Unbelievably, it is time to start thinking about autumn, at least in terms of caring for our plants. The average first frost date is Sept. 15, but in colder areas or microclimates, freezing temperatures are likely to occur sooner.
Just as we winterize irrigation systems, plants have to winterize themselves in order to reduce or avoid adverse physiological reactions to freezing temperatures. This means that growth has to slow before a freeze hits. In many parts of the country, the temperatures drop gradually, allowing plants a long period to shut down. In Nevada, we are much more likely to have 80 to 90 degrees one day, and a sudden drop to below freezing a couple of days later, when we least expect it. These sudden freezes can seriously damage plants that are in full-growth mode. Damaged growth encourages diseases, and diseased plants often have a hard time surviving our long, dry winters.
Plants that are slightly stressed for water actually suffer less dieback or disease development in response to low temperatures. Reducing the frequency or intensity of watering starts the plant shutdown process. However, knowing exactly when to reduce water to slow plant growth is tricky when the daytime temperatures are still in the 90s.
One way to reduce water for well-established plants is to water deeply and less often, allowing the soil to dry out between irrigations. Another method, for more shallow-rooted plants, is to reduce the amount of water applied with each irrigation. Both practices send the signal that water is less available, which slows plant growth.
Another important factor to consider as we ready plants for the upcoming freezes is to avoid fertilizer, other than slow-release, organic or low-analysis types, until after a hard freeze. Fertilizers, particularly those high in nitrogen, stimulate growth. At this time of year, freezing temperatures damage or kill new growth, except on the hardiest of plants or those in warm microclimates. This is especially true for roses.
While you are thinking about plants, head down to the great farmers market at Curry and Telegraph in Carson City, 9 a.m. - 1 p.m., this Saturday, Sept. 6. Tammy Westergard will talk about community gardens, and Mary McDonald will tell you everything you need to know about fall bulbs. The presentations will occur every hour, 10 a.m. to noon.
For more information on gardening, contact me, 775-887-2252 or skellyj@unce.unr.edu, or your local University of Nevada Cooperative Extension office. Check out many useful horticulture publications at www.unce.unr.edu. "Ask a Master Gardener" at mastergardeners@unce.unr.edu.
n JoAnne Skelly is the Carson City/Storey County Extension educator for University of Nevada Cooperative Extension.
