Having more than five thermometers spaced around the garden doesn’t make you obsessive with the weather, does it? Whereas most folks have one thermometer mounted casually on their back porch, I admit to having a variety of devices displayed throughout the garden. Central Alabama’s rolling mountains and numerous valleys provide a wide range of temperature readings on these cold, still windless nights. Dense cold air, like water, flows downhill to the lowest spot; gardeners who live in frost pockets are usually situated where cold air tends to pool.
My property has a 100-foot drop in elevation that can cause occasional extreme variations in the temperature in a relatively short distance. On clear windless evenings as the sun sets behind the tree-lined ridge, the temperature is sometimes 10 degrees cooler at the bottom of the steep, north-facing hill. By morning, the colder air seems to overtake the entire area and differences are less pronounced.
Deep narrow valleys also offer the prime conditions for creating an aggravating frost pocket. If you are one of those people who is constantly decorating your newly planted spring annuals or vegetables with an array of protective sheets and blankets, having several thermometers even in a modest size garden is not a bad idea. Warm or cold spots in the landscape can be utilized to the homeowner’s advantage. Tomato season can even be extended where warmth exists and plants like Peonies and Hosta benefit from any additional chilling in our mild winter.
I plant cold-loving plants at the bottom of the hill where any additional cold is appreciated. A north wall or afternoon shade would have a similar effect. Frost sensitive plants like bananas, elephant ears, and garden peppers would survive a near-frost experience by relishing the additional warmth provided by a south wall or a sheltering tree canopy. My hilltop garden is often reserved for more tropical plantings since frost can arrive much later than to the valley floor below.
Autumn frosts are a good indicator of frost pockets. Kudzu is often considered a good-for-nothing plant in the Deep South, but makes an excellent frost indicator. Kudzu is highly sensitive to the mildest frosts and blackens like cooked spinach with the first onset of nippy weather. Yet in the depths of winter, especially if you’re not looking to start a garden of Kudzu, an easy solution to determine warm or cold microclimates is by noting and comparing observed temperatures with a handy thermometer.
In the Anniston area, official weather records are recorded at the Anniston airport. The broad open valley situated there along Choccolocco Creek isn’t the warmest location in our area due to the more open, rural landscape. That openness also discourages deep pooling of cold air, thus the airport isn’t one of the area’s colder locations either. In other words, don’t expect home thermometers to always agree with the official report. Elevation and topography are major influences that can cause shifts in temperature. However, the home thermometer can also dictate some of these wide variations.
Home thermometers should always be situated in the shade (but not too shady) and out of direct sunlight. Readings should be taken at least four or five feet above the ground. The least accurate thermometers are spring coil types that are somewhat clock-like with a pivoting arm.
The most common thermometers are filled with alcohol (that red stuff) and are a little less accurate than true mercury types (the silver stuff). Digital thermometer accuracy is very dependent on proper setting. Official thermometers are actually housed in a vented shelter box painted white to provide shade and shelter. Placing a thermometer or sensor on or near a cold metal surface can really skew your temperature.
In conclusion, a few good thermometers properly situated are well worth the trouble; they can really help the home gardener address and understand the numerous challenges of gardening in the South. And having them handy might keep you from fretting if your morning lows don’t always agree with the Weather Channel or local weather report.
