There are so many wonderful things happening in the garden at this time of year. The long awaited bulbs planted in autumn have finally emerged, the birds are nesting, the earthworms are squirming into action, and the days are becoming well and truly longer.
This time of the year brings so many temptations for British gardeners to get outside and throw everything into the ground. We are experiencing more frequent warm and sunny stretches in the weather (kudos, global warming) which lull even the most experienced gardener into a false sense of security. But one little cold snap can really put all your springtime hard work to the test.
Earlier in the season, I sowed some dwarf annual dahlias – distinguished in that they are quickly grown from seed rather than the more robust and ever-so-slightly hardier tuber variety. We took advantage of the last couple of warm and sunny weeks in the UK to test a few of them out in the ground at our home garden and in a pot on the allotment – and boy, did that experiment go badly!
The unpredictable and easily temperamental springtime weather struck last night. After days of glorious sunshine and highs of 19 degrees (65F), we had a sharp cold snap. This morning we woke to -1 degrees (30F) and a thick layer of frost. The dahlias really got the worst of it.
RIP, little guys.
So, what actually happened to these plants that did not effect the surrounding lupins, geums, and geraniums? The simplest (and shortest) answer is that these are young, rather than established, plants which are more susceptible to frost. But more accurately, what happened after the frost is just as much to blame.
When a young, tender plant is exposed to a sharp decrease in temperatures and a subsequent frost, the delicate cells inside the plant freeze. Although it was below freezing this morning, it quickly turned into a bright, sunny, and warm day – well, warm for northern England. This extreme change of temperatures in such a short period of time caused these frozen cells to expand too quickly and burst. It’s the same principle behind why a boiling hot water glass will shatter when exposed immediately to ice.
Unfortunately, this is just one of the many realities of springtime. Fortunately, there are ways that you can avoid this same mistake.
- Cover tender plants with protective fleece or some sort of cloche made with breathable fabric. An old thick bed sheet or a bath towel would work just as well and doesn’t require a trip to the store.
- Move all cold sensitive plants inside, if possible. This is a really good idea for those that are in terracotta pots as they can become extremely cold.
- For younger plants already in the ground, cover with a mini polytunnel (if you have it) or something similar. If you don’t have this, take an empty 2 litre soda bottle, cut off the bottom, and place upright over the plant. This will act as a mini insulator and serves the same function as a greenhouse or cold frame.
- Resist the urge to plant out tender annuals until the risk of frost has completely passed. No matter how much you have hardened it off – like we did – few newly sown summer plants can survive the unpredictable cold snaps of a British spring.
There is always a chance that these plants will recover with a bit of warmer weather and, thankfully, the forecast for this week looks pretty promising. We don’t have the highest of expectations, but in these uncertain times you look for hope wherever you can find it.
Stay safe out there, little plants. You too, folks.
Dig for Goodness Sake 
Do you have irrigation or do you water by hand? If you have irrigation, running it through the night on known evenings of a frost will actually keep your plants warmer. The constant application of earth temperatures will prevent frost from forming. This is something I do in Florida, where even our coldest nights produce at least 65F sunny days, so rot or blight may be a concern where you are if the days are also cold and wet. But something to consider. Thank you for the informative post! Hugs from across the pond!
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