HEADING into the second half of July, our attention turns to plants that provide late summer and autumn colour. But, this year, we also need to think about drought. Summers aren’t always this hot in this part of the world, but with climate change, we can expect more extremes, in terms of storms in the winter and droughts in the summer. Clever gardeners will have to be prepared.
My first RHS Chelsea Flower Show was when I was a horticultural student in the UK and our college was building a show garden there. It was a drought-resistant garden, in 1991, which illustrates that hot, dry summers are not new in this part of the world, particularly not in the south of England.
Whether or not extremes like this year become the norm or are remembered as freaks, it still makes sense to use plants that will survive hot and dry periods.
I am always stressing to new gardeners the importance of helping plants to establish in their first year in a new garden. What this means is that they get enough water. That may be rainwater or from the hosepipe, but they will need to be watered, as their roots aren’t established enough to source their own.
There are further ways to help and, in particular, mulching, applying a layer of bark chippings, or any other organic material around the root zone of the plant, to a depth of three to 7-10 cm, will substantially reduce water lost through evaporation. Once established, many plants will then survive periods of drought and high temperatures.
While I don’t remember all the plants that we used in the show garden at Chelsea 27 years ago, I do remember some. There was a particularly interesting small shrub, X Halmiocistus ‘Merrist Wood Cream’.
Interesting botanically, because it is an intergeneric hybrid, a cross between plants of two separate genus, namely Halmium and Cistus and also of interest because it was bred in, and named after, the college I attended, Merrist Wood, in Guildford.
It’s a very attractive, low-growing, evergreen shrub, with grey/green foliage and masses of very pretty, cream-coloured rock-rose-type flowers with a very dark centre.
Plants that you should choose for drought resistance include those with silver or grey foliage and also those with waxy leaves, as they will lose less moisture through transpiration than those with flat, soft leaves. Plants transpire through the leaf surface, so choosing ones that produce foliage with a smaller surface area will also make sense, such as those that produce needles and spines rather than leaves. Many grasses, too, will work well for the same reason.
A good grass to use is Festuca and particularly the variety ‘Intense Blue’. This is a low-growing, clump-forming, ornamental grass, which creates a bright blue, pincushion effect in the garden. Heliotrochon sempervirens will give a similar blue colour, but will grow to a much larger, 80cm or more
Many alpine plants will tolerate very dry conditions. Examples are Armeria maritima, the Sea Thrift, which can be seen clinging to outcrops of rock and sand dunes all along our Atlantic Coast. It gives a wonderful display of pink flowers earlier in the year.
Cerastium tomentosum, known as ‘Snow in summer’, is a silver-leaved Alpine plant that will cover a good-sized area like a carpet, producing masses of white flowers during early summer, hence the common name.
Lavenders, in all its shapes and sizes,is another good choice and, with regular trimming, will certainly continue flowering right up to early winter.
A plant that complements Lavender beautifully is Perovskia ‘Blue Spire’ or the slightly lower-growing form, ‘Little Spire’.
This Russian sage needs nothing like the maintenance of Lavender, no regular trimming.
One good haircut in early spring will pay dividends from now on, as blue flowers are produced on silver grey stems to create an effect of a blue haze, perfect on these long, hot, summer days.
Fleshy-leaved plants, such as Sempervivum, (Houseleeks), and Sedums will store water in their fleshly foliage, a bit like horticultural camels, and will thus survive long periods without water.
Do look out for the Sedum ‘Jose Aubergine’, which I have in my garden, just about to burst into flower beneath a pure white Leucanthemum, ‘Wirral Supreme’.
The deep-purple leaves and paler-coloured flowers are brought to life by the bright Leucanthemum.