How to help frost damaged plants

This spring seems to have been one of the most unpredictable for gardeners, as far as the weather goes, for many years and has resulted in some plants being damaged by frost. And after all those frosty nights and even snow, it looks as though May will be cool thanks to the soil not having warmed up. The key thing is not to panic!

For me, like other gardeners, such changes from mild south-westerlies to an arctic northerly blast are frustrating. Just as my magnolia was in full flower, the frosty nights turned the beautiful blooms from pure white to teabag brown and the new shoots on many other plants have been caught in the same way.

Why have buds turned brown on plants

But it’s not just the cold that’s causing the problems. The drying wind from the east, coupled with little in the form of rainfall in some parts of the country, means that newly emerging buds and the foliage on evergreens is being scorched too. In my garden the buds on Hydrangea villosa were shrivelled after they were coaxed into growth by a week of warm weather and then frazzled by a week of easterly winds and overnight frosts.

And an enthusiastic Cercidiphyllum japonicum suffered the same fate too, although not all the baby leaves were affected. Fortunately the hardy shrubs and border plants are tough enough to cope with the onslaught and though a few buds may have been killed, you’ll find they regrow happily once we return to warmer weather.

Protecting less hardy plants outdoors

Other garden plants that are of borderline hardness outdoors, and which would have sailed through last spring, have undoubtedly taken a bit of a pounding in gardens all over the country. I grow lots of exotic looking species in the sheltered area at the back of my house. These include Tetrapanax ‘Rex’, tree ferns (Dicksonia) and ginger lilies (Hedychiums), which I give some protection to in the form of fleece wraps and straw packing in the worst winters.

But probably in common with others who adopt this style of planting, I had been lulled into a false sense of security after the very mild winter of 2019-20. This meant that I’d left some things to fend for themselves and although they all seemed to survive, the tricky combo of warm days and cold nights has take its toll – particularly on my Tetrapanax. Its valiant new leaves have been shrivelled and looking at them now, I realise that perhaps I shouldn’t have chanced it. Anyhow, it’s happened so I have to hope they come back.

Is it safe to put bedding plants out

It is the more tender plants that need careful consideration. Certainly summer bedding plants are far too vulnerable to be outside during such risky weather. They all need cosseting indoors, in a well-lit place to grow on at least until mid-May to be on the safe side – particularly it seems, this spring!

All those baby plug plants are not only vulnerable in your garden, but at garden centres and DIY stores too. They should certainly have been protected overnight, but even during the daytime, temperatures in single figures are likely to give them a cold shock. This can stunt their growth and set them back by weeks – if indeed they go on to survive at all.

Far better to put off buying summer bedding plants until the beginning of May, when the fresher stock is likely to be happier and will grow away strongly. But even early May, in colder parts of the country, is too early for these tender plants to go out. But don’t despair – once it does warm up, these plants will make up for lost time, going on to grow quickly and flower in the long summer days.

Will there be fewer plant pests after the cold winter

One of the biggest benefits, however, from all that cold weather is likely to be a much reduced level of pests and diseases – certainly to start the summer. The frost will have killed off the overwintering eggs, larvae and adult of many pests, as well as the spores of some fungi. And garden birds, frogs and other wildlife have been on the hunt for food during the cold conditions, so should have hoovered up lots of the eggs and larvae too.

This means that pests and diseases will start from a lower baseline and generally are unlikely to reach their peak until midsummer, when much of the soft spring growth has toughened up. A bit of a silver lining for gardeners!

Ways to help plants after cold weather

So what should you do if your plants have had a side swipe from the frost? Here are my 5 top tips to help give your plants the best chance of recovery.

1. If the flowers of magnolias and camellias have been blackened by frost, it’s a good idea to pick off as many of them as you can reach. This will not only make them look better, but it will remove dead tissues that could be a source of fungal infection in the coming months.
2. Where the soil is very dry and you haven’t had much in the way of rainfall over the last month or so, it would benefit border plants and young shrubs to give them a thorough soak at their roots to prevent them drying out and to fuel growth when it does start.
3. While the temptation might be to feed plants to try to help them recover it should be avoided until the warm weather returns and growth get under way. The nitrogen in many fertilisers can promote soft growth which is even more vulnerable to frost and drying out. In addition, adding fertilisers to dry soil can cause any available moisture to be sucked away from where plant roots can use it.
4. Have some horticultural fleece or old net curtains to throw over vulnerable plants to prevent further damage on frosty nights. You could also use recycled removals blankets (if you have them) or other improvised overnight coverings. This will direct the cold descending air away from the foliage and delicate buds.
5. Once healthy growth does get started again, by late April or early May, then use a sharp pair of secateurs to prune out any dead growth, cutting back to healthy buds. Having been held back by the cold, you’ll be amazed at just how strongly many plants in your garden will grow when the warmth does arrive.