How To Prepare Your Garden For A Spring Cold Snap

annuals in a greenhouse

Over the last week we’ve been blessed with glorious spring weather. Sunshine and temperatures in the high teens and twenties (ºC) have, quite literally, made the garden blossom. It’s been a delight to be outside, getting jobs done and feeling the warmth on our backs, but don’t let a mild spell lull you into a false sense of security, there’s still every chance that temperatures will plummet again. Ignored, or not properly prepared for, the result could be devastation for your precious plants. The good news is that it’s not at all difficult to protect them.

Gardeners of old would not have chanced anything to luck, keeping frost sensitive plants in a greenhouse or conservatory 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 of bringing jobs forward; we adhere less to the established rules, sometimes throwing caution to the wind. Garden centres do not help the novice gardener 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. This is shameful profiteering in my opinion. Such temptations diminish the confidence of inexperienced gardeners, who should be helped towards making good choices rather than led a merry dance.

Here in Broadstairs, by the sea, where spring is usually mild, I have often brought tender plants out into the fresh air by early April. This year is no exception. However, when a period of cold weather is forecast, I must be 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. We had planned to plant various seeds and tubers over the Easter break, but have decided to hold off for one week until it warms up. If you are lucky enough to have a heated greenhouse or a bright windowsill, then you can crack on, but we’ve used up most of our frost-safe space already. Even if your seedlings and young plants survive a cold snap their growth may be ‘checked’ (delayed) by low temperatures. You will probably find that seeds sown later overtake them, so enjoy one last day in front of the fire with a good book, or do more ground work, and save your seeds for another day. Even hardy plants 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 safe 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 or greenhouse until the chill lifts. 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 during the day, especially if it’s warm. It does not 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 bring plants back outside during the day if you have the time and energy to do so.
  3. Cover everything else. Cold snaps 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. Take the greatest care, as covering clumsily can do more harm than good. It is rarely wise to dig a treasured plant up in such circumstances: cloches can be used to protect larger and more delicate plants. 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 underneath; slugs and snails may also move in and give you a different headache altogether. Where tender plants are yet to break the surface of the soil, for example dahlias, gingers, gladioli and cannas, a good, thick mulch will help to 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. Broadstairs is awash with the most gorgeous magnolia and camellia blossom at the moment. It’s magical to behold. Sadly, if the temperature drops below freezing the blooms will 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 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 measures are simply a sensible precaution and a small price to pay for keeping your garden on track for the year. 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. TFG.

Trays of annuals in an unheated greenhouse can be covered lightly with fleece or newspaper on frosty nights.