Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
In mid-Michigan many pines are now in the “candle” phase of shoot growth. In pines, shoots grow rapidly in the spring and complete a large portion of shoot extension before needle expansion begins. Candling is significant because pines need to be pruned during active shoot growth. Unlike many other conifers, pines do not form lateral buds along the stem, but instead form a whorl of buds at the terminal end of each shoot. If the terminal buds on a shoot are lost, due to pruning, browsing or pest damage, the shoot will not be able to produce a normal whorl of branches the next year. If we prune a pine shoot during the candle stage we can control the height growth while trees growth pattern will still allow enough time to form the terminal buds for next year. One rule of thumb is that pines should be pruned when the current year’s needles are half the length of the previous year’s needles. Candles may be pruned with hand pruners or a shearing knife. For small pines in the landscape, new shoot growth can be controlled simply by pinching off at the desired height.
It is important to point out that the pruning cycle for pines is in contrast to single-needled conifers such as spruces, firs and Douglas-fir. Single-needled conifers may be pruned anytime they are not actively growing. In single-needled conifers, pruning the terminal stimulates additional bud development along the stem, increasing crown density. Some Christmas tree growers prune firs and spruces in the summer after budset, while others prune in early spring before grow