Drought Tolerant Planting Design for a Changing Climate
Gardens are having to cope with increasingly challenging growing conditions. Hotter summers, prolonged periods without rain and water restrictions are becoming more familiar to gardeners across the UK.
This makes drought tolerant planting design increasingly important when designing a garden. Choosing plants that can cope with dry conditions can reduce the amount of supplementary watering required and create a garden that is more resilient during periods of drought.
But drought tolerance isn't simply about filling a garden with Mediterranean plants. Some of the plants that have performed particularly well in my own Hertfordshire garden this year are ones I wouldn't necessarily have expected to thrive during a long, hot and dry summer.
That has made this year's conditions an interesting opportunity to see which plants can genuinely cope.
Why drought tolerant planting matters
When choosing plants, it's easy to concentrate on how they will look when first planted. But a successful planting scheme needs to consider how those plants will perform over many years and under increasingly variable weather conditions.
Plants that need consistently moist conditions should ideally be planted where there is naturally available ground water, or where irrigation can reliably provide it. Otherwise, keeping them alive — let alone looking healthy and attractive — can become a constant battle.
This is particularly important when designing a garden for the long term. It is possible to keep the wrong plant alive with enough watering and attention, but that doesn't necessarily make it the right plant for the site.
Drought tolerant planting is about selecting plants that can cope with periods of limited water once they are established. This doesn't mean they never need watering. Newly planted plants still require regular irrigation while their root systems become established.
The aim is to create planting that becomes increasingly self-sufficient as it matures, rather than a garden that relies on constant intervention to keep unsuitable plants alive.
How do plants survive drought?
Plants have evolved a remarkable range of adaptations to survive in hot and dry environments. Their leaves, stems and roots can give us clues about how they have adapted to cope with limited water.
Small leaves
Small leaves reduce the surface area from which water can be lost through transpiration.
Many plants from dry environments have relatively small or narrow leaves for this reason. Less leaf surface can mean less water loss during periods of heat and drought.
Silver and grey foliage
Silver or grey leaves are another common adaptation.
The pale colour helps reflect intense sunlight, reducing the amount of heat absorbed by the leaf and therefore helping to limit water loss.
This is one reason plants such as Lavandula, Stachys and Euphorbia can be so effective in sunny, dry planting schemes.
Fine hairs
Some plants have leaves covered in fine hairs. These can help reflect sunlight and create a layer of still air around the leaf, reducing water loss.
The hairs can also help trap moisture from the atmosphere, including early morning dew.
Waxy and glaucous leaves
A glaucous leaf has a characteristic blue-grey or silvery appearance, often caused by a waxy coating on the surface.
This coating can help reduce water loss and protect the leaf from intense sunlight.
It is particularly noticeable on many drought-adapted plants and is one of the visual clues we can look for when selecting plants for dry conditions.
Deep roots
Some plants cope with drought by developing extensive or deep root systems.
Rather than relying on moisture close to the surface, these plants can access water further down in the soil.
This is one reason why the conditions beneath the surface are just as important as what we see above ground when designing drought tolerant planting.
Succulent foliage
Succulent plants have evolved to store water within their fleshy leaves or stems.
Their ability to hold reserves of water allows them to survive extended periods of dryness.
Sedums and other members of the Crassulaceae family are familiar examples and can be particularly useful in sunny, well-drained situations.
Drought tolerant plants that have performed well in my Hertfordshire garden
This summer I have been paying particular attention to how the plants in my own garden have responded to the prolonged dry conditions.
My garden is in Hertfordshire and has improved clay-loam soil. I haven't watered the established planting, other than newly planted plants. The results have been interesting because some of the plants I expected to struggle have performed surprisingly well.
Full sun
These are the plants that have performed particularly well in sunny positions:
Agapanthus africanus
Alchemilla mollis
Calamagrostis × acutiflora 'Karl Foerster'
Echinops ritro - newly planted and watered only around twice a month
Foeniculum vulgare
Gaura lindheimeri
Euphorbia seguieriana subsp. niciciana
Euphorbia myrsinites
Geranium 'Rozanne'
Hylotelephium
Iris germanica
Lavandula angustifolia
Miscanthus sinensis
Molinia caerulea 'Transparent'
Origanum laevigatum
Papaver somniferum
Pittosporum tobira 'Nanum'
Rosa - various cultivars
Stachys officinalis 'Hummelo' - newly planted and watered only minimally
Verbena bonariensis
Centranthus ruber
There are some obvious drought-tolerant choices here, such as Lavandula, Euphorbia, Agapanthus and Hylotelephium.
But there are also plants that might not immediately spring to mind when thinking about drought tolerant planting.
Alchemilla mollis, for example, is usually associated with relatively moist garden conditions, yet it has coped remarkably well in my garden.
The ornamental grasses have also performed strongly. Calamagrostis 'Karl Foerster', Miscanthus sinensis and Molinia caerulea 'Transparent' have all continued to provide structure and movement despite the dry conditions.
Geranium 'Rozanne' has also performed particularly well, continuing to flower despite the lack of supplementary watering. Centranthus ruber has similarly coped well with the dry conditions.
Roses have also surprised me. Established plants have continued to flower and grow without supplementary watering, demonstrating that drought tolerance isn't necessarily restricted to plants traditionally associated with hot, dry climates.
Part shade
The selection becomes more interesting when moving away from full sun.
These plants have performed well in part-shade conditions:
Astrantia major 'Roma'
Hakonechloa macra
Herniaria glabra
Luzula sylvatica
Polypodium vulgare
Again, several of these wouldn't necessarily be the first plants I'd associate with drought tolerance.
Hakonechloa macra, for example, is generally regarded as a plant that appreciates moisture, yet established plants in my garden have coped well with this year's dry conditions.
This highlights an important point: plant performance is highly dependent on context.
Soil, aspect, root competition, establishment, shade and the wider microclimate can all have a significant influence on how a plant responds to drought.
Some of the results were surprising
One of the most useful things about experiencing an unusually dry summer is that it challenges our assumptions.
Not everything that is described as drought tolerant has necessarily thrived in my garden this year. Lychnis coronaria and Phlomis russeliana, for example, are plants that I would expect to cope well with dry conditions, yet both have suffered during the prolonged drought.
I've also had several plants that I knew were not particularly well suited to extreme dry conditions, including Hydrangea paniculata, Veronica longifolia, Persicaria amplexicaulis and Persicaria affinis, amongst others.
Initially, I tried to keep these plants going with additional watering, but it became clear that they simply weren't going to be suitable in the long term. Some of them have survived previous summers with relatively little attention, but this year's conditions have highlighted the difference between a plant that can tolerate an occasional dry period and one that can genuinely cope with prolonged drought.
I could continue watering them to keep them alive, but I don't think that is a sensible long-term approach. If a plant requires regular intervention simply to survive, it is probably the wrong plant for that particular situation.
I'll therefore be looking at replacing some of these plants in the autumn with species better suited to the conditions.
This is one of the most valuable lessons from this year's drought: good planting design isn't just about choosing plants that can survive. It's about choosing plants that can thrive in the conditions you can realistically provide.
A plant that thrives in a hot, free-draining gravel soil may respond very differently when planted into improved clay soil in Hertfordshire. Equally, plants that we don't traditionally associate with drought tolerance can sometimes perform remarkably well when established in the right conditions.
The experience has reinforced for me that there is no definitive list of "drought tolerant plants". Plant performance depends on the combination of plant, soil, aspect, drainage, root competition, establishment and microclimate.
The best planting design works with those conditions rather than constantly fighting against them.
Drought tolerant doesn't mean Mediterranean
When people think about drought resistant planting, they often picture Mediterranean gardens filled with lavender, rosemary, thyme and ornamental grasses.
These plants certainly have an important role to play, particularly in sunny, well-drained situations.
But a climate-resilient planting scheme doesn't need to look like a Mediterranean garden.
My own planting demonstrates that there is a much wider palette available. Ornamental grasses, roses, perennials and plants traditionally associated with woodland or cottage-garden planting can all have a role, depending on the conditions.
This is particularly useful when designing gardens in the UK, where we still need plants that can cope with cold winters, wet periods and sometimes heavy soils as well as summer drought.
The objective isn't to recreate another climate. It is to select plants that can cope with the conditions we are increasingly likely to experience here.
How to establish drought tolerant planting
Even the most drought tolerant plant needs water when it is first planted.
A common mistake is to assume that planting drought tolerant species means irrigation can be avoided altogether.
New plants have small root systems and need sufficient moisture to establish. Regular, deep watering during the establishment period encourages roots to explore the surrounding soil.
Once plants are established, watering can gradually be reduced depending on the species, soil and weather conditions.
Other factors can also help:
Improve soil structure where necessary.
Apply a suitable organic mulch to help reduce evaporation.
Avoid unnecessary disturbance of established soil.
Choose plants suited to the actual conditions of the site.
Group plants with similar water requirements together.
Mulch new planting to help retain soil moisture.
Consider irrigation during the establishment period rather than relying on permanent high levels of watering.
Good planting design is ultimately about putting the right plant in the right place.
Designing gardens for a changing climate
The weather we experienced this summer is a useful reminder that planting design needs to look beyond the first year after installation.
A garden should be designed to be beautiful, but it also needs to be resilient.
That means thinking carefully about soil, aspect, drainage, exposure, plant selection and how much water a garden is realistically going to receive.
Drought tolerant planting design is not about creating a garden where nothing needs water. It is about creating a planting scheme where plants are selected and positioned so that, once established, they can cope with periods of drought with much less intervention.
The result can be a garden that is more sustainable, lower maintenance and better adapted to the conditions we are likely to experience in the future.
And, as I've found in my own Hertfordshire garden this year, sometimes the most useful lessons come from the plants you least expect to succeed - and those you expect to succeed but don't.
If you are considering a redesign of your garden, we'd be delighted to hear from you:
Contact us at dan@danhartleygardens.co.uk to discuss your project!
Comments