Water woes--the facts about our water

"Water, water every where,

Ne any drop to drink."

said Coleridge’s Mariner (probably the only part of the poem most people remember, except the part about the albatross…)

Well, the water was everywhere and ample, but salty, much like the water in Davis, Woodland, and all the parts of Yolo County north of Putah Creek. Different types of salts have different effects. Water with sodium is "sweet" or "soft"–it tastes better, and soaps and detergents work better. Our water has calcium and other salts, which we call "hard." Sodium is toxic to plants, so you should never water your plants with water from your home water softener. Calcium and other salts are not toxic to plants, but in excess can make some old favorites difficult to grow here.

Ground Water West of the Causeway

Sacramento is the Camellia City, yet Camellias are considered tricky to grow in Davis, just 20 miles away. Why? Because of the clay soil and the hardness, high pH, and boron content of our water. Sacramento has river water–pure melted snow. Davis water comes from underground and contains salts that filter down from rock formations in streams, particularly those that feed into the outflow from Cache Creek. One tributary has rocks that are high in borax, and calcium, manganese, and other minerals steadily leach into our water from other streams. Water in Dixon and Winters causes fewer problems because the water from Putah Creek, which recharges the ground water in those two areas, doesn’t contain as much boron.

Groundwater can have health issues. Shallower well water may contain the byproducts of farm fertilizers, particularly nitrates, and often contains selenium because it is a naturally-occurring mineral in soils on this side of the valley, so regular testing is done for these and other contaminants. Most of the wells draw from aquifers about 300’ deep, but four are deep wells drawing from over 1000’ deep. That is prehistoric water, which is warmer, less hard, and less salty than the shallower wells. These have more boron and about the same pH as the shallower wells. This water is healthier for people, with much lower nitrate and selenium levels, so the city is pursuing pooling of water from the deep wells on the UC Davis campus with the city water supply. There are even long-range plans to bring river water from West Sacramento, which would delight gardeners here, but don’t hold your breath.

Salt-sensitive plants

Hard water makes it difficult to grow "salt-sensitive" plants. The salts burn the leaves and stunt the growth, eventually killing the plant. Flowering dogwood (Cornus florida) and Rhododendrons almost never do well here. One customer saves enough rainwater to water his rhodies all season--build a cistern and you can try them. Another metered muriatic acid into his outdoor water supply--clearly a labor of love. I have never seen a successful Cornus florida in Davis. Other plants will grow fine but will get an unsightly leaf burn on the tips and margins of the leaves. Examples include Evergreen clematis (Clematis armandii), a landscape vine, and Piggy-back plant (Tolmiea menziesii), a house plant.

High pH and plants

Symptoms of high pH (alkalinity) and excess boron are similar and are increased by shallow watering in clay soils. Plants get stunted and the new leaves are yellow. High pH makes iron unavailable to the plant, which leads to yellow leaves with green veins, and can also cause zinc deficiency which is characterized by stunted, small leaves–all on the new growth. Excess boron may also cause burnt leaf margins, and especially causes dead areas on older leaves of broad-leaf evergreens such as holly and Camellias. Boron is very soluble, so deep watering in porous soils will move it out of the root zone. Boron toxicity often occurs on plants under a roof overhang as this prevents leaching of salts by winter rain. Drip irrigation systems cause problems when they are run for short periods–you can see the buildup of white salts on the edge of the watered zone. Deep soakings in amended soils will significantly reduce boron toxicity.

Plants that prefer low pH

The classic "acid-loving" plants include Camellias, azaleas, Gardenias, and Japanese maples. All of these like lots of stuff added to our clay soil when they are first planted. Don’t skimp on the organic soil amendments! Dump a bag of good planting mix on the ground and mix it with your native soil, turning it in to an area at least 3’ across. Porous minerals such as pumice or perlite will improve drainage and hasten the movement of salts and boron out of the root zone. (Sand can be counterproductive: sand particles interlock with clay particles to form a concrete-like soil structure.) Add products containing sulphur to lower the pH, and fertilizers specifically labeled for these plants. The work you do when you plant them will make all the difference! Follow up after planting with regular feedings and applications of pH adjusters.

Camellias and azaleas

are great companions, preferring partial shade and rich, moist soil. Camellias are stars of the winter garden with their elegant flowers, and are among the least fussy acid-lovers. There are many mature specimens in College Park and the downtown area. Keep them evenly moist, and give them an occasional deep soaking to remove the salts from the root zone. Azaleas are dramatic in the spring, but are fussier. If you’ve already amended the soil for Camellias, plant a few azaleas and enjoy them for a few years. Their spectacular bloom in early to mid spring is worth the effort. Azaleas have shallow feeder roots and can’t tolerate drought. There are numerous other plants that love the special attention you're giving these acid-lovers. Mix in some ferns, columbines, coral bells, and Japanese anemones for a colorful understory planting.

Gardenias

are prized for their rich, sweet fragrance. They love warmth, and grow fine here as long as you plant them in rich, porous soil and fertilize them regularly to reduce the pH. Unlike the others they bloom best if they get at least some direct sun and won't bloom well in too much shade.

Japanese maples

(Acer palmatum) are very graceful small trees. Some have vivid burgundy leaves, coral bark, or finely dissected leaves. However, they don't like hard water, heavy soil, high pH, or dry winds--just a few strikes against them on this side of the valley! Plant them where taller trees will protect them from sun and wind or the leaves will burn badly during our famous North winds. Enrich the soil, adjust the pH and fertilize regularly, and keep them evenly moist. Occasional deep soakings will help leach the salts from the root zone. They grow best in older neighborhoods with a mature canopy of larger trees. In new neighborhoods consider Acer truncatum, the Chinese maple, as a less fussy substitute.

The following plants prefer acidic soil conditions, so amend the soil and fertilize regularly as described above:

For more information...

Water quality analyses are available from the city Public Works Department, and my thanks to Bob Schoech –pronounced Shay–for his help. For more information about City of Davis water projects, visit their web site at City of Davis Public Works Dept

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