August can be a very warm month, and increasingly we are seeing periods of extreme heat across northern Europe. In southern Europe, temperatures of 30–40°C can place severe stress on many temperate-climate plants, whether large or small.
Ideally, periods of high heat would be balanced by rainfall and cooler nights. In reality, this often does not happen until much later in autumn. By then, invisible damage may already have been done if plants have not received enough water.
I try to do as much watering as possible from water butts and always water either early in the morning or in the early evening, especially after a prolonged dry spell.
During a tour of Australia and New Zealand, I spoke to gardeners and head gardeners about the plants they grow. Many of the species used there are adapted to storing water or surviving with much less rainfall than plants typically grown in the UK. It was a valuable reminder of how strongly climate affects what can and cannot thrive in a garden.
U.N. Climate Action
Hotter countries have trees, plants and edible crops that have adapted to warmer or colder weather patterns, but even these can struggle when climatic conditions continue to change.
Average global temperatures have risen more rapidly since the period of increased industrialisation following the Second World War, alongside rising carbon emissions.
This is why climate change conferences led by the United Nations are encouraging countries, rich and poor, to take future carbon emissions seriously. These emissions come from fossil fuels, agriculture, food production and livestock, among other sources. Poorer countries naturally have less flexibility and fewer resources with which to respond.
There are also concerns around hydrocarbons stored underground over millions of years being released as permafrost begins to thaw in very cold regions such as northern Russia and Greenland. Innovation may offer opportunities to capture some of these emissions at source.
There is, however, also reason for optimism. Increasing investment is being directed towards tackling this enormous problem. Private and public organisations have a strong incentive to develop solutions, including carbon capture, reduced dependence on coal and oil, and greater use of renewable energy.
Renewable energy is increasing significantly and this is an important part of the solution.
Nuclear power remains a fallback source of energy internationally, but it is extremely expensive and very slow to construct. We are particularly aware of this here in the North Somerset area. Waste disposal also remains a concern, although improvements in reprocessing may provide better long-term options.
Science will, I believe, continue to find solutions. The important question is how quickly those solutions can be developed and adopted.
Plants for Hotter, Drier Summers
Where space allows, I recommend adding ground-cover plants. These can help hold moisture in the soil and protect it from strong summer sun.
Useful choices include:
- Hardy geraniums
- Alchemilla mollis, or lady’s mantle
- Astrantia
- Erigeron
Members of the daisy family are also extremely popular at this time of year. Rudbeckia and Chrysanthemum can provide excellent late-summer colour, while annual Calendula works particularly well in a well-watered pot.
What to Look For in Your Garden
Take time to observe how your garden has responded to this summer.
Have any plants suddenly disappeared or died since last year?
Are some plants looking happier and thriving?
Are others struggling unusually?
Think about the possible reasons. Position can be vital: is the plant receiving too much sun, too much shade, or simply not enough moisture?
Pruning after flowering can also encourage strong new growth.
Replacing Nutrients in the Soil
My own soil often needs nutrients replacing after winter, particularly following periods of heavy rain that can wash nutrients away.
Liquid NPK feeds can be extremely useful as plants approach flowering.
Nitrogen supports green leaf growth and photosynthesis.
Phosphorus supports roots and stems and helps build strength.
Potassium supports flowering and fruiting.
Some feeds also include magnesium as a useful micronutrient.
Tomato feeds are generally high in potassium and can be very useful for encouraging flowering and fruiting plants.
Feeding Rhododendrons and Ericaceous Plants
If you grow rhododendrons or other ericaceous plants, only use feeds specifically designed for acid-loving plants.
Liquid ericaceous feeds are useful during flowering, while solid versions can help improve the soil over a longer period.
Horticultural sulphur powder can also be used where faster acidification is required.
Ask Tony
If you have a science-based gardening question, Tony is happy to help.
Email: tony@scienceforthegardener.com
Tony Arnold MCI Hort
Secondary Science Resource
RHS Schools Gardening
Tony is also the author of Science for the Gardener, available as a signed copy here:
Science for the Gardener — Signed Copy
This article was originally written by Tony Arnold for his local community magazine the Drift and has been adapted for the Science for the Gardener website.