Eight Components of Water Neutral Gardens (WNG)
Selecting plants that require little water or none at all is an easy way to build water neutral gardens. California native plants are accustomed to being sustained with little rainfall. Consequently, through the use of native plants, it is possible to create water neutral gardens which only use irrigation for plant establishment. It is essential to understand your site. Where do you live? By the ocean, inland, or in the mountains? There are multiple plant communities in California; the starting place is to know what was originally growing in your area. For example, I live in an area that is near the coast and was once grassland so there are the Coastal Scrub and Bluff Communities. My plant selections, therefore, could be from these groups.
There has been much written on this topic and I would encourage you to read and browse these wonderful resources: California Native Plant Society, California Native Garden Foundation, and a Yahoo Group: Gardening with Natives.
In addition to considering natives, we could also select plants that are accustomed to growing in the climate zones in which we live. For example, I live in a Mediterranean climate and have selected plants that do well in rainy winters and dry summer (northern hemisphere).
Fruit and nut trees as well as vegetables can be an integral part of Water Neutral Gardens, and rainwater can be used for these edible portions of your property.
2. Soils and Soil Structure and Texture
Soil plays an integral part in the success of water neutral gardens. Do you know what type of soil you have? Time to get out a shovel and dig a hole. The deeper you go, the more information you will find. Were you even able to get your shovel into the soil, or did it bounce off? Need a pick? Sometimes soil that is uncovered will develop a hard crust and you will need this tool. Once you dig about 12 inches, you should be able to make some on-site discoveries. For example, what color is the soil? Usually, the darker the soil, the higher the organic content and this is good news. On the other hand, lighter colored soils like beige, yellow, or red indicate a soil with less organic material and more mineral. Organic materials are important for plant nutrition and health.
Now put some soil in your hand and roll it around. Does it fall apart easily? If so, it is more of a loam or sand variety. If it is sticking to your fingers and holds together when you squeeze it, that means you probably have a clay or clayey loam soil. The soil texture is important information. In most cases, a sandy soil drains quickly, a sandy loam soil, less quickly, in gradients all the way to clay which might drain a little or extremely little. Plants need air (gases) and water to survive and the type of soil texture and structure make a difference. With regard to WNGs, soils with some clay in them help hold water; and, of course, that is what we are looking for, contrary to many people’s opinions about clay.
3. Water Table
Some of this might seem fundamental. I am sure you will skip parts of this that you already know about. Having a high water table can be an advantage when developing Water Neutral Gardens. I recommend checking out this survey for information about your soils. There are simple instructions on how to zoom in on your property and discover what is really making your garden tick. So when you know your water table, you can understand that “impermeable surface at 80” will have a positive effect on your plants, if managed correctly. During a dry season, trees, shrubs, and even grasses can tap into this subsurface source to maintain optimal plant growth. Many older trees and shrubs have already done this and need little water. So find out about your soils and save a lot of money and time.
4. Greywater (manual, gravity, and pumping)
My municipal water department sends 2.8 million gallons of potential greywater to the sewage treatment plant each day (39% of total “waste water).. This water could be used in our gardens that currently use between 30% and 50% of our total purified drinking water supply for their needs. Using potable water for our lawns ornamentals, and vegetables is a practice we need to change when so much greywater water is available. Note: it does use a lot of energy (30% in CA) to pump and purify our drinking water. In addition to this, we have over-drafted our aquifers and have even considered building desalinization plants to remove the salt from water, with damage to the environment and even more energy use. You can start to use greywater in your home right now.
Here are some options. First, and most simply perhaps, put a bucket in your shower to receive the cold water that precedes your warm water. Then, if you are a vegan like I am, you can use the wash water from your kitchen sink to water your plants. In addition, you can hook up your washing machine to a pipe to water your garden. I currently water about 1/3 of my garden with water from my washing machine.
This type of system is permit-exempt and we can help you DIY or install a complete system ($500-$1,800 for a complete system installation).
I also have an outdoor shower (cold water from the garden spigot) that I clean up in every morning after a soak in my hot tub. This is another simple, low-tech method. Of course, you can take it a step further, by installing a branched drain system from your shower, bath, and bathroom sinks (see www.oasisdesign.net for complete plans and instructions).
Finally, the Cadillac of greywater systems is the Aqua2use system that can transform your entire garden (sans lawns) into a WNG. It has the capability to water entire gardens using your shower/bathtubs, bathroom sinks, and washing machine. Most houses with slab foundations have their plumbing encased in concrete, making it difficult to plumb this type of system. This system can cost between $3,500 – $4,000, depending on the size of your garden. It is a permitted system that requires a complete design submitted for approval to the Environmental Health and Building Departments. Permit fees are included in the prices stated.
5. Rainwater (passive and active)
One of the most reasonable ways to water your garden is with the free water from your roof. Running the downspouts into areas of your garden can reduce the need for summer watering for at least 30 days and possibly more depending on the amount of recent rainfall. There are a few ways to do this. One is creating infiltration basins for the water to collect in. This is a basin up to 18” in depth made around trees and shrubs to collect water during the rainy season. Additionally, rainwater harvesting systems utilizing rain barrels or large tanks are also common and effective. With many different possible systems, rainwater harvesting can be applied in all water neutral gardens.
This is probably one of the easiest ways to reduce water use when creating water neutral gardens. It also takes care of additional important things in your garden like weed control and nourishing of your plants.
I like to sheet mulch with cardboard from bike and appliance stores (larger sheets) or even from your grocery store (smaller pieces for around plants). Laying the cardboard around your plants and covering it with 2 – 4” of wood chips from your local tree company slows evaporation of soil moisture and keeps the soil evenly moist.
It is also one of the best ways to eliminate existing and future weeds. Earthworms and billions of micro-organisms love this environment and help develop humus as the cardboard and wood chips break down. These helpers also gobble weeds and weed seeds. It is wonderful to know that this natural process is taking place instead of herbicides that actually kill micro-organisms and create what I call “dead” soil–soil lacking the abundant life of these organisms. These organisms also are key players in the transfer of nutrients from the soil. Carbohydrates developed by the plant through photosynthesis are exchanged for soil nutrients that have been made more available for absorption by micro-organisms. Scientists have discovered that this is one of the most efficient ways to nourish plants. Because of this process, the plants are able to withstand drought stresses.
In addition to sheet mulching, there are numerous other ways you can mulch your garden. Spreading a 2-3” layer of mushroom compost over all your planter beds will surprise you. This compost, available at most landscape supply centers, is reasonably priced and will provide your plants with nitrogen and other important nutrients. Most importantly, it is inoculated with beneficial mycellium that again will biologically activate your plant and the soil surrounding it. It also looks good around your plants by creating a uniform color and texture. Note: it smells like a farm for a few days.
Firbark, redwood mulch, and cedar wood chips are other options that can be expensive. Avoid “Gorilla Bark” (redwood bark shavings), because it is hydrophobic (repels water). This will prevent the penetration of water by rain or sprinklers. It does a good job of keeping the soil dry around the plants, something we want to avoid.
7. Water Management techniques (monitoring individual situations)
Once you have considered the condition of your soil, selected the right plants, set up your watering systems, and have everything well mulched, you will still need to monitor the ongoing water needs of your plants. Walk through your garden regularly and observe your plants for signs of over- or under-watering. Clean out your greywater mulch basins as necessary, and make adjustments to emitters to make sure your water is flowing according to the needs of your plants.
8. Understanding shade and sun (different zones)
In designing your water neutral garden and maintaining it over time, be sure to give considerations to patterns of sun and shade. Water evaporates more slowly from areas where there is shade or partial shade, so less water can be applied to these areas.
To learn more about water neutral gardens, review this Design and Build Water Neutral Landscape Presentation.