How to save water with intelligent Xeric Gardening or Xeriscaping – even in cooler climates!
Water is an extremely precious resource and is coming under increasing pressure in many places around the world, and clean water is increasingly prioritized during periods of drought due to climate change or poor water infrastructure management.
For this reason it is simply unrealistic to plant up are large area of garden with ornamental plants that require constant watering – especially in areas of low rainfall or water use restrictions.
Even if your climate can support pretty thirsty plants, it is still an advantage to design a part of the garden which enjoys a drier aspect, and which can be used to harvest excess water runoff from the well-drained ‘Xeriscape’.
If you live in an area where the rainfall is naturally low and/or infrequent with an abundance of warm or hot weather, then it would be crazy to plant anything else.
A Xeriscape consists of the same basic elements as any garden – there is still soil, plants, climate and landscape, but there is a little more creativity involved as it often involves coaxing plants to be happy in a climate where they may not naturally thrive.
Xeriscapes can be incredibly stylish as they allow bold shapes and forms to be made by the landscape itself, using features such as large rocks, hills and hummocks, drainage channels, walls, dry ‘creek beds’. Equally striking shapes can be formed by the diverse plants themselves.
In many ways, Xeriscaping is often thought of as a special form of rock-gardening, but in reality many Xeriscapes are designed without a single rock being used, and may look very similar to a traditional shrubbery or flower bed – although this seems like a bit of a missed opportunity to create something truly special.
The soil should be a compromise between what your dry-loving plants need or enjoy, and what your natural climate provides. If you have infrequent rainfall you may want to add a water-holding capability to your garden, either by allowing the water to naturally pool in low-lying areas to provide long-term moisture (as it soaks back into the ground), or by having a more managed approach with water draining into a sump and reservoir, from where it may be pumped back into the garden as irrigation water when needed. The upper layer of the soil should be pretty free-draining for most parts of the garden, although a moisture-holding layer is often incorporated underneath.
The looser and drier soil on the surface acts like a mulch which prevents evaporation directly from the soil. Roots from the plants are able to seek out and draw up moisture from below. To start with, a freshly-planted Xeriscaped garden may require a little supplemental watering to ensure good root establishment, but the watering should be infrequent enough to encourage root exploration.
The most important rule is to try and match the plants with the soil that they need. There is an abundance of plants which enjoy really well-drained, poor soil, and these can grow side-by-side with plants that need moister and more fertile soil. However, the soil they are in needs to be different. A usual way of accommodating this is to use free-draining soil on higher areas of ground (such as a mound or raised bed) and to have richer moisture-holding soil in the lower-lying areas where the water will naturally drain into after a heavy rainfall. Moisture-holding layers can incorporate naturally water-holding clay soil, and water-proof membranes which allow small underground pools or reservoirs to collect in areas where more thirsty plants are situated. Humus-rich organic matter is not usually a good idea, although it has a high water-holding ability. Many dry-tolerating plants have poor immune systems and cannot grow in soils where high levels of fungi or bacteria are present, such as rich organic matter.
It is very important to use a mulch layer when trying to limit your water usage. Loose stone chippings and gravel are both very suitable for this purpose. These materials help to keep the soil cooler in summer, and warmer in winter, and will limit water loss through direct evaporation.
Drought-tolerant plants often struggle with excessive moisture.
Most plants in temperate zones experience a winter dormancy. This corresponds to dry weather in milder climates, and extreme cold in colder climates. In some parts of South Africa, the winter season is wet and temperate, while the summer is dry and intolerable.
The natural growing patterns and accompanying water requirements of the plants needs to be carefully considered in the garden design. While plants are dormant they do not like much moisture, because they cannot use it and then excessive moisture will accumulate.
For most ‘regular’ garden plants this poses little difficulty as they have adapted to this climate and have a high resistance to fungal or bacterial pathogens. For Xeric plants however, the excessive moisture can be fatal, so if you live in a wet-winter area the plants will need to be very carefully chosen, and some overhead protection may be needed for certain plants such as Cacti or Succulents.
It might be necessary to design a ‘controllable’ draining system that allows water to pool or accumulate in the Summer months (where is can be reabsorbed by the soil as needed), but which can drain freely in the winter. Alternatively, all the run-off can be collected in a storage tank and dispensed through an irrigation system as needed, and excess winter water can be drained directly elsewhere (or used in a grey-water system).
Your best choice is clearly going to be plants that don’t need much water – and there are plenty of these to choose from. Many of them will be familiar as sturdy rockery plants such as rosette-forming ‘Rockfoil’ Saxifrages, Houseleeks (Sempervivum species) and Stonecrop (Sedum), whereas others may be less familiar, and perhaps more exotic than you thought possible.
Many species of South African succulents from the Mesembryanthemum family are perfect ground cover, including the well-known Delosperma cooperi, as well as other Delosperma species, Drosanthemum, Nananthus, and Aloinopsis.
Drought tolerant plants fall broadly into either being succulent, or somehow just hard as nails.
Many species of Penstemon and Salvia thrive in the well-drained dry soil of a Xeric garden, whereas they would perish if planted in the SAME PLACE, but in a well-watered ‘fertile’ soil. There can be many reasons for this, depending on the specific plants and climates, but it can be related to the way the plants roots develop in the soil, and how the moisture levels in the soil create an unfavourable microclimate for dry-adapted plants.
As mentioned earlier, many desert-dwelling species have a naturally low resistance to fungal and bacterial pathogens and the over-wet compost of a ‘typical’ garden will quickly bring about an early demise of such species.
Several species of Palm trees are incredibly hardy, and they form deep roots which suck out moisture from deep in the ground while providing shade and cover during extreme weather. Various other shrubby species may also be very suitable, with Cytisus (Broom) and tree-lupin varieties being especially well-adapted to sandy soil as they come from coastal and dry habitats.
Some frost-hardy Agave and Yucca species can be very striking, as is the more unusual Hesperaloe parviflora or Nolina texana.
In addition, many species of Cacti including a wide variety of Opuntia (Prickly Pear) species can withstand hard frosts and snow in a well-drained Xeric garden.
Many gardeners will try to mimic the natural environment of xeric habitats and include a full range of plant types from shrubs and trees, subshrubs and taller perennials, small low-growing perennials and succulents, and quick-flowering annuals such as Linum grandiflorum, Lupinus nanus and Escholtzia (Californian Poppy).
Climate and Water
One of the primary considerations with your Xeric garden design should be the role of your local climate and water situation. The whole point of a water-wise planting is that it should eliminate the requirement for supplemental watering, and may even contribute additional water to other, thirstier, parts of the garden (such as a Vegetable patch, or greenhouse) through the management of controlled runoff from the free-draining Xeric parts.
Are you trying to deal with excessive rainfall during the colder months, or are you desperate for every drop that falls?
These considerations will shape the way you design and construct your Xeric scheme as water may need time to pool (and soak in) in areas of ground, or may need to drain as swiftly as possible into a water-reclamation system. As with any garden, the ‘aspect’ is very important, as most Xeric plants will dislike too much winter wet.
The xeric garden is a landscape in miniature, both in terms of aesthetic and functional design. Aesthetic, because it should be beautiful and emulate or evoke the natural environment it seeks to mimic. Functional, because the design should contribute to the overall suitability of the growing environment for these environment-specifically-adapted plants.
A range of shelters and exposures should be provided and maximized, with south-facing (in the northern hemisphere) sun-traps that collect solar heat for ‘more tender’ plants, and surfaces that collect and channel runoff towards those plants that need more moisture.
Taller overhanging plants or architectural features can provide necessary shade and cool spots for plants that need these conditions.
It should be noted that most plants benefit from a part of the day where they are shaded in part, even those that can tolerate full sun.
The positioning of taller subjects should also be considered in relation to how the garden will be viewed, and how to avoid excessively shading-out plants that would otherwise require brighter growing conditions.
Construction of a full-sized Xeric garden may be quite a substantial undertaking if the entire environment needs to be created from scratch.
If, on the other hand, you are simply working with your ‘natually xeric’ prevailing environment then it is simply a matter of choosing the right plants for the right places, taking note of requirements for shade or full sunlight, and soil type (making amendments where needed).
It may be possible to incorporate the principles of water-wise Xeric gardening on a small scale as well, by using containers that have been planted with tough drought-tolerant plants, and this can be an excellent way to reduce water usage on a patio, balcony, or terrace garden.
Choosing Plants for Xeric Gardening
There are a great many plants to choose from, all of which have their own particular wants and needs, being more or less tolerant of winter wet and cold or summer drought.
This short list should be a good springboard to get started, with a range of plant types to fill various spots in the garden. The following are recommended, and are very frost or cold tolerant given the right conditions:
Cacti and Succulent Plants
Agave utahensis, parryi, harvardiana
Sempervivum and Jovibarba (many varieties and species)
Sedum acre, oreganum, dasyphyllum, spathulifolium, Purple Emperor, spurium Voodoo, rupestre, forsterianum, and many others.
Orostachys spinosa, iwarenge, japonica
Delosperma nubigenum, cooperi, dyeri, congestum, and many named varieties (some are tougher than others)
Opuntia humifusa, pheacantha, polyacantha, imbricate, fragilis, (and others)
Escobaria missouriensis, sneedii, vivipara
Echinocereus viridiflorus, coccineus, triglochidiatus
Architectural and Foliage Plants
Yucca filamentosa, glauca, baccata, harrimaniae, nana
Eryngium maritumum, caeruleum, bourgatii, and others
Good for Flowers
Penstemon heterophyllus, barbatus, digitalis, hirsutus, virens, spectabilis, palmeri (many species available)
Crocosmia species, (these need some moisture during the summer months)
Thymus (various Thyme species)
Rosmarinus officinalis (Rosemary)
Gladiolus tristis (with shelter), also Gladiolus papilio, illyricus and some others.
Salvia (many species)
Agastache species (and Hybrids), aurantiaca, neomexicana
Lewisia cotyledon, longipetala, rediviva
Trachycarpus fortunei, wagnerianus
Eschscholtzia californica (Californian Poppy)
Fouqueria splendens (with shelter from wet in winter)
Many plants are well adapted to thrive in harsh environments – seemly cheating death by surviving deep snow cover for months, extreme heat, extreme wet or extreme drought. It will come as no great surprise that many of the plants that thrive in dry environments are also adapted to conditions which are relatively warm, originating in desert habitats which are baked dry during the day and withstanding surprisingly cold temperatures for brief periods during the night.
Rainfall can be a brief event in these habitats, and the plant life is usually quick to make the best possible use of any water available – and in these events we can see a sharp division between the ‘sprinters’ and the ‘marathon runners’.
The ‘sprinters’ are the quick to flower annual plants which germinate from seeds and finish flowering within a few short weeks or months before dying and scattering their seed far and wide – waiting for the next opportunity to grow.
The ‘marathon runners’ are adapted for long-term survival, by being prudent with how they use their resources and often by storing excess moisture in underground roots or tubers, swollen stems or succulent foliage. The marathon runners tend to be more concerned with producing good quality seed at the right time, and can also possess a degree of seed dormancy which can make propagation a challenge.
In many cases the rainfall is highly seasonal, occurring in a brief period between winter and summer both of which are likely to remain reasonably dry in ‘Xeric’ areas.
With careful design and well-chosen plants it should be possible to create a landscape which both saves water and looks beautiful.