Tree species have developed different strategies for when they resume growth in the spring. Douglas-fir trees, for example combine shoot growth and extension of new needles so these processes happen simultaneously (the “burst” option). This has the advantage of expanding the tree’s leaf area for photosynthesis quickly. Western white pine demonstrates the “candle” option where shoot growth begins first and expansion of new needles happens later. This option has the advantage of beginning height growth early but not exposing new needles to frost damage and may also potentially reduce browsing pressure. The dramatic twisting and movement in the new shoot of Douglas-fir in a greenhouse demonstrates how changes in the balance between water uptake and water loss via transpiration can result in surprising movements. These movements will gradually decline as plant tissues become more rigid.
