The summer of 2022 has certainly been a challenging one, and at the time of writing it’s still not over.
A little background: I live on Dartmoor in Devon, which, for anyone not familiar with the geography of the UK, is on the bottom left hand corner of England. To the west is Cornwall, and beyond Cornwall is the Atlantic Ocean. The prevailing wind here comes from the south west, bringing lots of moist air from the sea onto the land. The central ‘spine’ of Cornwall gets a lot of mist and rain, but usually there is still plenty to share with western parts of Devon, especially Dartmoor. High up on the moors the landscape can be very bleak and desolate, with seemingly never ending rain keeping the sweeping contours of the hills a delightful shade of green. Unless it’s misty, in which case you can’t see anything!
The profusion of water in my area (Devon and Cornwall) gives us a startling verdancy. This is a bountiful place, with Rhododendrons, Camellias and Magnolias in particular happy to take full advantage of the mild winters and abundance of rainfall. The joke in these parts is that a drought is any two consecutive days without rain.
This has made the sudden heat and long drought of this summer particularly challenging. While other parts of the UK, namely the south eastern region, are more used to long periods of heat and drought it’s not something we really get in this area. Consequently our gardens aren’t prepared for it when it comes.
This has certainly been an interesting year to make observations, and I’d like to share some of those observations here. To people living in normally hot and dry regions these observations will have little relevance.
I’ve been mulling over an idea that I’ve referred to as ‘buddy planting’ for some time. The idea is that plants are given a ‘buddy’, another plant of similar growth habits and a complementary look, to help them through wet winters. The idea, at least in my mind, is that planting Salvia yangii ‘Blue Spire’ with one of the smaller evergreen grasses would not only look good but the grass would buffer the Salvia from the effects of winter rain. I’ve not really been able to try it out in any meaningful way yet; I was going to try the experiments in my own garden but opted to fill my garden with other plants instead! I think I also had this vague idea that plants would benefit from this sort of thing in summer too, but I’d not really put much thought into it.
It’s become blatantly obvious this summer, however, how beneficial plant ‘communities’ are. The only things I’ve watered in my garden (excluding pots) are newly planted plants. The rest of the planting has been perfectly happy without intervention for weeks, or at least the more established planting has been. I’d theorised that transpiration from plants growing together kept the atmosphere between them humid and that humidity reduced collective transpiration. I think there’s probably truth to this, but I’ve also made a far more startling observation of the importance of shade. We know that shade is important; when it’s hot and sunny we gravitate to the shade of a tree rather than roasting in the direct sunlight. That’s not exactly new information, but measuring surface temperatures has been far more enlightening.
On one particular day I decided to look at temperatures in my garden. The ambient temperature was 28ºC (82.4ºF) with a barely discernable breeze. The temperature of bare soil in my garden, soil directly open to full sun, was 46ºC (114.8ºF), and yet the bare soil in the shade of a small and recently planted Solidago was just 31ºC (87.8ºF)! I was astonished at such a major difference, having anticipated a difference of only a few degrees. This reinforced the impression I’d had at one of my gardens where a carpet of Silene dioica had all but hidden the young Rhododendrons that I’d planted back in spring. I’d expected to see lots of dead plants after the first heat wave, but when I looked closely the majority were fine. Logically you’d assume that a dense carpet of ‘weeds’ would steal moisture and be detrimental to the young plants. I don’t think that’s an illogical idea really… yet I’ve come to the conclusion that any moisture ‘stolen’ by incidental flora in a garden is offset by the benefits of having the ground shaded from the effects of direct sunshine.
New plantings have been a little harder to deal with as invariably plants aren’t as well rooted and even closely planted they will have space between to allow for growth. Here I think is where mulching will be most beneficial, not just to ‘keep moisture in’ (which is one of those things that might in fact only be partially true) but to distance the heat of the sun from the soil. Essentially I’m thinking that the benefits of a mulch are insulation, not as a barrier to try and keep moisture in. Hot dry soils will lose moisture of course, but the mulch keeps soil temperature down and therefore reduces heat loss.
I tried this theory out in a garden where we use cut bracken and ferns as a mulch (see picture above). Freshly laid bracken had a surface temperature of 56ºC (132.8ºF) in full sun while underneath it was just 26ºC (78.8ºF). Had the bracken been laid onto a cooler soil surface to start I’m confident that the soil surface temperature would have been lower; these figures are quite impressive given that the 30cm (12”) layer of bracken had been laid just two hours before the temperature was measured.
So yes, I think the benefits of shading the soil have become abundantly obvious to me this year, and this is certainly going to be one of the observations I’ll take forward to try and improve my work. While I’ve been reading on social media about people and gardens cutting their meadows because you always cut your meadows in August… I’m leaving mine until the weather cools. On a human level cutting grass manually (ie not with a tractor) in extreme heat is inhumane and places that have told their staff to ‘man up’ and do the job now because this is when it needs doing should take a long hard look at how they treat their staff. On a more environmental level, a cursory glance at long grass shows that the base of the grasses, and often the wildflowers too, are still green. Cutting now, in a drought, will expose the plants in the meadow to enormous heat, drying the ground and making it hard for any but the most resilient plants to recover. And what of the seeds? Those important seeds that get knocked down to the soil surface will be exposed to the dry, desiccating winds and the baking heat of the sun…
One thing I would like to touch on before I move on from discussing shading the soil, and still with the ‘buddy plant’ idea, is to mention another observation: even among the more established plants, including large trees, the greatest stress is being shown by plants growing in isolation. It’s not just herbaceous plants that are benefiting from being part of a plant ‘community’, it’s woody plants too. Looking out of my window I can see a woodland; it looks from here as though there is a little yellowing of the Nothofagus plantation but otherwise the woodland appears nice and green. The woodland is a community of trees. Similarly in the garden I was in just a couple of days ago the happiest plants were those growing together, for example nice big plantings of Camellias were green and healthy looking in full sun while isolated Camellias in a little shade were looking stressed. Gardeners tend to have something of the ‘stamp collector mentality’; we tend to treat plants as ‘specimens’ to be looked at individually rather than taking inspiration from natural habitats. I’m as guilty of this as anyone, but I do wonder if we shouldn’t try to shake this idea from our conscience and look at creating ‘plant communities’ with woody plants as well as herbaceous plants?
One of the gardens in my care is predominantly a woodland garden. Rhododendrons, Camellias, Magnolias and a wealth of other beautiful plants are grown under a canopy of Liriodendron, Cercidiphyllum, larger Magnolias, Eucalyptus, interspersed with native Quercus, Tilia etc. In one particular area there is what could only be described as a ‘matrix’ planting of trees, or as I think most gardeners would say “the trees were planted too close together”. Here Acer cappadocicum, Halesia, Aesculus hippocastanum, Acer platanoides and Acer davidii grow perfectly happily together. If we sped up time we would probably see them all jostling for position, trying to take the best of the sunlight before their neighbours get to it. Individually none of these trees would win a prize in a beauty contest for trees, but collectively they make an attractive grouping. When you look at the world more widely you see that this ‘tree community’ thing is common; I can see trees doing exactly the same thing in the woodland outside my window.
Getting away from this ingrained ‘specimen’ mentality will be difficult for us all. When you plant a tree you instinctively want it to be the greatest example of that tree that has ever lived, and the idea of sacrificing that noble goal is abhorrent to us. But maybe as our world changes and our understanding develops this idea won’t seem quite so bad? The Halesia in the planting discussed above flowers well every year, but the only way to experience the hanging white flowers is to glimpse them through the canopy, to snatch a view of them against a bright blue sky. Far from being frustrating it’s actually really exciting; you must look, and this active experiencing of the tree in flower makes the experience more precious than the passive glance from a distance. Of course there will be very special trees that we want to highlight; maybe we design a space for them in our community planting? Maybe rather than having one example of a special tree we plant several, making a specific planting to highlight the importance of the species or cultivar? After all, if any tree is special enough to have one then it is also special enough to have several.
The hot and dry weather has also really brought home to me the importance of heat on lawns and hard surfaces. It’s quite astonishing how hot paving slabs and gravel can get in direct sun. We know that walking across these surfaces with bare feet or thin-soled shoes can get quite uncomfortable, but it’s only when you start measuring temperatures of up to 60ºC (140ºF) that you realise that it’s not just an impression of heat, it’s actually very hot! Artificial turf warms up incredibly quickly and can reach similarly dangerous temperatures (particularly if you inadvertently decide to walk on them with bare feet!). In the UK home insurance companies are starting to take the risks of injury from artificial turf very seriously, both in terms of possible personal injury and more general problems with water management from large areas of hard surfaces. It’s likely that many people who have artificial lawns will find themselves needing additional insurance cover in the future.
The differences between temperatures in grass of different lengths was quite a surprising discovery. At a garden with a sports area the grass was mown on a day with an ambient temperature of 28ºC (82.4ºF). Where the grass was cut to around 1cm the temperature was measured at 38.7ºC (101.7ºF), but a nearby area with grass 2.5cm long was just 21.5ºC (70.7ºF). I know which I’d rather be walking on! (Incidentally one of my gardens has a very short lawn which is now ‘dead’ in a bit of a heat trap, and the brown grass was 60.4ºC (140.7ºF)!) Leaving the lawn a little longer in hot weather really does make a big difference, yet our local authorities are still mowing grass down (due to contractual obligations) and domestic gardeners are still insistent on mowing their lawns as short as possible even during extreme weather; the desire for ‘tidiness’ is so strong in some people, yet during hot and dry spells you must decide if you want your grass short or green.
It’s amazing how quickly things are forgotten. This is, I guess, my reason for writing this piece. The rain returned to this region in September and was much appreciated. I had feared that the rain would arrive as a relentless deluge and cause extensive flooding, but I’m relieved to say that the rain arrived in short periods, slowly replenishing the moisture missing from the ground.
I’m still, a few months later, finding soil that is dry beneath the surface; I suspect that we will need a great deal more rain over winter if we’re not to face difficulties again next summer.
Most of the plants that have struggled this year are making a reappearence; Hydrangea serrata cultivars completely wiped out by the heat and drought are making significant growth from the base, while a fine clump of H. aspera from Taiwan growing in a difficult spot are sprouting up the stems. Gardeners will need to prune a lot of dead wood out of trees and shrubs over the next year or so, but for now I’m inclined to leave trees and shrubs as they are for the moment, partly to see how they recover and partly so that dead material can protect tender new shoots from weather and deer.
At this point my particular fears are for Magnolias and Betula in one particular garden. The Magnolias are showing little enthusiam for rebirth, and the fate of Betulas on thin soils are far from certain. Patience is a virtue and it’s not sensible to try and rush the delicate process of recovery.
My lessons for the year are as follows:
1. While mulches are of absolutely no use if there is no rain at all over a long period they do provide much needed shade for soil, and thus also roots, exposed to direct sunshine. This poses a little difficulty with groundcover herbaceous plants like Geraniums that prevent the application of deep mulches.
2. Plants should be grown more closely together if possible, embracing the idea of creating a matrix of plants in woody plantings as well as herbaceous plantings. This will create more resilient communities of plants.
3. It would be wise to return to late summer and autumn planting to reduce need for heavy watering.
4. Pots are a liability in hot and dry weather, and numbers should be reduced. Where pots are used plans should be made to shield them from excess heat; this could be as simple as moving pots to the shade of a tree or covering them with a sheet of frost fleece.
5. Greater care should be taken to encourage plants to become more self-sufficient. Adopting better watering practices, plus the use of mycorrhizal fungi and anionic surfactants, and increased use of mulches when plants are young would be a good start, but gardeners should remain open to new techniques and ideas.
6. Better understanding of, and flexibility towards, lawns and other grassed areas would be profoundly beneficial.
It would be unwise to focus efforts on drought resistant planting in areas still normally experiencing wet conditions. In the UK it’s believed that the climate of western parts will develop towards more powerful winds/storms and more extreme rainfall, and if this does indeed prove to be the case then gardens planted here for drier conditions will struggle. We must, however, accept that periodically we will experience unusual extremes. My feeling is that focussing our efforts purely on what we grow would be foolish, and we must also focus on how we grow plants too.
Building resilience into our gardens will primarily need a change in how we think about gardens. Yes we may indeed need to change the structure and the nature of our gardens in some ways, but instead of looking for simple ‘quick fixes’ we should adopt a more philosophical approach. Bioswales and rain gardens should be considered when designing or redesigning areas, drains should be built with additional capacity when already being installed or upgraded, and greater thought given to creating resilient planting for whatever the future brings.