The start of February marks the midpoint of winter. “Half your hay by Groundhog’s Day,” folklore tells us. While the farmer may measure winter’s duration in terms of preparedness for feeding livestock in the days ahead, the gardener may view the second half of winter as the easier half to endure. The days gradually are getting longer – the sun is rising a greater degree to the east, lifting higher throughout the day and gloriously sinking down into the horizon a bit later than the day before.

But gray! The world is still so drearily gray. Only a fresh snowfall adds brilliance to the colorlessness of winter. To see the green of summer, to feast one’s eyes on the delicate shades and hues, the subtle variations of green between the hollyhock and delphinium, the birch and maple. In the depths of winter, it’s hard to imagine a plant could be anything but a lush, sensuous green.

When we dream about summer’s gardens, our imagination refuses to accept the reality that garden plants are sometimes less than perfect during the growing months. While the winter is harsh on plant material in innumerable ways, dormancy buffers plants from the many environmental difficulties. In summer, plants must keep up with or suffer at the demands of an environment that may quickly weed out the weak from the strong.

The appearance of plant tissue can be an important indicator of plant problems. It is possible to “read” plants for signs of stress. Signs of stress can be found on house or garden plants that are mismanaged or subjected to adverse environmental conditions. Keeping plants in balanced health can be tricky. From the most succulent blades of grass to the mightiest oaks, careful attention to a plant’s inherent needs and its response to the natural environment in which it exists is essential in preventing disease.

Many plant problems arise when plants are subjected to extremes in soil moisture. Too much water can be as detrimental as too little irrigation. While environmental humidity is critical for some, all plants are subjected to fluctuations in soil moisture. Moisture in the soil is lost through evaporation – the movement of water up through the soil profile, across the soil surface and into the air. Moisture also is lost through transpiration – through tiny holes called stomata in the undersides of leaves.

Collectively, moisture loss through the soil and plant tissue is called evapotranspiration. Drought occurs when the rate of evapotranspiration exceeds the rate at which a plant is able to acquire water.

In cultivated plants, drought can occur when we fail to supplement rainfall with irrigation. A state of drought in plants is dangerous because it opens the door to plant disease. Perhaps we should view preventing drought as a vital means of preventing disease in plants.

Plant leaves indicate disease with symptoms that allow us to make a diagnosis and take action for controlling further plant damage. From sun-scald, cold injury or frost damage to nutrient deficiency and environmental mismanagement, plants warn the gardener with symptoms that provide a clear indication that changes in culture and cultivation are required to keep our houseplants and garden plants in a healthy balance.

Sun-scald damage in plants can be noted on leaves or fruits. On geraniums, sun-scald can take the form of bright red leaves. On pepper plants, scalded fruits develop purple striations. In some plants, sun-scald takes form in irregular-shaped browned lesions on the leaf surface. Sun-scald occurs when leaves or fruits are not properly protected from intense rays of light. Sun-scald can be minimized by maintaining an adequate water supply in environments that provide less than ideal light conditions for plants.

Nutrient deficiency in plants can be difficult to diagnose. Symptoms differ by nutrient and by plant species and cultivar. Subtle differences in symptoms can be reflected in the symptoms on plant tissues. Yellowing, bronzing or purpling of leaves may occur. Plants may be stunted or develop a poor growth pattern as a result of nutrient deficiencies.

Frost damage can also be reflected in plant tissue. Leaves affected by frost often develop silver patches on their surface. The upper leaf surface often separates from underlying tissue. While there is really no practical cure for frost damage other than eliminating the affected leaves before they give rise to secondary fungal disease, it is possible to prevent it to some extent by using row covers on garden crops.

For more information about diagnosing plant diseases, visit the University of Maine Cooperative Extension Web site at ww.umext.maine.edu or contact the local Extension office for a catalog listing publications that are informative about particular plant diseases.

Diana George Chapin is the NEWS garden columnist. Send horticulture questions to Gardening Questions, RR1, Box 2120, Montville 04941, or e-mail them to dianagc@prexar.com. Selected questions will be answered in future columns. Include name, address and telephone number.