Caring for Trees during a Drought

California sycamore (Platanus racemosa)

We have eight sycamore trees on our property, planted about thirty years ago. They have survived on lawn sprinkler water and winter rains and I had hoped that el nino would provide deep watering this year. It appears that drought conditions will continue and it is possible that even more watering restrictions will be imposed.
What are suggestions for keeping these and other mature trees alive during less than normal rainfall periods? how much water is required to sustain various trees?
— Bob Ogg, Granada Hills

Most Important Roots at Drip Line (imaginary circle below tree canopy perimeter)

The most actively growing and therefore important roots of any tree are those found at the drip line — that imaginary circle directly below a tree’s canopy perimeter. It’s called the drip line because it’s where water drips off a tree’s outermost foliage when it rains.

I would give a serious soak to the soil by moving a slowly trickling hose along the drip line of each of your trees. It might take you a few days to complete this process. Alternatively, you could run drip tubing over the drip line of each tree and leave the water on for 24 hours. You would not necessarily have to get drip tubing for all eight trees but, each day, you could move the circle of tubing from one tree to the next.

Deep Soaking

This deep soaking should be done at the end of spring, so that your soil can store up water before everyday hot weather is upon us, and probably again two months later, depending on how hot it gets this summer. If you were to cover the soil between trunk and drip line with four inches of mulch, this would probably eliminate the need for a second irrigation. Note: make sure mulch does not touch your tree trunks. Contact tree trimming companies and tell them to dump their wood chips on your driveway. They will be happy to oblige since this will save them the expense of dump fees. Then wheelbarrow the chips over to your trees.

I am assuming your trees are California sycamores (Platanus racemosa), which are native to the Valley. Although they are riparian trees, which means they grow near rivers, ravines, canyons — note their presence in Topanga Canyon — or wherever water collects near the soil surface, they are nevertheless quite drought tolerant once mature, and grow well without any summer irrigation as long as we get our average 15 inches of rainfall. However, during a long term drought, such as the one we are presently experiencing, applying supplemental water is a good idea. Even native oaks, which will also suffer during prolonged drought, would benefit from a good soaking now and then.

Before Invention of Sprinklers, Orchards Thrived in Southern California

I learned only recently (see last week’s column) that, during the 1880‘s, prior to the invention of sprinklers, orchard trees in our area were watered two to six times during the summer, depending on species and microclimate, by a variety of deep soaking methods. A mature sycamore, although much larger than a fruit tree, would be fine with one or two such waterings during the growing season, especially with mulch in place, following a dry winter. Other trees from dry climates would receive the same amount of water while more water needy trees — such as birch, alder, and ornamental pears and plums — would benefit from deep soaking once a month, provided they were not growing in lawns, which would otherwise soak up much of the water and necessitate additional irrigation.

Before leaving the topic of California sycamores, it is appropriate to address two fungus conditions that are widely seen on sycamores of all types, bringing distress — albeit misplaced — to tree watchers everywhere. The first fungus is powdery mildew and the second is anthracnose. Powdery mildew, prevalent throughout the growing season, is recognized by a fuzzy white layer on leaf surfaces, puckering the foliage. Anthracnose is a fungus that is most active in spring, laying waste to twigs, buds, shoots and leaves, with burnt and crinkled foliage the most visible symptom. These fungus conditions are found wherever sycamores grow, even among the wild ones in Topanga. While these maladies may be treated with chemicals, when ignored they are not life threatening. Sycamores have strong immune systems and often live for several hundred years, despite annual infestations of these fungi.

non-irrigated artichokes, courtesy of Pamela Boothe

My artichokes are out of control! I never planted and they keep reproducing new plants every year. I never water but the fruit is not tasty! Oddly enough I’ve lived here almost 27 years and never planted anything but corn and tomatoes! Never artichokes! And then a few years back – boom! I have huge plants and see new small ones sprouting!
And they are hard to kill!
Any suggestions for better taste and plant control?
Pamela Boothe, Hidden Hills

Your experience speaks to the resiliency of this Mediterranean wonder. Artichokes (Cynarus scolymus), which belong to the daisy family of plants, have highly ornamental silvery foliage and attractive lavender flowers. The part fit for consumption is the unopened flower bud so if you see flowers you missed the harvest.
The previous resident of Boothe’s property must have planted a packet of hybrid artichoke seeds and the seeds those hybrids produced lay dormant for years prior to germination. The reason these artichokes lack flavor is because the offspring of such vegetable hybrids are typically bland when it comes to their edible parts. To be assured of continuously flavorful produce, plant heirloom seeds. The seeds of these vareities from the “old country” grow into plants whose seeds, in turn, will yield produce that matches the quality of their parents. One such heirloom is ‘Green Globe’ and you can procure its seeds through rareseeds.com. You can also propagate artichokes clonally from basal cuttings.

hanging balcony planter, courtesy of Esschert

bridge or rail planter, courtesy of Exaco

Tip of the Week: Jaime Sirgainy sent an email query regarding sources for rectangular planters designed to hang from balcony railings. If you do an amazon.com search for “balcony planters,” you will find them there. Hanging balcony planters by Esschert are especially artistic. You will also notice less expensive bridge or rail planters that are saddled onto the balcony railing itself.

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