Teague on Gardening: Has rainfall been sufficient?

Our brief winter season has ended. Plants and trees are coming out of winter dormancy and it’s time to resume a regular fertilization schedule.

During these past four drought years, normal fertilization amounts should have been reduced by at least half. Plants and trees responded to drought stress by slowing growth; feeding them at the normally recommended rates would have forced new growth that could not be sustained given the severe shortages of water. Branch die-back is often more prevalent on plants and trees that were fertilized at normal rates during the drought.

This winter, so far we’ve received above-average rainfall amounts. So do we risk resuming feeding our plants and trees at the recommended rates? Should we count on continued rainfall into spring that will deeply soak thirsty root systems? Before making the decision, we need to check soil moisture levels in our gardens. Your garden will have spots that have received more or less rain than other gardens in the neighborhood, depending on wind patterns and shelter from buildings, fences and overhanging trees.

Take a trowel and, if possible, a metal rod with you to dig and poke into the soil underneath tree canopies, around your rose bushes and camellias, and near the trunk of your sago palms. Try digging with the trowel first, then use the rod to penetrate as deeply as possible. The rod will not penetrate through dry soil. Moist soil to a depth of at least one foot is capable of providing sufficient water for most plants as they begin their spring growth. The soil under mature landscape trees should be moist for 12 to 18 inches at the drip line or outer edge of the leaf canopy.

Some of your trees and plants may need more and deeper irrigation. Use a soaker hose or a bubbler attachment to slowly irrigate drier soil to the proper depth over a period of several hours. Deep irrigation as trees and plants come out of winter dormancy is more important than fertilization. It is critical to sustaining the plant’s health and vigor.

Trees, bushes and plants that are already surrounded by sufficiently moist soil can be fertilized at nearly the recommended rates. Those that still have dry roots should receive half or even less than the recommended rates, even after supplemental irrigation.

High nitrogen fertilizers, especially liquid fertilizers with more than 10 percent nitrogen force rapid new green growth. Applying a lower nitrogen fertilizer with about 5 per cent nitrogen will be less stressful to plants. Organic and granular fertilizers remain available to plants’ roots longer than liquid foods and will be less likely to leach out of the soil if the strong rain pattern reappears in the next few weeks.

Note: The Fresno County Master Gardeners are hosting the semiannual Smart Gardening Conference from 7:30 a.m. to 5 p.m. on Saturday, Feb. 27, at the Picadilly Inn Airport. This year’s timely subject is “The Three D’s of Gardening (Drought, Drip, Design) in a Changing Climate” The cost for a full day of gardening information with more than 20 speakers is $45 before Feb. 24 or $55 at the door. I’ll be talking on “Saving Our Urban Forest” at 11 a.m. The Master Gardener’s website, www.ucanr.edu/sites/mgfresno, provides the full schedule as well as registration forms.

This story was originally published February 15, 2016 at 1:09 PM with the headline "Teague on Gardening: Has rainfall been sufficient?."