Healthy pines, growing in a sunny location, have a shape which is characteristic of the genus. Their crowns are sparse, which is natural. Pines do not become any denser when pruned, since they have no dormant buds; they also do not respond to rejuvenating in the way that deciduous trees would. Only dry or damaged branches can be pruned out.
Recently gardeners have become interested in techniques of how to train pines. The plants do not always look the way one would like them to. It is too often, that we hear that pines are “too small”, “too tall”, “too thin”, “irregular”, “grow too slow”, “grow too fast”…
One of the most popular questions is how to make a dense hedge of the mountain pine (Pinus mugo). Most nurseries sell adult pines, which are too mature to be planted in a hedge. Even a deciduous hedge is not easily brought back into shape, if left to grow untrimmed for some time. Therefore, choose your planting material well. Look for young trees of approximately the same age, form and height to get the best looking hedge. It is important the hedge is pruned properly, especially in its first year.
Pinch the current year`s growth (“candles”) by a third or two thirds in late May or early June, before the needles break into growth. This will restrain growth of the pines, and they will grow more compact. Shorten only the branches, which need to be restricted. Such method of pruning can be applied every year. In order to stop the branch altogether, pinch the terminal bud in autumn, leaving the adjacent lateral buds, as they will grow into next years shoots. And other way round, the branch will grow faster after the lateral buds have been removed.
Bear in mind, that if all of the buds or the growing tip of the branch are removed, it will completely stop growing. In a few years time this branch will shed all needles and the tree will be left with a dead branch and a “hole” in the crown, when the branch will be removed. This might also happen, if the only bud on the branch is removed (side branches of mountain pines (Pinus mugo) and Japanese stone pines (Pinus pumila) usually have a single bud.
One does not need secateurs to train pines, unless for the purpose of removing the bottom branches of a young tree, when you intend to raise the crown of the tree, or if you need to prune a grafted standard pine, which still has branches of understock attached. These branches feed the grafted plant, until it matures, but later they are removed one by one, rather than lopping them all off in one go.
Training of the other species of pines is similar. However, a Scots pine (Pinus sylvestris) or an eastern white pine (Pinus strobus) will never take well to shaping into a cone or a ball, while a Japanese white pine (Pinus parviflora) will never grow to make a dense tree, like a Korean pine (Pinus koreaana) would. Pines are a perfect subject for bonsai training, but they have to be started young. This is an occupation for the most persevering, since it will take another 10 years before some results will show.
Pines dislike their branches being cut or shortened. If you want to remove a branch, then the cut should be made flush with the trunk. Do not prune out more than one or two branches a year. Best time to remove them is in summer (July, August), when weather is warm and dry. Remove dead bottom branches at the same time. The die-back of the lowest branches of pines is a natural process – this may happen when the tree is dense and the light does not get to the bottom branches, or when the plant is growing fast and its crown grows higher. Just like all the other conifers, pines should not be pruned in late winter or early spring.
© Giedra Bartas, 2009