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Preparing Your Garden For A Cold Snap

Preparing Your Garden For A Cold Snap

It’s spring and the weather is fine. Sunshine and temperatures in the high teens and early twenties have encouraged our gardens to burst into life. It’s a delight to be outside, feeling the warmth of the sun on our faces. It’s a moment to savour, but we must exercise caution as there’s still every chance that temperatures could plummet again. Not properly prepared for, the result could spell devastation for our precious plants. The good news is that it’s not at all difficult to avoid catastrophe.

Gardeners of old would not have left anything to luck, keeping frost-sensitive plants in a heated greenhouse or protected by cold frames until the end of May or early June when all chance of frost had passed. These days climate change has tended to make us a lot more confident in planting things out earlier and fewer of us have the benefit of growing under glass, relying on overcrowded windowsills instead. Garden centres encourage us by offering tender plants such as half-hardy annuals extremely early in the year when they still require one or two months indoors before planting out. If you don’t have a greenhouse or conservatory, don’t be tempted into buying too soon and save yourself the money and heartache.

I live by the sea where winters and springs are often mild and frost-free. I have occasionally brought tender plants outside by early April so that they can benefit from the same fresh air and sunshine that does me good. However, when a period of cold weather is forecast, I am on standby to put my plans into reverse. Here are some of my top tips for surviving a spring cold snap with your garden unscathed.

  1. Delay sowing and planting. By March, gardeners have a strong urge to start doing something. While it’s true that many flower and vegetable seeds can be sown early in the season, in most cases it makes very little difference if you hold back until mid or late April when the weather is warmer. Longer days mean that newly-germinated seedlings soon accelerate away. Even if your seedlings and young plants survive a cold snap their growth may be ‘checked’ (delayed) and so you’ll have gained very little. Trees and shrubs that have started into growth are more susceptible to frost damage now than they were over winter. Newly formed tissue is considerably more vulnerable than overwintering branches, crowns, tubers, roots, rhizomes etc., especially when exposed to the elements. By and large, spring bulbs, hardy annuals and biennials are completely unphased if temperatures dip below freezing for a short time. They are used to such conditions and will bounce back immediately it warms up again.
  2. Move what you can. If you have vulnerable plants that can be moved, for example growing in pots, pop them in a garage, shed, porch, greenhouse or spare bedroom until the chill abates. Even if the space is unheated, it’s unlikely a spring frost will be heavy enough to permeate that far. Keep plants off the floor where the air is coldest and out of draughts if at all possible. Ventilate your holding space during the day, especially if it’s warm. It does not usually matter if plants are left in the dark for a couple of days. Better that than frosted. The critical period for frost is 8pm to 8am, so you can put plants back outside during the day if you have the time and energy to do so.
  3. Cover everything else. Cold snaps in spring don’t generally last long, so use anything you have to hand to protect plants in situ. Horticultural fleece is ideal for wrapping larger plants or laying over emerging seedlings in trays, pots or raised beds. If you don’t have fleece to hand, you can use old sheets or blankets, bubble wrap, bin liners, cardboard boxes or newspaper. Be careful not to crush or damage any fragile new growth but do anchor your coverings, especially if wind is forecast. Garden canes with old tennis balls skewered onto the ends are great for supporting fleece, sheets and netting. Take the greatest care, as covering plants clumsily can do more harm than good. Cloches can be used to protect vegetables such as early potatoes and perennials such as salvias. If you don’t have cloches, upturned buckets or pots with the drainage holes bunged up will do just fine. Remove them as soon as you possibly can, otherwise the plants will become drawn and leggy. Where tender plants are yet to break through the surface of the soil, for example dahlias, gingers, gladioli and cannas, a good, thick mulch will help protect them in the short term and nourish them in the long term.
  4. Accept that nature is in charge. In some cases there is very little you can do to protect plants, especially large ones. Our gardens will be awash with blossom in April - it’s magical to behold. Sadly, if the temperature drops below freezing the blooms may be scorched and rendered brown and unlovely. This will be heartbreaking, but it’s a risk one takes: for every year when disaster strikes there will be five or six when it does not. The trees themselves will not be harmed and will go on to bloom beautifully again. The impact of frost on fruit tree blossom has a longer-lasting effect, potentially destroying the year’s crop. If you have small fruit trees that can be wrapped in fleece, try that. If you live somewhere that’s susceptible to spring frosts, seek advice on varieties that blossom later.
  5. Avoid treading on your lawn. The crunch of frosted grass underfoot may be enjoyable, but your lawn will not share your amusement, especially if it’s actively growing again. With each footstep, you are breaking hundreds of frozen blades of grass. This in turn ruptures new tissue and causes it to die back. Wait an hour or two until the sun has melted the frost and then stride forth on your daily garden inspection. Your lawn will thank you for your patience. 

A spring cold snap is unlikely to last for long. Most protective measures are simply a sensible precaution and a small price to pay for keeping your garden on track for the year ahead. If the worst happens and seedlings or plants are lost to Jack Frost, there is still ample time to resow, replant and generally catch up. Long-lasting damage as a result of a spring cold is unusual, unless the plants concerned are very tender, in which case they could be killed outright. Avoid that situation by being patient, studying the weather forecast and erring on the side of caution. If ever there was a parallel with Aesop’s fable ‘The Tortoise and The Hare’, it is this. Slow and steady wins the race.

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