Source: Organic Gardener
By Perrie Layton
The larva of a species of tiger moth (Pyrrharctia isabella), the woolly bear caterpillar is also known as a woolly worm. They average about 1 1⁄2 inches long, and are bristly, with black stripes at each end and a reddish brown stripe in the middle. They curl into a ball when touched
Popular folklore claims that the length of the center stripe on a woolly bear predicts the upcoming winter weather. If the black stripes on each end are longer than the middle stripe, the winter will be harsh. A wide center stripe means the winter will be mild. The accuracy rate of the caterpillars, however, has been difficult for scientists to determine. Among a group of woolly bears, the stripes can vary greatly, making their forecast difficult to confirm. Perhaps, like TV weathermen, some caterpillars are correct and some are not.
They eat mostly weeds, including dandelion, clover, and grasses, and generally will not harm your ornamentals or vegetables.
In fall, woolly bears cross roads or paths searching for protected places to overwinter. In spring, they resume eating until pupating in a cocoon made from silk and their own hair. Adult moths emerge in two weeks.Woolly bears are the Dale Earnhardts of the caterpillar world, crawling at a neck-snapping .05 miles an hour, or about a mile a day.
The woolly bear is celebrated with a festival each October in Vermilion, Ohio. Folks in Banner Elk, North Carolina, celebrate the upcoming ski season with an annual Woolly Worm Festival and Race.
Thursday, October 6, 2011
Predicting Frost
Source: Organic Gardener
By Eliot Tozer
As a former Navy pilot who studied how to predict the weather and an experienced gardener, I've learned that a few easily observed atmospheric conditions and the lay of your land will tell you exactly when the first frost will hit your garden. With this information you can plan to protect some plants and get others ready for the compost pile.
Clouds
If the sky is clear, the air is dry, and the temperature is falling, chances are frost will settle on your garden. But if the sky is cloudy, frost is less likely, because low, thick clouds act like a blanket. They prevent the heat that Earth radiates at night from escaping into the atmosphere, keeping frost from settling on your plants.
Breezes
During the day, Earth absorbs heat from the sun. At night, it radiates that heat back into the atmosphere, and cold air gradually settles around your plants. But a slight breeze mixes the somewhat warmer air from above with the cold air near the soil. So frost is less likely on a night with a gentle breeze (but not strong wind) blowing.
Frost Pocket
Cold air is dense. The molecules are packed tightly together, and the air is heavy. It is so heavy that it flows downhill and, like water, pools in low places. The temperature in a valley may be as much as 18° lower than the temperature on the adjoining slope. Likewise, the temperature in your garden varies from a point on a sunny slope near a wall to the hollow in the bottom of your garden. However, trees on a slope will warm the draining air as it passes through because trees transpire, or give off moisture, reducing the likelihood of frost even in the hollow.
Southern Slope
A gentle slope facing south receives solar radiation—heat and light—longer than other sites. And the radiation is more intense. That's why a southern slope is the best location for a garden. Also, cold air drains down slopes (as described in a "Frost Pocket"), so gardens on top of slopes will get frost later than those at the bottom or on level spots.
Trees
Trees act like a blanket that prevents ground heat from escaping into the atmosphere. They also exude moisture, raising the dew point. A vegetable garden surrounded on three sides by mature oaks will survive the first two or three frosts untouched—at least my vegetable garden does.
Walls
Cold air rushing down a slope collects not only in hollows (see "Frost Pocket") but also behind stone walls, fences, and rows of dense vegetation, such as hedges. Frost occurs sooner at the base of these barriers. To delay frost on plants growing beside a barrier, provide an opening in the wall or hedge through which the cold air can drain. On the other hand, a south-facing stone wall is a "heat sink." During the day the sun warms the stones, which release the heat at night, making the plants on the south side of the wall less prone to frost.
Dew Point
As the evening temperature falls, the air holds less and less moisture, until it condenses and dew forms. The temperature at which this happens is called the dew point. When dew forms, heat is released. That heat helps to keep the air temperature at or slightly below the dew point. So, the more moisture in the air at sunset, the less the likelihood that frost will occur during the night. (This is why commercial growers turn on sprinklers when frost is predicted. The added moisture in the air raises the dew point.)
By Eliot Tozer
As a former Navy pilot who studied how to predict the weather and an experienced gardener, I've learned that a few easily observed atmospheric conditions and the lay of your land will tell you exactly when the first frost will hit your garden. With this information you can plan to protect some plants and get others ready for the compost pile.
Clouds
If the sky is clear, the air is dry, and the temperature is falling, chances are frost will settle on your garden. But if the sky is cloudy, frost is less likely, because low, thick clouds act like a blanket. They prevent the heat that Earth radiates at night from escaping into the atmosphere, keeping frost from settling on your plants.
Breezes
During the day, Earth absorbs heat from the sun. At night, it radiates that heat back into the atmosphere, and cold air gradually settles around your plants. But a slight breeze mixes the somewhat warmer air from above with the cold air near the soil. So frost is less likely on a night with a gentle breeze (but not strong wind) blowing.
Frost Pocket
Cold air is dense. The molecules are packed tightly together, and the air is heavy. It is so heavy that it flows downhill and, like water, pools in low places. The temperature in a valley may be as much as 18° lower than the temperature on the adjoining slope. Likewise, the temperature in your garden varies from a point on a sunny slope near a wall to the hollow in the bottom of your garden. However, trees on a slope will warm the draining air as it passes through because trees transpire, or give off moisture, reducing the likelihood of frost even in the hollow.
Southern Slope
A gentle slope facing south receives solar radiation—heat and light—longer than other sites. And the radiation is more intense. That's why a southern slope is the best location for a garden. Also, cold air drains down slopes (as described in a "Frost Pocket"), so gardens on top of slopes will get frost later than those at the bottom or on level spots.
Trees
Trees act like a blanket that prevents ground heat from escaping into the atmosphere. They also exude moisture, raising the dew point. A vegetable garden surrounded on three sides by mature oaks will survive the first two or three frosts untouched—at least my vegetable garden does.
Walls
Cold air rushing down a slope collects not only in hollows (see "Frost Pocket") but also behind stone walls, fences, and rows of dense vegetation, such as hedges. Frost occurs sooner at the base of these barriers. To delay frost on plants growing beside a barrier, provide an opening in the wall or hedge through which the cold air can drain. On the other hand, a south-facing stone wall is a "heat sink." During the day the sun warms the stones, which release the heat at night, making the plants on the south side of the wall less prone to frost.
Dew Point
As the evening temperature falls, the air holds less and less moisture, until it condenses and dew forms. The temperature at which this happens is called the dew point. When dew forms, heat is released. That heat helps to keep the air temperature at or slightly below the dew point. So, the more moisture in the air at sunset, the less the likelihood that frost will occur during the night. (This is why commercial growers turn on sprinklers when frost is predicted. The added moisture in the air raises the dew point.)
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