Hi Gang, Many Eucalyptus species, and some related plants, make a lignotuber. I'm not sure what a lignotuber is anatomically, but I think it is some sort of stem-perhaps like a potato storage organ. Lignoubers allow Eucalyptus species (and Corymbia species, which used to be classified as Eucalyptus) to regrow after fire or other damage. The lignotuber is a tough storage organ, and because it is underground can allow some species to survive 1 or 2 zones of colder temperatures than they might prefer. I've had good luck with Eucalyptus citriodora (Corymbia citriodora), the lemon scented plant. In the wild the tree can reach 60-100 ft-tall. In my garden growth is more modest. However, the benefit of a lignotuber is that (at least some) eucalypts can behave as dieback perennials in areas that are much too cold to allow tall tree growth. Many mallees, some trees, and some odds-and-ends species will perform well in climates that are too cold to allow a "real" tree or shrub to develop. The plants freeze back each winter and sprout stems that can reach 6-8 feet-tall each growing season. The benefit is especially nice with plants that make beautiful foliage or which have strong and acceptable scents. I do enjoy E. citriodora, a sprig can perfume a room with a pleasant lemony scent. One other Eucalyptus that I grow is E. viridis. This plant does well here and, so far, has not suffered from root diseases that plague other eucalypts I have tried to grow. E. viridis is a modest appearing plant, but has wonderfully fragrant leaves that provide oils that are used in soaps and cough drops, etc. The main thing is that, for me, I treat these plants as bulbous-growing things. If/when temperatures threaten to go very low, I mulch the plants heavily, and let to tops freeze. In the spring, with warmth and some water (warmth is key), the plants return and make a garden into a better place, pleasing the nose as well as the eye. NOTE: I've tried various eucalypts here in the greater Houston, TX area. Many survive the climate and thrive for 2-3 years only to succumb to root diseases. I've had some luck growing the plants from seeds in sterile soils (microwave baked) and letting them get large before planting out-then I give them the best drainage I possibly can. TWO WINNERS (SO FAR): 1. Eucalyptus citriodora 2. E. viridis I hope to try more mallee types in the future (shrubby or with many stems from the base, not trees but 10-30 ft-tall). LINK: Australia Plants, source of many seeds and some seedlings http://www.australiaplants.com/ NOTE: Eucalypts can grow 4-8 feet in a year, even from seed. LINK: The Hardy Euclalyptus Page http://www.angelfire.com/bc/eucalyptus/ LINK: Eucalyptus camaldulensis, a lignotuber seems optional in this species http://www.publish.csiro.au/paper/BT9830283.htm