Using Non-potable Water on Native Plants

Yesterday I attended an all-day conservation forum given by the County of Los Angeles Department of Parks and Recreation called Recycled Water/Plant/Soil Compatibility. There were two talks on the effects of recycled water on soil and plants, and these were pretty technical. Not surprisingly, Debbie Evans from Tree of Life Nursery reported that recycled water is probably not appropriate for use in a commercial nursery. Carol Bornstein gave the talk that I think many people were eager to hear: Native and Drought Tolerant Plants Suitable for Use with Recycled Water.

In preparation for her talk, Carol visited a number of parks in the Santa Barbara area that used recycled water on drought-tolerant plants. She then compiled a list and showed pictures. She was clear that the resulting list is not: the best list, the only list, or even an appropriate list of plants that would work well with recycled water. She pointed out that the idea behind using native and drought-tolerant plants is to reduce the irrigation needed for their success. A better strategy, therefore, might be to use potable water during the occasional years when there is little winter rain. One might even accept the losses that occur during dry years so that over time only plants that can survive and look good in our climate will be part of the parks.

Carol was clear that the plants on her list was based on a small number of parks in the Santa Barbara area, and many of these plants would not be successful in hotter, drier inland areas. She also pointed out that there is no good research comparing how plants perform when watered with potable versus recycled or greywater. Controlled experiments on this would provide very useful and interesting information.

The list was comprised of the fairly typical native plants that one finds in gardens and parks. It was interesting to see how Carol determined which plants she thought would be good candidates for poor water. They were usually coastal plants that receive salt spray or are found in salt marshes, and therefore are tolerant of higher salt levels.

I’d like to pursue this further and want to ask if there are any native plant gardeners who have tried this: growing native plants using greywater water. (I don’t think anyone has access to recycled water for residential landscaping yet.)

Even without field data, ancedotal or otherwise, on native plants and recycled or grey water, it would be helpful to have a list of plants that are more likely to be tolerant of poor water.
Criteria, as suggested above, could include plants found in: coastal areas with salt spray, salt marshes, and heavy soil with poor drainage, especially desert washes where salts and minerals from the soil cannot leach out. I’d also include plants that seem to be tolerate of a very wide range of soils.

Finally, before giving my first stab at this list, Jane Tsong emailed me with information on greywater use in her garden:

For the record, last summer, like a boor, I watered newly planted Encelia californica, mahonias, mimulus, heuchera, eriogonum giganteum, penstemon and salvia apiana among other things with greywater that had traces of soap/shampoo in it. Although all survived but the penstemon, the salvia has never taken off, and I this summer when I used clean water from the hose, all the plants seemed a LOT happier.

As for the list, so far I have come up with the following (please excuse the use of botanical names only, once there is a more complete list I’ll add common names):

Achillea millefolium
Argemone corymbosa
Aster chilensis
Atriplex species
Baccharis pilularis
Baccharis salisifolia
Biden laevis
Carex praegracilis
Ceanothus maritimus (and others found at the coast)
Chilopsis linearis
xChitalpa tashkentensis
Ericameria species
Erigeron chilensis and cultivars
Eriogonum arborescens
E. cinereum
E. latifolium
E. parvifolium
Eriophyllum nevinii
Fragaria chiloensis
Grindelia species
Grasses
Juncus species
Juniperus california
Justicia californica
Myrica californica
Prunus ilicifolia ssp. lyonii
Rhus integrifolia
Shepherdia argentea
Stanleya pinnata
Washingtonia filifera

Any other thoughts?