   La Niña Gardening - November 28, 2007 Jeff Schalau, Associate Agent, Agriculture & Natural Resources, Arizona Cooperative Extension, Yavapai County The arid southwest is no stranger to drought, but as populations continue to grow and drought conditions continue to intensify, we must consider adjustments to our gardening and landscape practices. La Niña conditions have developed in the Pacific and forecasters have predicted below average precipitation and above average temperatures which are likely to persist through spring. Below we will discuss what causes a La Niña condition and some horticultural practices that can mitigate the impacts of drought on gardens and landscapes. The term “La Niña” is used to describe an important fluctuation in sea surface temperatures and wind flow in the equatorial Pacific Ocean. In general, it means the sea surface temperatures are cooler than normal in the eastern Pacific Ocean. This means that clouds are less likely to form in the eastern Pacific where they could potentially deliver winter moisture to the southwestern U.S. Cooling in the eastern Pacific also causes the jet stream to be pushed north further decreasing the probability of winter precipitation in the southwestern U.S. Irrigation is the most critical gardening practice to consider during drought. Evergreens are often the hardest hit during winter drought periods because they continue to require water for photosynthesis. Evergreens include conifers such as pines, junipers, and cedars as well as large shrubs like Photinia. Deciduous trees and shrubs require less moisture, but will benefit from some irrigation if we do not receive any precipitation. For trees and shrubs, infrequent deep irrigation is more desirable than frequent shallow irrigation. If water restrictions are implemented in your community, follow them. Mulches are very effective at reducing evaporation at the soil surface. Organic mulches, such as bark or wood chips, are best because they add organic matter to the soil as they decompose. Gravel mulches are effective in winter, but increase heat at the soil surface in the summer which does not help with water conservation. Mulches can also reduce competition from weeds which will make more soil moisture available to garden and landscape plants. You can have color in the winter. Many annuals, perennials and herbs are cool season plants. Pansies, stock and snapdragons are annuals that can be planted in the fall to provide color in early spring. Ornamental kale adds color and is edible. For these annuals, soil should be amended with compost to increase water holding capacity. Native and/or drought-adapted wildflowers usually do fine without major soil amendment. Penstemons and other native perennials do best on well-drained soils without soil amendment. Rake up those leaves and trimmings to start a compost pile. Homemade compost is an excellent soil amendment and reduces waste going into the landfill. Simple composting systems can be built from used pallets or sheet metal. Fencing and chicken wire compost bins loose moisture very quickly in our climate. Compost bins with solid sides conserve moisture which is critical to decomposition of organic matter. If you have large areas of turf, consider replacing them with other less water consumptive ground covers. Native grasses and wildflowers are excellent choices for drought-tolerant ground covers. Creeping thyme is an excellent choice for growing between flagstones on walkways. They also add fragrance to your landscape when walked on. Cacti and succulents can also add interest to your landscape while conserving water. Remember to use them appropriately and where they will not pose a safety hazard. You may also want to consider water harvesting. One water harvesting technique involves collecting precipitation from your roof and storing it in barrels or cisterns for later use. This method requires some planning and an investment in materials. The more simplistic approach is to contour the soil surface to collect overland flow and allow it to infiltrate before it leaves your property. I hope the above ideas are helpful and remember that drought is one of the characteristics of the southwestern US. Do your part to conserve water in your landscape, orchard, and garden. The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at cottonwoodmg@yahoo.com and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/. |