Chinese Elm (Ulmus parvifolia) is one of the most popular and beloved trees grown as bonsai. Tiny leaves coupled with delicate branches and a robust trunk, along with tolerance of grower mistakes makes it a "can't miss" as a recommended choice for the beginner. Many growers are successful siting their Chinese elm indoors year round in a warm sunny window throughout the spring and summer; but they ensure to provide a much cooler (40F - 55F) location in the fall and winter seasons. We've tried this method and found over the course of a few years the trees have gradually declined and exhibited an obvious loss of vigor. We have also tried the other route and grown our Chinese elms outside like most other deciduous trees (ie maples, hornbeams, etc). We protect them from wind and bright sun in winter, but allowing to get cold (even freeze) like our other hardy trees. (Please note that we are located in Southeastern PA - its not Minnesota cold but still winter cold.) Come spring, the elms just explode with new growth after their winter rest and conservation of energy. When the weather starts to warm up, they just want to grow... and do grow! Obviously YDB will continue to grow Chinese elm outside - but, if you're successful growing your elms indoors, then continue to do so.
These 3 photos were taken in early spring - you can see the new leaves popping out all over.
These next couple of pics were taken of the elm in the center of the 1st photo just last week and you can see that it's really filled out and needs some trimming to get back into shape :-)