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Take a Soil Percolation Test

In the San Diego region, rainfall can be unreliable and insufficient to sustain landscaping without careful planning and a little help. An alternate water source, such as irrigation, may be required.  

To make choices about the best, most efficient irrigation system for your landscape, it’s important to learn how well your soil drains.  

How does your drainage perform? 

Assessing how well water drains through your soil involves a simple percolation or drainage test. Follow these four steps: 

1) Dig a hole the size of a one-gallon plant, about 12 inches deep and 12 inches wide. 

2) Fill the hole with water and wait. Time how long it takes the hole to drain completely. This is needed to saturate the soil. 

3) Once the water has drained and none is visible in the hole, fill the hole with water again.  

4) Lay a stick or a shovel handle across the top of the hole, and measure the distance from the top of the hole at the handle or stick to the top of the water once every hour until it drains completely the second time. You may want to set a timer so you don’t forget to make your measurements. 

Percolation and soil quality 

If your soil drains more than four inches per hour: You have sandy soil. You need to add organic matter to improve the soil.

If your soil drains less than one inch per hour: Your soil needs extra help to drain. Try sheet mulching (link to page 19) 

If your soil drains from one to four inches per hour: Good news, your soil is a sponge and drains well. This is the goal.    

It isn’t difficult to build healthy, well-draining soil. Get our tips on how to create health soil here.

 

This article was inspired by the 71-page Sustainable Landscapes Program guidebook available at SustainableLandscapesSD.org. The Water Authority and its partners also offer other great resources for landscaping upgrades, including free WaterSmart classes at WaterSmartSD.org. 

 

 

 

Capture as much rainfall runoff as you can and put it to use as landscape irrigation. Photo: StevePB/Creative Commons rainfall as resoure

Rainwater as a Resource for Your Landscaping

During the rainy season, runoff from hard surfaces around the home such as roofs and patios can be directed to the permeable landscaping. By capturing as much rainwater as possible in the soil, it is possible to build an ecosystem that can last through the summer months with minimal additional irrigation.  

The entire built environment can be re-imagined and transformed into a living sponge. If more rain falls than can be absorbed, or if the soil is particularly impermeable, rainwater can be directed through landscaped areas to remove pollutants before it flows downstream. 

Adjusting systems to maximize rainwater capture

There are three basic steps to capturing rainwater. First, check your roof to determine where precipitation is directed after it hits the surface — whether into rain gutters, off the edge, or elsewhere. Second, choose how and where to hold excess rainwater based on this assessment. Last, consider making upgrades such as adding rain barrels or making changes in your landscaping. For instance, landscaping soil may need amendments to hold more water. 

Is your soil more like a brick or a sponge? 

If your soil is more like a brick, it will affect how landscaping is contoured to capture water. Adding soil amendments will help it become more like a sponge that retains water for drier weeks and month. If the soil doesn’t drain well, take special care to avoid drowning new plants. 

When choosing landscaping plants, match them to the soil type. If the soil is sandy, look for plants with “dry feet” that prefer free-draining soil, If the soil is harder clay, look for plants that do not mind heavy soil.

Optimal landscape soil can capture rainwater and allow it to soak in completely in 24 to 48 hours.  

Many homeowners also use rain barrels to capture rainfall before it reaches the ground so it can be released during dry times. For more information about rain barrels, go to WaterSmartSD.org for information about purchase, rebates, and a one-minute video guide to installation.

 

This article was inspired by the 71-page Sustainable Landscapes Program guidebook available at SustainableLandscapesSD.org. The Water Authority and its partners also offer other great resources for landscaping upgrades, including free WaterSmart classes at WaterSmartSD.org. 

 

 

You can't always tell by looking at your plants whether you are overwatering or underwatering. Photo: Water Authority

Does Your Landscaping Need Water?

Before adding irrigation to landscaping, make sure it’s needed. Appearances can be misleading, and cause water to be used unnecessarily. 

First, use “digital” technology. Because soil may appear dry on the surface, stick your finger into the soil and see if the soil is wet beneath the surface. If the soil is moist up to your second knuckle, it doesn’t need any more water. Wait for another 24 to 48 hours, and check the soil again. 

As an alternative, use a soil probe and measure the moisture in the soil to determine whether the soil needs more water.  

Another strategy is to assess plant health. How vibrant are they? This can be tricky, because sometimes the signs of overwatering and underwatering will produce similar results in plants.  

Underwatering symptoms include: 

  • Soil is bone dry 
  • Older leaves turn yellow or brown, and drop off 
  • Leaves are wilted 
  • Leaves curl and become brittle 
  • Stunted plant growth

Overwatering symptoms include: 

  • Soil is constantly saturated and soggy 
  • Leaves turn a lighter shade of green, or turn yellow 
  • Younger plant shoots wilt 
  • Leaves are green and brittle 
  • Algae and mushrooms are in the soil 
  • Growth is excessive 

Since the symptoms at both extremes can be similar, it’s best to rely on objective measurements rather than observations. Using simple measurement tools can help ensure the correct amount of irrigation takes place without withholding needed moisture, but without overwatering and wasting resources.  

 

This article was inspired by the 71-page Sustainable Landscapes Program guidebook available at SustainableLandscapesSD.org. The Water Authority and its partners also offer other great resources for landscaping upgrades, including free WaterSmart classes at WaterSmartSD.org. 

 

 

Maximize your landscaping soil's ability to retain and save rainfall and irrigation for drier days. Photo: D. Douk/Creative Commons

Building a Water Savings Account

Managing water wisely in a landscape is a lot like managing a bank savings account.  

Approximately half of the water spent by average California homes is used outdoors, mostly for irrigation. Unfortunately, up to half of commercial and residential irrigation water is squandered by evaporation, wind, improper system design, or overwatering, according to the U.S. Environmental Protection Agency.  

Using landscape irrigation efficiently can significantly reduce overall household water consumption while leaving adequate water in the ground to cover your plants’ needs. 

During the winter in metropolitan San Diego County, healthy soil can absorb water in surprisingly large quantities to be released slowly to plants as they use it during drier months – like using a savings account to pay for expenses over time.  

That’s particularly true during wet spells like we’ve had in late November and early December 2018; no need to spend irrigation water when Mother Nature is making the deposits for you. 

Balance your water bank account 

Water that enters the soil as rain or irrigation is like a deposit into a soil checking account.  

By keeping track of those transactions of water in and water out, it is possible to know how much water in the soil “reservoir” is available in the landscape at any given time for the plants to access. 

The initial soil bank balance is determined by direct observation or is assessed after a thorough wetting of the soil by irrigation or winter rains. Every day, plants take small amounts of water from the soil. Rain and irrigation fill up the water bank again. The trick is to make sure this “account” does not get overdrawn. 

How can you tell when the account is depleted? Smart irrigation controllers and landscape professionals can calculate this for you. You can also rely on a soil probe, or even testing the landscape by feeling the soil surface with your fingers. 

 

When oxygen and water are balanced in the soil, the amount of water lost through evapotranspiration is similar to paying fees on your savings account. Shading the soil surface with plant materials and mulch protects water in the soil by slowing evapotranspiration and leaving more water in your soil’s account. 

 This article was inspired by the 71-page Sustainable Landscapes Program guidebook available at SustainableLandscapesSD.org. The Water Authority and its partners also offer other great resources for landscaping upgrades, including free WaterSmart classes at WaterSmartSD.org. 

 

 

Give new landscaping plants plenty of room to grow and thrive. Photo: Water Authority

Give New Landscape Plants Space To Grow

When choosing plants for new sustainable landscapes, it’s important to account for the height and the width of each plant species when it matures. This allows you to properly space plants in the landscape without having them feel crowded.  

Proper plant placement, taking into account the mature plant’s size, also should limit the need for future pruning, and reduce the amount of maintenance required in the long run. 

Natural plant shapes and sizes maximize habitat value, but wildfire prevention requires regular pruning and removal of dead plant materials.  

The spacing chart below helps to judge how many plants are needed per square foot, based on the mature size of the plants.  

Space plants on your landscaping plan at their full mature size, not the size when you first plant them. Graphic: Water Authority

Space plants on your landscaping plan at their full mature size, not the size when you first plant them. Graphic: Water Authority

Scale your plants at maturity 

On your landscaping plan, use circles to note the size of every plant at maturity using a scale in which one inch equals four feet. Use colored pencils to note different water needs of the plants selected. It will make it easier to group plants into their proper irrigation zones (hydrozones).

Wide canopy trees that grow to 20 or 30 feet in diameter will significantly change the landscaping over time. Consider whether a tree will cover a large section of landscaping with shade that is currently getting full sun. If plants that thrive in full sun are eventually covered in shade, the landscaping may need to be revised in the future.  

Small but mighty 

Select the smallest, healthiest plants possible, especially when choosing native plants. Once they are planted in properly prepared soil and watered wisely, small plants establish themselves more vigorously than plants raised in larger containers. Do not plant more than the space allows when the plants mature. 

Root depth matters 

Take note of the root depth of plants when they are placed into the landscaping. Note root depths on your landscape plan. Trees will be irrigated less frequently, but for a longer period of time. Groundcovers with shallower roots require more frequent, shorter periods of irrigation. Keep these types of plants in separate hydrozones 

 

This article was inspired by the 71-page Sustainable Landscapes Program guidebook available at SustainableLandscapesSD.org. The Water Authority and its partners also offer other great resources for landscaping upgrades, including free WaterSmart classes at WaterSmartSD.org.    

 

 

  

Mirroring Native Plant Communities in Sustainable Landscaping

In nature, plants arrange themselves into communities of “friends” based on common microclimates, water and nutrient needs, and how they interact with the physical environment. Native plant communities also are based on interactions with each other and other species such as insects, birds, and other animals.

Most plant communities occur repeatedly in natural landscapes under similar conditions.

Local native plant communities have evolved together over a long period of time, and grow well together. They will even “reject” the outsiders and work together to compete for nutrients, sunlight, and other resources

This is one of many good reasons to learn about the San Diego region’s native plant communities and to select plants that like to live together in communities for sustainable landscaping.

Three examples of San Diego regional plant communities

California Coastal Prairie Community

California Coastal Prairie along the coast north of Jenner, California. Photo: Wikimedia/Creative Commons

California’s coastal prairies are the most diverse of any grassland in North America. Perennial flowers outnumber grass species here. Plants include: California Poppy (Eschscholzia californica), Blue-Eyed Grass (Sisyrinchium), Fern Leaf Yarrow (Achillea ‘Moonshine’), Seaside Daisy (Erigeron glaucus), and Cliff Buckwheat (Eriogonum parvifolium)

California Coastal Sage Scrub Community

California Coastal Sage Scrub in the San Pasqual area. Photo: Barbara Kus, USGS/Creative Commons

California Coastal Sage Scrub in the San Pasqual area. Photo: Barbara Kus, USGS/Creative Commons

California coastal sage scrub features fire-adapted, drought deciduous plants, which are rapidly disappearing to urbanization in southern California. Fortunately, some areas, including the San Diego Safari Park Biodiversity Reserve, have been conserved. Plants include: grey musk sage (Salvia Pozo Blue), sticky monkeyflower (Diplacus aurantiaus), San Diego sage (salvia munzia), fuschia gooseberry (Ribes speciosum), and woolly bluecurls (Trichostema lanatum)

California Chaparral Community

California Chaparral near the University of California, San Diego. Photo: UCSD/Creative Commons

Chaparral exists in many coastal ranges, and on the western and eastern slopes of the southern California mountains. It is ‘hard’ brush that doesn’t rely as much on summer fog as the Coastal Sage Scrub does, and it is adapted to heat and drought. Plants include desert mallow (Sphaeralcea ambigua), bent grass (Agorstis pailens), San Diego mountain mahogany (Cercocarpus minutiflorus), bush poppy (Dendromeconi riguda), and clumping wild rye (Leymus condensatus),

 

This article was inspired by the 71-page Sustainable Landscapes Program guidebook available at SustainableLandscapesSD.org. The Water Authority and its partners also offer other great resources for landscaping upgrades, including free WaterSmart classes at WaterSmartSD.org.

 

 

Everett’s California Fuchhia is an example of a plant that doesn't like to have wet feet, meaning roots sitting in water. Photo: Wikimedia Commons

Plants With Wet Feet and Dry Feet

Plants and people have similar likes and dislikes when it comes to their feet.  

Of course, plants don’t literally have the kind of feet that take them on a stroll, but a plant’s roots are often referred to as “feet.” Just like most people enjoy a walk along the beach or wading in a pool on a hot day, plants like – and need – water on their roots to thrive.  

And just like people don’t like soggy feet in wet socks, plants don’t generally thrive with their roots in standing water. Horticulturists refer to plant roots in soggy soil as “wet feet.” Conversely, plants that can thrive without much water on their roots are said to have “dry feet.”

Excessive moisture at the roots can cause rot and other diseases; very few plants grow in wet areas. While that isn’t a common problem in the arid Southwest, plants can end up in standing water in poorly drained (or over-irrigated) areas of landscaping.  

That means it’s important to match landscaping plants to the environment of their feet.  

Five recommended plants compatible with wet feet 

The California Native Iris (Iris douglasiaria) is a plant that doesn't mind having "wet feet," or damp roots. Photo: Wikimedia Commons wet feet

The California Native Iris (Iris douglasiaria) is a plant that doesn’t mind having “wet feet,” or damp roots. Photo: Wikimedia Commons

  • Coyote Mint (Mondarella villosa) 
  • California Gray Rush (Junous patens) 
  • Joaquin Sunflower (Bidena laevis) 
  • Deer Grass (Muhlenbergia rigens) 
  • California Native Iris (Iris douglasiaria) 

Five recommended plants incompatible with wet feet  

Everett’s California Fuchhia is an example of a plant that doesn't like to have wet feet, meaning roots sitting in water. Photo: Wikimedia Commons

Everett’s California Fuchhia is an example of a plant that doesn’t like to have wet feet, meaning roots sitting in water. Photo: Wikimedia Commons

  • Bluff California Lilac (Ceanothus maritmus) 
  • Everett’s California Fuschia (Epilobium canum) 
  • Sunset Manzanita (Arctostaphylos Sunset) 
  • Hairy Awn Muhly (Muhlerbergia capillans) 
  • Blonde Ambition Blue Grama (Boutelous gracilis)

Get advice from the local garden center or horticulturalists familiar with your area for other good choices.   

 

This article was inspired by the 71-page Sustainable Landscapes Program guidebook available at SustainableLandscapesSD.org. The Water Authority and its partners also offer other great resources for landscaping upgrades, including free WaterSmart classes at WaterSmartSD.org.    

 

 

  

Your plant choices should be governed by the individual hydrozones in your landscaping. Photo: Kelly M. Grow/ California Department of Water Resources

Playing by the Hydrozone Landscaping Rules

Hydrozones are the different areas of your landscape with different irrigation needs. These needs can vary greatly in a single yard. By managing your water distribution to meet the needs of each hydrozone, you can minimize water waste and promote healthy plants.

For example, plants with similar growing requirements including water needs should be planned and planted together so water can be applied as efficiently as possible through rainwater catchment, supplemented by irrigation. 

The amount of sunlight and shade, temperature differences, soil conditions, slopes, and plant root depth should be considered, along with plant water needs, to create hydrozones. Even when the soil is the same, a full sun area is one hydrozone, full shade areas are another, and mixed exposure areas create yet a third zone.  

Within your irrigation system, each individual irrigation valve should water a separate hydrozone populated by plants with similar water needs, living conditions, and root depths. Plants with high water needs such as vegetables or lawns must be on their own hydrozone. Sprinklers or emitters on this zone shouldn’t water anything else, including hardscape areas such as sidewalks.  

Don’t overdo it with irrigation 

 Each hydrozone should have sprinklers or emitters generating the same amount of water, and they should be spaced out so that every plant in the zone gets the same amount of water. If the spray of two sprinklers overlap, plants receiving water from both will receive much more water than they need. In cases like this, sprinklers should be turned away from each other, or placed farther apart. Professional landscapers call this “matched precipitation.”   

This article was inspired by the 71-page Sustainable Landscapes Program guidebook available at SustainableLandscapesSD.org. The Water Authority and its partners also offer other great resources for landscaping upgrades, including free WaterSmart classes at WaterSmartSD.org.

Match your plant choices to the different microclimate areas in your landscaping. A microclimate map helps you make good choices. Photo: Water Authority

Match Your Landscape Plants To Your Microclimates

A previous Conservation Corner article explained how to map the different types of microclimates present in your landscaping. This information can help homeowners effectively arrange plants in their sustainable landscapes. For the most efficient water use, plants should be grouped together with similar water needs in their favorite microclimate.  

In nature, plants that like lots of water are found along the banks of streams, or grouped together at the base of landscape depressions. Plants that need fast-draining soils so roots don’t rot might be found on hillsides. Plants that love lots of sunshine won’t grow in the shade of a tree.  

Follow the microclimate map  

Look to the Microclimate Map for guidelines on choosing landscape plants. Here is a hypothetical yard with three microclimates:  

  • A front yard in full sun most of the day. 
  • A moist, low-lying area in full sun. (This area will retain moisture more than the rest of the yard, so you may want to use it for rain catchment. Hillside areas surrounding the depression are raised slightly, and drain freely.) 
  • A slightly shady area under the canopy of a neighbor’s large tree, and another one near the front entry to the house. 

Three distinct plant communities 

Selecting plants for the yard in this example will require at least three different groupings:  

  • Sun-loving plants that like their roots dry and thrive in faster-draining soil
  • Sun-loving plants that can tolerate “wet feet” in winter months, and thrive in heavier clay soils
  • Plants that can tolerate dry, shaded areas 

There is another consideration before heading to the local nursery or garden center: How will these plants be irrigated? Check the Plant Factors for each of the plants to make sure their water needs are all similar in each area. Read this previous Conservation Corner story for information about Plant Factors

Plants speak Latin 

Low water use plants and succulents

Many plants have similar names. Rely on their Latin names to ensure you are getting the correct plant for your landscaping plan. Photo: Water Authority

Many plants have similar common names in English. Shopping for plants by their common names can lead to confusion between two very different plants. Instead, the best way to shop for plants is to use the Latin name. This reduces surprises in your landscaping.  

 

This article was inspired by the 71-page Sustainable Landscapes Program guidebook available at SustainableLandscapesSD.org. The Water Authority and its partners also offer other great resources for landscaping upgrades, including free WaterSmart classes at WaterSmartSD.org.    

 

 

  

Different areas of your landscaping are affected by shade, moisture, and temperature, creating a variety of microclimates. Photo: Water Authority

Map Your Microclimates

Every garden has areas where plants flourish, and other areas where plants struggle. Structures, walls, fences and other plants can affect the amount of sun and shade in a garden. Every garden is completely different, even if it is located in the same general climate zone. 

There may be hills and hollows in your front yard that collect cold air. Or, if your property is sloped, you may not get frost when your neighbors do.  

The first step to a new or renovated landscape is walking around your property during the day and observing it closely.  

Which plants are keepers? 

Decide which plants work and which should be removed. Outline the canopy area of the plants being retained. Note the name, general size, and health of the plants. Which are more drought-tolerant? Many plants can thrive on less water when they are well established, with deep healthy roots. Old rose bushes and large shade trees are two good examples.  

Note sun and shade 

Areas of your landscaping under large shade trees become individual microclimates. Photo: Ken Lund/Creative Commons License

Areas of your landscaping under large shade trees become individual microclimates. Photo: Ken Lund/Creative Commons License

Mark the areas that receive sun all day, and areas that are shaded all or part of the day. Also note which areas receive only partial sun, or a few hours of direct morning sun, midday sun, or late afternoon sun. In choosing landscape plants, select those that are appropriate for the sunlight patterns of the garden. Plants marked as “full sun” will not be happy in full shade, and vice versa.  

Group plants for similar needs 

When selecting and grouping plants, note the water requirements of each plant. Make sure plants with different water needs are not placed together. Some sun-loving plants have moderate water needs, and some have very low water needs. If these are mixed together, one will always suffer if the watering routine works for the other types. 

 

This article was inspired by the 71-page Sustainable Landscapes Program guidebook available at SustainableLandscapesSD.org. The Water Authority and its partners also offer other great resources for landscaping upgrades, including free WaterSmart classes at WaterSmartSD.org.