Saving Water in the Garden - Xeriscaping
Water in the form of rain and snow is scarce in some areas of British Columbia. Areas of the Okanagan, Thompson, Similkameen and East Kootenay valleys receive less than 400 mm (15 3/4”) of precipitation a year, compared to Vancouver which receives at least 1,250 mm (50”) a year.
These same valleys also have the hottest summer temperatures in BC. As a result of this and other climatic and soil factors, the natural vegetation that grows here has evolved to survive drought conditions. These dry valleys are picturesque with expanses of golden grasslands and the occasional Ponderosa pine tree. They are quite different from the temperate rainforests of the coast but just as full of biological diversity.
Living in these desert-like valleys allows residents to grow some amazing gardens. However, the price is high water use. According to research compiled by the Design Centre for Sustainability at UBC for the town of Oliver, lawn and landscape irrigation can represent 50 to 70 per cent of domestic water use.
Xeriscaping is a landscaping technique that significantly reduces water consumption while beautifying gardens and reducing maintenance. Xeriscaping involves seven basic principles: planning your landscape, the selection of plants with minimal water requirements, minimizing the amount of turf area, the use of soil amendments such as compost, the use of mulch, and efficient irrigation and maintenance practices.
Xeriscape can also be applied to other areas of BC, even on the west coast. You might live in an area which experiences several weeks of drought in summer or live on a south-facing slope where it gets very sunny and hot. With climate change, these hot and dry areas will become more prevalent and will benefit from water conservation.
Designing a Waterwise Garden
Your yard is an extension of your home. Imagine it’s your outdoor living room. Get creative and have fun re-designing it with water conservation in mind.
Start by drawing a base map including the lot line, the buildings, patios or decks, telephone poles, septic fields, utility meters, heat pumps, and any other feature that will remain. Be aware of how the rainfall or irrigation would flow. What is the slope, where are the depressions, and possible water run-off paths? Indicate any natural features such as creeks or existing vegetation you intend to keep. Lastly, draw the North arrow and wind direction.
Consider the following when designing your waterwise outdoor living area:
Where are the sunny and shady areas? Frost pockets, windy areas? Where are your movement corridors (walkways, driveway, paths, etc.)? What do you use your outdoor area for (play areas, entertaining, BBQing, pets, sports, growing food, etc.)? Are there views or noise you want to keep or block out? Any wildlife you wish to attract (birds, beneficial insects) or deter (rattlesnakes, bears, etc.)?
To cut down on your water use, design your outdoor living area by water zones. Group plants with similar water and sunlight needs. This will also help to better design your irrigation system. For instance, Zone 1 can include the vegetable garden, fruit trees, the lawn, and thirsty ornamentals. This becomes like an oasis in the grasslands as it gets a lot of supplemental irrigation. It is common to locate this zone closest to your home.
As you move further away, create zones with less water need. Zone 2 houses the plants that require low amounts of water, perhaps with micro or drip irrigation.
The driest zone is Zone 3 and is home to plants that do not require any irrigation once they are established. This is the zone where native plants and drought-tolerant ornamentals thrive. It can look very manicured or it can be wild and natural. It can also be a natural grassland, wetland, rocky slope, or whatever natural ecosystem you live within. If you live on a large lot or a farm, make Zone 3 your largest zone in order to save the most water.
Turf is Out
Lawns, the beloved well-manicured expanses of green grass that our culture has held on to from the colonial past, are costly to maintain – on the pocketbook, on your yard time, and on the environment (water use, fuel or electricity to run the mower and trimmer, air and noise pollution, pesticides and fertilizers).
Reducing the amount of conventional Kentucky Bluegrass lawn in your landscape is the single, most effective way to save water. As you redesign your landscape, ask yourself, “How much turf do I really need? How do I use it?” Most importantly ask, “Can I reduce its square footage?”
If you don’t really use the lawn, don’t be afraid to get rid of all of it. Get creative with a mix of drought tolerant plants and alternative ground cover like permeable bricks, wood mulch, or gravels. There are plenty of green and silvery ground covers that use less water: woolly thyme, kinnikinnick, or creeping junipers to name a few.
For those who love the look of the lawn and can’t bear to do without it, try reseeding or overseeding the thirsty Kentucky Bluegrass with other more drought tolerant grass mixes available at some garden centres. These can be fescues (‘Eco-Lawn’ or ‘Enviroturf’ brands), buffalo grass, or a buffalo grass/blue grama grass combination. Low-water alternatives can be mowed or left to grow tall, forming a meadow.
Choosing Drought-Tolerant Plants
Xeriscaping uses drought-tolerant plants that thrive without supplemental irrigation. However, even these hardy plants need irrigation for the first two years after transplanting or until their roots are well established.
Depending on where you live in BC, different plants will successfully grow without supplemental water. Native plants often do best. If you do not live in an arid area, look for native plants that grow on dry, south facing slopes.
Native plants have many benefits: a) they provide food and shelter for wildlife, b) they are adapted to your region so use very little water, if planted in an appropriate location, c) they are low-maintenance, d) they are beautiful, unique, and there are many to choose from.
To learn about native plants visit your local nursery and ask if they carry any, or ask if there are any local nurseries that specialize in propagating native plants. If you like exploring nature, take a walk in a nearby provincial park or protected area with a plant book, and start identifying and learning about the unique native plants that grow there. Remember not to pull plants out of the ground from their native surroundings. Get them from a plant nursery that specializes in propagating them, or salvage native plants (with permission) from lands scheduled for development.
Appropriate soil preparation is important when planting a waterwise garden. As a general rule, most drought-tolerant plants tend to thrive in well-drained soils with a neutral or slightly alkaline pH, and low to medium fertility. So, amend your soil accordingly.
Take a walk in the grasslands or the forests and you will notice that nobody is raking up the ground. Leaves, pine needles, dead grass, and other organic matter blanket the soil, thus reducing evaporation, preventing weed seeds from sprouting, and adding nutrients.
The summer sun can heat up exposed soil considerably, sometimes harming plants. A layer of organic material helps to moderate the soil temperatures and also prevents the soil from drying up and crusting. As gardeners we try to mimic nature by adding a blanket to the soil; we call it mulch.
Organic mulches can be material like shredded leaves, straw, compost, pine needles, bark chips or chipper debris, saw dust, shredded bark, grass clippings, and manures. The recommended depth is two inches for fine mulch to four inches for rough mulch. Check the depth once a year, and supplement with additional mulch as needed.
Remember not to bury stems or trunks of trees, shrubs, or woody perennials as this increases pest and fungal problems. Some mulches can be flammable, so it is important to place them away from wooden walls and fences.
Some plants, like cacti, succulents, and artemesias, do not like mulch, as too much moisture makes them rot.
Inorganic mulches are non-living materials like black polyethylene plastic, landscape cloth, white plastic, or different rocks and gravels. They last a long time and are great for high traffic areas like pathways.
If you opt for a rock garden and use rock mulch keep in mind that the sun will heat them up. Even drought tolerant plants will be stressed by the increased temperatures and they will need to be watered more often, so this doesn’t end up saving on the water bill. They also heat up the ambient air so your air conditioning bill might go up too.
Rock features have their place though, and they do look stunning when used as part of a garden. So with common sense and creativity, there is always a good spot for the inorganic.
Saving Water Drip by Drip
Xeriscaping aims to conserve water by implementing an efficient irrigation design. Group your plants according to their watering and sun exposure requirements, and only water when it is necessary. Generally, this is when the leaves of shrubs and perennials begin to droop, or in the case of a lawn, when you can see your footprints on the grass when you walk on it. If the top inch of soil next to a plant feels dry when you wiggle your finger into it, this is another sign that water is needed.
Use an irrigation system that delivers water directly to the soil within the root zone of the plants needing water. Low flow systems, such as “micro” or “drip” irrigation are very efficient. This system includes a flexible supply tube that lays on the soil surface, with individual emitters that supply each plant. Gardeners can consult with local irrigation suppliers for information before starting a project.
For many garden areas, complex irrigation is not necessary, and hand-watering or moving sprinklers will suffice. This is especially the case for the dry or natural zone which will not require regular irrigation once the plants are established.
Xeriscape is not zeroscape. Even rock and gravel landscapes need to be cleaned to keep the organic matter from building up and weeded once every couple of years. A drought tolerant plant garden can be low-maintenance though. The main things to keep on top of are: weeding (but mulching helps reduce it), pruning (e.g., cut out dead, diseased and damaged limbs), and topping up the mulch when necessary. Most xeriscape plants do not require fertilizer or irrigation once established.
Paula Rodriguez de la Vega is an ecologist living in Oliver working on habitat restoration, species at risk stewardship, xeriscaping, and local food initiatives.
Durance, Eva. Cultivating the Wild; Gardening with Native Plants of BC’s Southern Interior and Eastern Washington. Nature Guides BC, 2009.
Rodriguez de la Vega, Paula. Waterwise Gardening for Home and Small Acreage Owners of the Oliver Area, 2011. Download free from Town of Oliver at http://oliver.fileprosite.com/Documents/DocumentList.aspx?ID=28370
Okanagan Xeriscape Association, http://okanaganxeriscape.org
Naturescape BC has a series of books on gardening with native plants. Ph: 1-800-387-9853 to order.
Habitat Acquisitions Trust, Gardening with Nature, www.hat.bc.ca
[From WS Summer, 2012]
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