|Tillandsia usneoides grown outdoors in Connecticut and brought inside on December 24 (left) and January 12 (right).|
Tillandsia usneoides grows naturally in locations that experience considerable frost, and would appear to be the most cold hardy of the epiphytic angiosperms (flowering plants). I have grown Spanish Moss outdoors in the branches of trees in Mansfield, Connecticut many times and it always does quite well from spring to fall. Plants that are left out over the winter have never survived, though, even in mild years.
This winter I had left out a number of clumps of extra T. usneoides, but after they had been thoroughly frosted I decided to bring some in to the UConn greenhouse to see if they could be revived. Plants retrieved on December 24 looked a little dehydrated at first but recovered quickly in the greenhouse, with negligible die back. November-December was warmer than normal, but the plants had experienced numerous hard freezes, some multiple-day stretches of sub-freezing temperatures, and absolute lows of about 10°F (-12°C).
Another clump brought inside on January 12 experienced much harsher weather, including week long periods with daytime highs below freezing and absolute lows of -2°F (-19°C). Although this plant probably lost well over 90% of its shoots, a smattering of stem tips with a couple of leaves and internodes have definitely survived and are resuming growth in a cool but frost-free greenhouse. Still, the plant was clearly near the limits of survivable conditions.
|Three different collections of Tillandsia usneoides: typical USA form, gathered in Charleston, SC by R.W.A. Opel (left); fine Carribean form from the Dominican Republic (center); robust form from Peru (right).|
Addendum: I rescued some more clumps of T. usneoides from outdoors in mid-February, after more extended periods of sub-freezing weather. Some shoots still looked pretty green initially, but this was the green of a package of frozen spinach; everything was clearly brown and dead a few days after thawing out.