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Crystallofolia on a Cut Stem of Pluchea odorata

by Bob Harms ()

With the first crystallofolia on P. odorata on Dec. 25, 2007, I collected a stem specimen (shown above), cutting well below the ruptured epidermis, leaving a stump 30 mm. above the ground. With the next frost, Dec. 29, I was surprised to find petal-like ice formations around the stump, and that afternoon I noted that the epidermis and cortex had pealed back from the hard secondary xylem. To my further surprise it ‘bloomed’ again on Jan. 1, and yet again on Jan. 13 — reduced with each occurrence, but always with laterally formed bands from the xylem rays. A repeat on Jan. 20 with a freeze of 18° F was slightly larger, possibly by virtue of a recent rain of 0.3 inches or the fact that the newly developing leaves at the base were now larger (and capable of generating more pressure with extracellular freezing). And the ice crystals in the ribbons were also thicker and clearer, in contrast to the earlier forms. During that period the soil had remained moist, and new shoots had emerged at the root/stem interface, indicating robust root activity.

Stem cut just above base, Dec. 29

View from above

Lateral view

Same stem in the afternoon

Cut stem as above, Jan. 1

Cut stem, Jan. 13

From above

Lateral view


Cut stem, Jan. 20. [B = base of stem, C = detached cortex, E = intact epidermis, L = leaves, S = shoot]

From above

Lateral view

Later in the day, debris removed at base;
piece of epidermis/cortex torn off above the shoot (S).