The Day of the Triffids(1963, 95m, Allied Artists), starring Howard Keel, and Janette Scott. Meteors turn plants into giant walking Man-eaters (which, by the way, is the same basic plot as Little Shop of Horrors, which was, nevertheless, a very different movie). Remade for British TV in the early 80's. There is, by the way, no such thing as a"Triffid," which is the name these plants went by. However, "trifid" (with one F) means "divided into three parts", and is often used as part of the scientific name of plants which have a three-part leaf.