Water Conservation

In the development and maintenance of a native landscape, water conservation is the driving force behind efficient and aesthetic designs. Plants should be grouped in separate water-use zones according to their water needs and function within a landscape. Monitoring soil moisture to determine when to irrigate is better than using a pre-set schedule. The soil water-holding capacity will vary with soil type, amount of organic matter and climatic conditions.

Supplemental Water Requirements

Seedings

A moist soil profile, prior to planting, will increase seeding success. Watering should be done in frequent, light applications during the first 4 to 6 weeks to ensure good seed germination, emergence, and root development. The use of an organic mulch can reduce the potential fluctuations in surface soil moisture and soil temperature during this critical establishment period.

Transplants

Young transplants require frequent and regular watering until root development can provide the proper shoot to root ratio. Some woody species (oak in particular) spend several years developing an extensive root system before a corresponding increase in above-ground development is realized.

Established Plantings

There are two times during the year it is critical that the rooting zone of a plant be at or near field capacity—fall and early spring. Fall moisture is essential for the health and vigor of the plant as it prepares itself for the winter months. Trees, in particular, should be deep watered in late fall to prepare for possible warm periods during the winter months. As temperatures warm up in the spring there is an urgent need for water to support rapid early growth.

Other Considerations

• South and west exposures require more frequent watering than north or east exposures.
• Sloping landscapes require water to be applied more slowly than flat surfaces to allow adequate infiltration and prevent runoff.
• With severe slopes, establish berms or terraces to hold water and stabilize the slope.
• Avoid using sprinklers that throw a fine mist high in the air.
• Avoid watering during hot, windy, or rainy weather.
• Root lengths vary. Root depth is proportional to top growth. There are exceptions: grass roots are deep; bulb roots are short compared to their top growth.

Water Conservation Strategies

Zoning

Plants should be established in zones to maximize water use efficiency. These zones will also dictate the best irrigation system to be used, e.g., underground sprinkler (high watering zones), drip/trickle (moderate watering zones), or conventional hose (low watering zones).

Shading/Shielding

Plants that require more moisture or prefer shade can be located beneath or on the shady side of larger plants, fences, or buildings. Afternoon sunlight is more intense, so plants to be shaded should be put on the easterly side of large plants or structures.

Mulching/Landscape Fabric

Mulches are used to minimize evaporation, and to reduce weed growth and erosion. Apply mulch directly to the soil surface or over a landscape fabric. Don’t use black plastic unless it’s been perforated; it prevents air and water from reaching plant roots and it reduces beneficial soil organisms.

Organic mulches such as wood chips, peat, sphagnum moss, or grass clippings decompose and improve soil texture, but must be replenished periodically. Apply in a layer 1 to 3 inches deep between plants.

Inorganic mulches such as rocks or gravel rarely need replacement and are good in windy areas. Apply in a layer 2 to 4 inches deep between plants.

Newly seeded areas can be mulched with weed-free hay, straw or composted grass clippings. This will help retain soil moisture, increase site stability (reduce soil and water erosion), and provide more uniform heat at the time of seed germination. Apply mulch in a layer no more than one-half inch deep over the seeded area.

Caution: Rock mulch can serve as a heat sink and also reflect heat to surrounding plants and buildings.

How Much/How Often

The amount of supplemental water applied and the duration of each application depends on several factors:

• amount & type of plant cover
• amount of organic matter
• type of soil (infiltration rate)
• water application method
• soil compaction (bulk density)
• time of day
• weather (evapo-transpiration)
• slope (runoff potential)

The frequency of irrigation is dependent primarily on the moisture requirements of the plants and the water-holding capacity of the soil. Plants should be carefully monitored for signs of moisture stress, i.e., loss of leaf turgidity (drooping), curling of leaf edges, and leaf discoloration.

Drip Emitters

The most efficient use of water is the slow, deliberate metering of water directly to individual plants. Drip systems can be installed under ground or laid across the soil surface. Most drip systems work with low pressure and often require a filtration system to prevent the clogging of emitters. Drip systems must be monitored to avoid oversaturation below the soil surface.

This information is also available for downloading as Chapter 12 of the publication, Creating Native Landscapes in the Northern Great Plains and Rocky Mountains. This document requires Adobe Acrobat.

Water Conservation (PDF; 1.5 MB)

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