These simple tips on trimming and pinching are from an extensive article entitled ‘How to Train Coniferous Bonsai’ from Bonsai Today issue 42. Stay posted for more tips from this article.
Books on the subject
Two of the best books on training conifers are part of our Masters’ Series: Growing and Styling Juniper Bonsai, and Growing and Styling Japanese White and Black Pines (most of the info is good for other pines).
Here’s another piece from the same Bonsai Today article. Pruning and pinching excess foliage are always a good idea when transplanting. Less foliage means less work for stressed roots (transplanting causes root stress, especially if you rootprune).
We transplant all summer
As far as the until June part (see above), here in Vermont we can transplant conifers all summer long because it seldom gets very hot. In fact, if you know what you are doing, you can transplant conifers all summer in all but the hottest and driest climates.