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Grouping plants together by water needs by matching microcliimates creates efficient irrigation. Photo: Water Authority

Microclimate Matching in Your Landscaping Plan

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Earlier in our Conservation Corner series, we described how to map the different types of microclimates present in your landscaping. Using this information helps homeowners arrange plants in a new sustainable landscape. For the most efficient water use, plants should be grouped together with similar water needs according to their preferred microclimate.

In nature, plants that like lots of water are found along the banks of a stream, or grouped together at the base of a depression. 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 smart guidelines on choosing landscape plants. Consider this example yard with three identified microclimates:

  • A front yard in full sun most of the day.
  • A moist depressed area in full sun. This area will retain moisture more than the rest of the yard, so you could use this area for rain catchment. Raise hillside areas surrounding the depression and allow them to drain freely.
  • A shady area under the canopy of a neighbor’s large tree.

Three Different Plant Neighborhoods

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

When selecting landscaping plants, the yard in this example will require at least three different groupings of plants.

  • Sun-loving plants that prefer their roots dry and in fast-draining soil
  • Sun-loving plants tolerant of wet feet in winter months, which thrive in heavier clay soils
  • Plants tolerant in dry shaded areas

A final consideration before heading to the local nursery or garden center: how will you irrigate your plants?  Check the Plant Factors for each of the plants to make sure their water needs are all similar in each area. A previous Conservation Corner feature has information about Plant Factors.

Plants Speak Latin

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 any miscommunication and any surprises in your landscaping. 

This article is part of a year-long series 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.

Knowing how to classify your plants by water use characteristics will help you plan your sustainable landscaping. Photo: Water Authority plant factor

Know Your Plant Factor Water Requirements

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Landscaping plants have different water needs. The water requirement of each plant in your landscaping can be determined by gathering information about the plant and then comparing it to the amount of water needed by the cool-season grass growing in your climate zone.

Take a tip from landscaping professionals. They use a resource called the Water Use Classification of Landscape Species to classify plants according to their water requirements, called Plant Factors.

These water requirements divide plant species into four categories: Very Low, Low, Moderate, and High.

When you are selecting plants for your landscaping, use the classification to choose low water use plants for your landscaping. You can also use it to group a handful of higher water use plants together if you want to indulge in a few favorites.

When you have decided on your plant palette and placement, you can now figure out the water use of your entire landscape area. This will help you plan out your artificial irrigation.

Factor in watering requirements

Determine water use before choosing plants for your new sustainable landscaping. Photo: San Diego County Water Authority

Watering needs for landscape plants use a measuring stick based on cool-season turf. It’s because cool-season turf is extremely thirsty.

When you replace turf areas with climate-appropriate plants that use less water and irrigate them with more efficient systems, you can conserve a tremendous amount of water. You don’t need to turn your landscaping into a dry and dusty area to do it.

High Plant Factor: Plants needing 60 to 100 percent of the water needed for a grass lawn (PF of 0.6 – 1.)

Moderate Plant Factor: Plants needing 30 to 60 percent of the water needed for a grass lawn (PF of 0.3 – 0.6)

Low Plant Factor: Plants needing 10 to 30 percent of the water needed for a grass lawn (PF of 0.1 – 0.3)

Very Low Plant Factor: Plants needing 10 percent or less of the water needed for a grass lawn (PF of less than 0.1)

Irrigate More Efficiently By Grouping Plants

According to the San Diego County Water Authority’s Sustainable Landscaping guidebook, plant selections are colored-coded to identify their water needs under this system. It gives you an easy way to group plants by their water requirements in your new landscaping, so you can irrigate them more efficiently.

This article is part of a year-long series inspired by the 71-page Sustainable Landscapes Program guidebook. The Water Authority and its partners also offer other great resources for landscaping upgrades, including free WaterSmart classes at WaterSmartSD.org.

How Much Water Do Plants Need?

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It’s important to assess how much water your outdoor plants need to stay healthy. The heat and humidity in San Diego County is far from over, with the official start of Fall September 23. Irrigation needs are generally highest during these warm months.

Did you know that plants can be classified by their water needs?

Landscaping professionals use a resource called the Water Use Classification of Landscape Species, or WUCOLS, to classify plants according how much water they need to thrive.

It might sound complex, but it’s very useful because it breaks down the water requirements for each type of plant. There are four categories: Very Low, Low, Moderate, and High. These water requirements are also called Plant Factors. They are an important tool for transitioning to a more water-efficient landscape. By knowing exactly how much water your plants need, you can cut down on your water usage while also keeping your plants happy.

Calculating water requirements for outdoor plants

To calculate a Plant Factor, compare the plant’s water use to cool season grass in a given climate zone.

Why is that? Turf is among the thirstiest of all types of plants. When you replace turf areas with climate-appropriate plants with lower water requirements, and irrigate them with more efficient systems, you can greatly increase your water efficiency. You don’t have to turn your landscaping into a dry moonscape to do it.

Plant factors, or PF, categories:

Plant Factor categories from high to low water use. Graphic: Water Authority

High: Plants need from 60 to 100 percent of the water needed for a grass lawn (PF of 0.6 – 1.0)

Moderate: Plants need 30 to 60 percent of the water needed for a grass lawn (PF of 0.3 – 0.6)

Low: Plants need 10 to 30 percent of the water needed for a grass lawn (PF of 0.1 – 0.3)

Very Low: Plants need 10 percent or less of the water needed for a grass lawn (PF of less than 0.1)

Group plants by PF to irrigate more efficiently

In the Water Authority’s Sustainable Landscaping guidebook, plant selections are color-coded to identify their water needs under this system. That approach provides an easy way to group plants by their water requirements in your landscape, so you can irrigate more efficiently.

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.