the ground surface and flow, like water, to the lowest points in the landscape (one reason why Maldon is far less frost-prone).
There are a few factors that influence frost, there are ways to slightly mitigate it, and there are plants that love and loathe the cold. Artichokes, beets, carrots, cauliflower, celery, chinese cabbage, endive, lettuce, parsnips, peas, swiss chard, escarole, arugula, bok choy, mache, and radicchio can withstand light frost. Broccoli, Brussels sprouts, cabbage, collards, kale, kohlrabi, mustard, onions, parsley, peas, radishes, spinach, turnips, leeks, and sorrel are good in heavy frosts, although pea flowers – and in fact most flowers – are frost tender.
Dry soils tend to accentuate frosts – a moist soil can hold up to four times more heat than dry soils and is a better heat conductor. Clay and loam soils hold heat better than sandy soils. Dark soils are better than light. Some straw mulches can accentuate frosts as they create greater temperature differences at the soil surface.
Humidity, air flow/movement and moisture can all reduce frost impact, so irrigating the soil the evening before a frost, or spraying plants during frost can help. Creating local microclimates by using walls or north facing sites, protective plants or trees, painting dark trunks of fruit trees with whitewash, providing frost covering – floating row covers, or frost cloth, or even a bed sheet or lace curtain- are some other ideas.
So, enough on the cold, it’s still good weather for gardening and the July Notes have been posted to guide you. And if all you get achieved next month is to study seed catalogues and perhaps order some bare root plants, whilst sitting in front of the fire with a hot drink, I’d say that’s a productive way to spend winter!
NB. Brian Keats says that Sunday 6th July will be the aphelion – when the earth and sun are furthest (152.1million km) apart. After that they start moving slowly towards each other for the next six months and Brian says this change in rhythm will lead to turbulent weather and cold gusts from the south pole.