Wednesday, April 18, 2012
Yesterday was a weather pleasant day. Clear skies and warm afternoon air made overnight frost seem unlikely. A steady wind from the north was an easily overlooked clue that frost was waiting in the wings. Fortunately our local weather forecaster posted a frost advisory and we put our modified lily sod house with its new tarp cover to the test. Partially water filled plastic juice bottles provided weight to hold the tarp in place. A wake up temperature of 30 F placed a skin of ice inside of the bottles. Icicles grew down from the water surface looking like cave stalactites. Temperature inside the tarp, measured at ground level, was 37 F. Newly emerging lily tips were spared a freeze.
These purchased trout lily, Erythronium, leaves were painted by frost. The more narrow brown mottled leaves of our native trout lilies were unmarked. Positioned nearer the ground they escaped frost markings. Just how the frost swirls around is poorly understood here. In the upper photo the grass at the base of the slope remains green showing no trace of frost. In the calm night air the cold seems to pour downhill striking some areas while skipping over other spots.
Frozen Quaker Ladies, Houstonie bleue, flowers present a striking image. When the sunlight melts the frost these flowers will look bright and fresh unfazed by being frozen.
Becky and I removed the tarp. It did a great job. We carefully folded the 16 by 24 foot tarp and put it away in the shed. We are going to get a lot of practice in tarp handling. Frost warnings have been issued again tonight. I guess by the time we get really terrific at doing this we won't need to do it anymore!