As on Feb. 13, the only apparent source of pressure was root pressure, perhaps drawing water as the result of evaporation at the surface of the exposed xylem rays. The reduction in quantity of ice may well have resulted from the lack of rainfall since mid January. Even so, numerous plants are already putting forth green shoots for the coming season. These are apparent in the photo above right, for the two larger plants shown on other pages.
Of some interest is the minimal ice formation with a potted plant, shown below, that had been extracted in order to show its roots on January 26. It did not produce crystallofolia on Feb. 13, but now that its roots seem to have recovered and established new root hairs, the roots provides a source of pressure. The pot sits in c. 2 inches of water, so there is abundant moisture, and this seems to have contributed to the growth of new shoots.
A selection of pictures from Feb. 27 (click to enlarge):
Detail of large plant shown at top of page (right).