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Keep plants healthy through winter by regularly checking their moisture levels

Yellow leaves litter the ground below the ginkgo trees at Courthouse Park in downtown Fresno after a morning rain storm blew through the Valley.
Yellow leaves litter the ground below the ginkgo trees at Courthouse Park in downtown Fresno after a morning rain storm blew through the Valley. ckohlruss@fresnobee.com

The majority of our rainfall (annual average 11.6 inches) arrives in the early spring. Rainfall in December may not be enough to thoroughly soak the soil. Check soil moisture levels weekly, even after rain, to see where supplemental irrigation might be needed. Our winter rain storms generally come from the northwest or west. The soil on the east and south sides of buildings, fences and large trees or eaves and patios that block the rain be much drier than on the northwest sides. Increase irrigation times in the drier areas or hand water. Remember to turn off all irrigation during rainstorms.

Elinor Teague

Large tree canopies also block rain from soaking the roots under the canopy. If rainfall is light this winter, large landscape trees will need slow deep irrigation monthly until the rains come in spring. Place soaker hoses, bubblers or multiple drip emitters around the edge of the canopy where the “feeder” roots lie about 1 foot deep and allow the water to slowly soak the soil over a period of three to four hours to a depth of at least one foot.

Container plants often don’t get enough water from rainfall in winter. Stick your finger into the soil every week to check moisture levels and irrigate until water comes out the drain hole when the top inch or two of soil is dry.

Check your compost pile for moisture content. A soggy pile will rot and smell like ammonia; a dry pile will not decompose. Add water to keep the pile slightly damp as you turn the compost and cover the pile with tarps when it rains.

Soil pH levels in cooler, wetter climates than ours (like the Pacific coast) are much lower than in our arid, hot climate. Soil pH levels there are neutral or acidic, below 6.5-7 pH. Our soil and water is highly alkaline, above 7 pH, with high amounts of salts that are not flushed out of the soil or diluted by our low amounts of rainwater. Most plants grow best in soil with a neutral or slightly acidic pH. We often see chlorotic, yellow leaves on shade-loving plants like gardenias and azaleas, which indicates that the high pH soil and water levels are interfering with the plants’ ability to draw up iron. Last year’s wet winter with well above average rainfall will have flushed some of the salts buildup, but not all of it. Allow hose water to run for a half hour underneath chlorotic plants to help flush the salts. Do this monthly during December and January and into the spring months if rainfall amounts are below normal.

Free class on tree care

The University of California Cooperative Extension Master Gardeners of Fresno County are offering a free class on fall and winter orchard care on Saturday, 9:30 to 11:30 a.m., at the Garden of the Sun, 1944 N. Winery, Fresno. You don’t need to have an orchard, just one backyard peach tree will do. Learn proper fruit and nut tree care and pruning from an expert and bring your loppers; you’ll be practicing what you learn. Contact the UCCE office at 559-241-7519 for registration information.

Send Elinor Teague plant questions at etgrow@comcast.net.