Sunday, May 3, 2015

Don Shor: Tips for being smart with water

From page A12 | May 08, 2014 |


Adult syrphid fly (hoverfly). The adult feeds on nectar and pollen and is entirely harmless to people. In my garden I find them most often on daisy flowers and single-petalled roses. Don Shor/Courtesy photo

What’s the lowest-water way to water my lawn? I can’t really afford to get rid if it, and I want it to look as good as possible.

For years we’ve recommended giving lawns one inch of water, two times a week. While that is optimal for fine-bladed grass blends at the highest water-use times of year, you may find your lawn can get by with less.

Try watering once a week at first. Run your system long enough to put a little more than one inch of water into a measuring device (tuna cans, cake pans, or any other cylindrical device). Check to make sure the edges and corners are getting sufficient coverage. Most sprinklers will take 30 to 45 minutes to provide that much water; some will take longer.

Then turn off your timer. After a few days, walk around the lawn with a screwdriver and start poking it into the soil. If it slides in easily to a few inches, you’ve still got sufficient soil moisture. If it is hard to push in, the soil is drying out.

For much of the season you may be able to get by with one good soaking a week. Then if we get hotter than average (95 degrees or more) or have one of our north wind episodes, you can run your sprinklers manually for a second time that week.

In the long run, your best bet is to reduce your lawn area and overseed the remaining turf with a lower-water grass species.

How about roses? I’ve heard they like a lot of water.

Roses grow and bloom best if the soil is evenly moist, so most people like to water them twice a week or even more often. But the plants will survive considerable drought. So a happy medium is to do as I just outlined for the lawn: water the rose bushes thoroughly once a week, then again only during periods of high water demand such as hot and windy spells.

Soaking them at the ground level is best; you don’t want to be routinely spraying water onto the leaves. But every week or so, washing off the foliage is actually good for roses: it removes aphids and other pests, and reduces powdery mildew. Most bushes will grow and bloom adequately with once-a-week watering. Again: if it’s very hot or windy, wash off the foliage and set the hose on each bush for another good soaking. And a couple of inches of mulch can help keep roots cool and moist.

A general note about roses. My experience is that the summer appearance of the long-stem cutting roses (hybrid teas) can be rough here. But cluster-blooming types have enough flowers, with new blooms opening each day, that they look good in the landscape even during hot spells and with less water. This includes roses classed as floribundas, grandifloras, and the catch-all categories of landscape and shrub roses. You’ll probably be happier overall with your rose garden if you add some of these, even as you choose to water less frequently.

I’ve heard you say we can water bigger trees less often. All trees? Or are there some I should be concerned about? And should we water more because of the drought?

Regarding the drought and big trees, there was a great letter to the editor in The Enterprise from Kathryn Dixon on April 16:

“For trees in their first year, deep-water two to three times per week for the first two months. Remember to water more frequently during hot weather. After this period, water twice a week to keep the soil moist (not wet) until the winter season.

“Trees in their second year require weekly deep watering beginning in late spring through early fall. Those in their third year or older need monthly deep watering during the dry season.

A good technique for checking soil moisture is to poke an 8-inch screwdriver into the soil. It is time to water if the screwdriver cannot easily pass through at least 6 inches of the soil.”

She also stresses the value of mulch spread around trees to conserve moisture. Just remember that the mulch should not be up against the trunk.

Looking at leaf samples recently, and after numerous conversations with folks who are removing their lawns to plant low-water landscapes, I do need to add a note of caution. Some tree species are much higher water users and could be stressed if they aren’t given additional watering.


* Birches — European white birch is the type commonly planted in this area, usually in attractive groups. Stressed birches are more prone to infestation by borers.

* Coast redwoods — Spring needle drop is natural on these, but is made worse by drought. Stressed trees will have scorched, grey-tipped needles, and may become vulnerable to infection by a fungus disease (Botryosphaeria).

* Magnolias — The deciduous flowering types such as “tulip tree” will show a lot of leaf scorch if they get stressed. The larger glossy-leaved Southern magnolias will have increased leaf drop.

* Maples — In general, maples are not drought-tolerant and will look and grow best if not allowed to become drought stressed. Summer leaf scorch is common on underwatered maples.

The trees I’ve listed should be watered deeply every one to two weeks through the summer. If you are changing your overall watering, and the area around them will now be getting much less water than it used to, they could show severe stress when we get our usual summer heat. But you don’t have to revamp your whole sprinkler system just for a few of your trees. You can install a small drip or micro-irrigation system for the specific trees in question. Or just go out and buy a cheap soaker hose, run it zig-zag under the canopy of the trees, and attach it to a hose. Turn it on every couple of weeks and let it run at a very slow trickle for several hours or overnight.

Bugs bad and good?

* What are these little round things on my plum tree? They’re black and they’re clustered all along some of the branches.

That is lecanium scale. Scale insects are actually related to aphids. Recent samples have been on plums, apricots and pluots. They suck the juices from the plant and drip sugary excrement that often attracts ants or grows a black mold. The hard, waxy coating protects them from pesticide sprays and predation, although there are some beneficial insects that feed on them. Only the youngest stage, called the crawler, moves on the plant.

While some pesticides such as oil sprays help control scale, I have found that mechanical control is by far the simplest and most effective: blast them off with a pressure washer. I don’t mean a little hose nozzle. I mean the kind of pressure washer that you might use to wash your car. A very strong blast of water a few inches from the branch will dislodge most of the scale. Nontoxic, harmless to the plant, fun to do on a hot day; repeat as needed. You can buy pressure washers from Davis Ace Hardware and auto supply stores.

* I found this thing on my rose bud! Is it eating the roses? It looks like it’s just sitting there!

I know it looks like a caterpillar, but the soft green “worm” on your rose bud is actually the larva of the syrphid fly (also called a hoverfly). The larva eats aphids! The adults can often be seen hovering around flowers as they feed on pollen and nectar. Plant more daisies and single-petalled roses to attract them to your garden.

For more information about beneficial insects that are hard at work in your garden, visit the UC Davis IPM website at and do a search for “natural enemies.”

— Don Shor and his family have owned the Redwood Barn Nursery since 1981. He can be reached at [email protected] Archived articles are available on The Enterprise website, and they are always available (all the way back to 1999) on our business website,





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