All living things need water to survive and plants are no exception. Plants can adapt to their growing conditions, but many of the plants that we grow in our gardens are not native to Britain and can actually originate from all over the world. By choosing plants that tolerate the conditions from a hotter climate, they stand a better chance of survival when we have a hot summer.
Drought tolerant indicators
Plants are quite amazing in that they actually give us clues to indicate whether they are well suited to hot conditions. If you can learn to recognise some of these, then you are on the right tracks to choosing suitable plants to grow in hotter conditions.
Think about the plants that grow in hot Mediterranean countries. Many have silvery foliage and if you look closely you will often see that the leaves have tiny hairs on them: lavender is a good example. The tiny leaf hairs protect the surface of the leaves and reduce evaporation. Hairy leaves actually shade themselves with their own hairs forming a protective layer over the more delicate tissues – Verbascum bombyciferum and Stachys byzantina (lambs’ ears) are just two easy-to-grow examples.
The shapes of leaves can give us many clues, for example, plants with long thin leaves such as grasses or rosemary have fewer stomata (leaf pores) and so evaporation from the leaf surface is much reduced. Plants with small leaves, such as thyme, or leathery leaves, such as sage or cistus, are also slower to give up precious water.
Spines can act as cooling fins on a plant, so these are often seen on more drought tolerant plants such as cacti and succulents but also ensuring plants like Acanthus spinosus (bear’s breeches) and Eryngium oliverianum (sea holly) lose heat but not too much water.
Aromatic foliage is another indicator, the volatile oils evaporate at the leaf surface it actually cools the leaf. Good examples are rosemary, lavender and thyme
Fleshy, succulent leaves store moisture for dry spells. The on-trend sempervivums are a great example, as are sedums such as Sedum spectabile (the ice plant).
And of course some plants use several of these mechanisms at the same time, giving them more defences against the scorching heat of the sun.
Other good, more drought tolerant plants include pelargoniums, gazanias, osteospermum, Plectranthus, mesembranthemum and helichrysum.
But, just because a plant is more tolerant to drought does not mean you can neglect it. Plants in containers can dry out very quickly and any plants in small pots, or that have been recently planted will need access to water to become established. An established plant is one that has put its roots into the soil to access the moister soil conditions deeper down. Once it has done this it will be much more tolerant to dry spells.
For more advice on dealing with drought in your garden click here.