By Steven Foster |
What are those ribbons of ice traveling up the stem of roadside plants that you may have noticed on a recent early morning? They are “frost flowers”, “ice flowers”, or “ice ribbons” and are found on two plant species at this time of year native to the Ozarks. Those seen on plants in ditches or at the edge of a road are probably from White Crownbeard, Frostweed or Tickweed (Verbesina virginica). A late blooming member of the aster family, it sports ragged white flowers in flat-topped clusters. It’s a plant you probably won’t notice until now—the moment of the first few hard freezes of autumn. The frost flowers form during the first few hard frosts as capillary action draws moisture up the vascular bundle of moist living tissue fed from the roots, then the watery sap freezes, expands at right angles and transforms along the stem into extruded crystals ribbons of beautiful, layered, ice formations.
Another plant found in woodlands, American Ditty (Cunila origanoides), which grows in dry, wooded habitats mostly on west or south-facing slopes, also produces frost flowers. You probably have to go a little out of your way to see them, unless you drive along a forested dirt road early in the morning. This little oregano-scented mint family member is common in our woods. On the first frosty morning of autumn, the still active roots send cell sap toward the stems, now cracked and beginning to die back to the ground. As the sap from the root tries to make its way up the cracked stems, the freezing air turns the moisture-laden sap at the base of the stems into fluted, twisted, layered ribbons of ice that look like Christmas ribbon candy. This phenomena usually occurs only during the first few frosts of the year, though American Dittany can produce frost flowers for several weeks, depending upon soil moisture and weather conditions. Of course, another plant that is a definitive barometer of the season’s first hard freeze is the tomato. If one morning your tomato plants suddenly turn black then likely we’ve just had our first frost.