The following was received via email: We had a great Tibouchina in Steveston, BC until the cold temps last week. It was not in the frost but I think the cold has killed it. We have moved it inside but it is not looking good. Will it recover in spring or is it toast? It has dried up and not looking good Beautiful plant and need help.
I have seen them recover from very poor condition. Like the bouganvillea it is hit hard by frost and will usually defoliate rapidly thereafter. I have found that if you keep it at dormant temps for the winter (above freezing but not much above) with some moisture. Cut back to healthy looking wood in early spring and place outside in the sunniest spot (or greenhouse) when danger of hard frost is over. Top dress with steer manure and you will likely be surprised by the recovery.
As a former habitue of Hawaii, I'd characterise both Tibouchina and Bouganvillea as weeds in terms of vitality - at least I had to keep chopping them back so they wouldn't take over the place. Both will return from the worst looking near-death states to delight you again. Which reminds me, I have been meaning to chop my gangly Tibouchina down to about a foot high, but it is still blooming at the tips and I hate to lose any blooms......
First gently scratch the bark. If it is green underneath there is still hope for your plant. If it is black or mushy not a good sign. Give it as much light as you can, do not overwater it & keep the temperature around 55 degrees if you can. If it is long & leggy, prune back. Time will tell how much damage there has been. Don't be discouraged if it drops most of it's leaves.