Recycled Water Use in the Landscape

How do recycled water and gray water differ? concern to agricultural crops or ornamental species are Where can they be used? chloride, sodium, bicarbonate, boron, and fluoride. Recycled water is highly treated wastewater from various Appropriate plant selection and good irrigation sources such as domestic sewage, industrial wastewater and management can minimize the potential impacts of the storm water runoff. Most recycled water treatment plants salts or specific ions of concern. produce tertiary treated water, meaning the water has been through three levels of treatment including filtration and Is the same amount of recycled water used as disinfection. Tertiary treated recycled water can be used for potable water when irrigating? landscape, agricultural irrigation, car washing, fish ponds, There is a potential for salt accumulation when using fire fighting, groundwater recharge and in fountains and recycled water. As a result, it may be necessary to slightly recreational lakes where swimming is allowed. Gray water over-water or leach plants irrigated with recycled water. is untreated, non-disinfected wastewater that has not come A general rule of thumb is to allow for a 10% over into contact with toilet waste. Gray water includes watering depending on soil type and plant characteristics. wastewater from residential showers, bath tubs, bathroom Well drained soils and rainwater will help mitigate salt sinks and washing machines which may be used in accumulation effects. landscapes using an onsite collection system and must employ a subsurface irrigation method. Recycled water is cleaner, safer and has far less restrictions on its use than What are the effects on plants? gray water. It does not require an onsite collection system Plants sensitive to salts may be affected mostly by tip and is delivered through a separate plumbing system. Most burning when recycled water with high saline content is recycled water is applied by drip irrigation or conventional applied by spray leaving salts behind when the water sprinkler irrigation. evaporates. Drip irrigation rather than overhead irrigation will minimize foliar injury. Two studies done by By law, all pipes and equipment conveying recycled water University of California at Davis showed low occurrence must be purple or have purple markings as a universal sign of injury to many common landscape plants. In fact, one to prevent cross connection with potable supplies. This study showed health ratings were equal or higher using includes flow control knobs, solenoids, valve boxes, recycled water over potable water in all species tested. In sprinkler heads and of course all piping. In addition, public some cases, nutrient rich recycled water can be beneficial areas must post signs stating “Caution: Recycled Water Do to plant growth and might reduce the need for additional Not Drink”. fertilizers. Summaries of these studies are found in the UCD Department of Environmental Horticulture How good is the quality of recycled water? newsletter “Growing Points” Fall 2001 and Fall/Winter 1996/97 issues available on the internet at: The quality of recycled water depends upon the source http://envhort.ucdavis.edu. water and the level of treatment. Generally recycled water will have a higher concentration of dissolved salts than drinking water. Water with high levels of salts can have What plants can be irrigated with recycled water? adverse effects on plant health and appearance; however, Turf grasses, most annuals, and deciduous trees are more most recycled water produced does not have harmful levels tolerant of saline water than evergreens. Turf grasses of salts for most plants. Irrigation constituents of greatest either have built in tolerance of saline conditions or do not accumulate high levels of salt because of frequent mowing. Deciduous plants don’t accumulate salts in plant tissues because they shed their leaves each fall. A list of plants with high salt tolerance is on the reverse side.

Laws that regulate recycled water:

Water Recycling In Landscaping Act (SB 2095 year 2000): http://www.leginfo.ca.gov/ Health and Safety Code, Water Code: http://www.leginfo.ca.gov/calaw.html Title 17, Division 1, Chapter 5: http://www.calregs.com/default.htm Title 22, Division 4, Chapter3 http://www.calregs.com/default.htm More info: The Department of Water Resources has developed guidelines for the use of gray water in landscapes, available on the Office of Water Use Efficiency Website at: http://www.owue.water.ca.gov/landscape/pubs/pubs.cfm Plants with High Tolerance of Salt in Irrigation Water

Common Name Scientific Name Lemonade Berry * Rhus integrifolia * Agave Agave spp. Leyland Cypress Cupressocyparis X Alkali Sakaton * Sporobolus airoides * leylandi Aloe Aloe spp. Melaleuca Melaleuca spp. Arizona Ash Fraxinus velutina * Mexican Palo Verde Parkinsonia aculeata Modesto Ash* Mexican Pinon Pine Pinus cembroides Beefwood Casuarina stricta Mirror Plant Coprosma spp. Bermuda Grass Cynodon dactylon Myoporum Myoporum parvifolium Bladderpod * Isomeris arborea * Natal Plum Carissa macrocarpa Blue Blossom * Ceanothus thrysiflorus * New Zealand Christmas Metrosideros excelsus Blue Dracaena Cordyline indivisa Tree Blue Palo Verde * Cercidium floridum * Northern Red Oak Quercus rubra Blue Spruce Picea pungens Oleander Nerium oleander Blue Wildrye * Elymus glaucus * Parney Cotoneaster Cotoneaster lacteus Bougainvillea Bougainvillea spectabilis Pindo Palm Butia capitata Breath of Heaven Coleonema spp. Pride of Madeira Echium fatuosum California Brome * Bromus carinatus * Pt. Reyes Ceanothus * Ceanothus gloriosus * California Buckwheat * Eriogonum fasiculatum * Purple Needlegrass * Stipa pulchra * California Fan Palm * Washingtonia filifera * Redolen Acacia Acacia redolens California Fescue * Festuca californica * Rose Iceplant Drosanthemum hispidum California Juniper * Juniperus californica * Rose Moss Portulaca grandiflora California Sycamore * Platanus racemosa * Rosemary Rosmarinus officinalis Callery Pear Pyrus calleryana Saltbush * Atriplex spp. * Canary Island Palm Phoenix canariensis Sandhill Sage * Artemisia pycnocephala * Cape Plumbago Plumbago auriculata Seashore Paspalum Paspalum vaginatum Catalina Cherry * Prunus lyonii * Silk Oak Grevillea robusta Catclaw Acacia * Acacia greggii * Skyrocket Juniper Juniperus virginiana Coast Live Oak * Quercus agrifolia * “Skyrocket” Coffeeberry * Rhamnus californica * Slender Hairgrass Deschampsia elongate Cushion Bush Calocephalus brownii Southern Flannel Bush * Fremontia mexicana * Date Palm Phoenix dactylifera Southern Live Oak Quercus virginiana Deer Grass Muhlenbergia rigens Spanish Bayonet Yucca aloifolia Deodar Cedar Cedrus deodara St. Augustine Grass Stenotaphrum secundatum Dwarf Coyote Brush * Baccharis pilularis * Strawberry Tree Arbutus unedo Dwarf Olive Olea europaea “Montra” Sugar Bush * Rhus ovata * Escallonia Escallonia rubra Texas Ranger Leucophyllum frutescens European Fan Palm Chamaerops humilis Toyon * Heteromeles arbutifolia * Evening Primrose Oenothera Tree Mallow * Lavatera assurgentiflora * speciosa Tree Myrtle Myrtus communis Evergreen Euonymus Euonymus japonica Trident Maple Acer buergerianum Evergreen Pear Pyrus kawakamii Weeping Bottlebrush Callistemon viminalis Feathery Cassia Senna (Cassia) Western Cottonwood * Populus fremontii * artemisioides Western Redbud* Cercis occidentalis * Firethorn Pyracantha coccinea White Ice Plant Delosperma alba Fortnight Lily Dietes irioides Zoysia Grass Zoysia tenuifolia Gazania Gazania spp. Giant Honeysuckle Lonicera hildebrandiana *California Native Gum Trees Eucalyptus sp. Hardtack * Cercocarpus betuloides * Hedge Maple Acer campestre References: Hollyleaf Cherry * Prunus ilicifolia * Abiotic Disorders of Landscape Horsetail Tree Casuarina cunninghamiana Plants: A Diagnostic Guide Indian Hawthorn Rhapiolepis indica University of California, Italian Cypress Cupressus sempervirens Agriculture and Natural Italian Stone Pine Pinus pinea Resources Jacaranda Jacaranda acutifolia Costello, L. et al Japanese Boxwood Buxus japonica Japanese Honeysuckle Lonicera japonica “Growing Points” Newsletter, Department of Environmental Japanese Pagoda Tree Sophora japonica Horticulture, University of Jojoba * Simmondsia chinensis * California, Davis Fall 2001, Jujube, Chinese Date Ziziphus jujuba Fall/Winter 1996/1997 Lemon Bottlebrush Callistemon citrinus