How to revive your garden plants after extreme weather
An up-and-down spring – with frosts followed closely by heatwaves, all the while with very little rain in many regions – has left plants distressed as summer sets in.
Many dahlias and potatoes were frosted and are slowly recovering. Some potatoes have been so weakened that they might never regain even a part of their potential. They might as well be replaced with something else if recovery is weak – although if you have any seed tubers left, replanting is an option. Dahlias seem made of sterner stuff, regrowing strongly and relishing the recent heat.
Incautious early planting of courgettes and cucumbers has often resulted in fatalities. There is still time to resow these. They will grow swiftly in the warm soils and sunny June days.
Weeds have been held back by the dry weather, but those that have grown enough to reach the soil moisture made quite a surge in growth during the heat. Where the weather is dry they will perish easily after hoeing, but in rainy conditions a gloved hand to remove them before they can set seeds is unavoidable.
On plants such as lilies and onions, flecked leaves but unaffected more recent growth suggests hail damage. The marks are mostly cosmetic. The damage has not allowed diseases to enter the plant, but won’t disappear.
At least the soils remain moist at depth from the winter rains. Once new plants have established, they can access this water that may well sustain them until August, even if there is little summer rain.
Watering then should be just enough to wet the rootzone, keeping seedlings alive and growing until their roots reach the moister lower soil. There is no need to soak plots yet.
In fertile soils there should be enough plant nutrients to sustain growth. When they find the soil water, they will also find the soil nutrient reserves. If in doubt, consider watering with seaweed-based fertiliser.
Sowing annuals such as poppies is a quick, cheap way to replace plants lost in the heat.
The very hot days led to many plants – the cabbage family and potatoes, for example – stopping growing, and some may be stunted. They may even be showing wilting, scorched or browning leaves. With less intense heat, growth should resume and plants will grow out of their recent distress. Extra watering and feeding are unlikely to help.
Broad beans and peas, now in flower, will respond to watering by setting more pods. Peas hold up to heat better than beans. Watering before flowering leads to more leaves, but not more pods.
Broad beans may be carrying blackfly, but levels don’t yet need managing.
RHS entomologists don’t yet expect an insect surge as we had in last year’s drought. On the other hand, powdery mildew is appearing, notably on apples. Where apples are not carrying a heavy crop, which is common after the late spring frosts, the opportunity exists to prune out mildewed shoots. At the same time, overgrown or unwanted shoots can be removed without losing any crop.
Planning June sowings will avoid sowing in July, which is often second-best. Biennial flowers, for next year, are classic seeds to sow in June: Canterbury bells, foxgloves (inset far left), hollyhocks and sweet Williams, for example, before mid-June, and autumn vegetables and salads before the end of June – chicory, endive and Florence fennel are especially rewarding for autumn.
