Growing Japanese Black Pines as bonsai is both rewarding and challenging, especially for those new to pines. In this exclusive interview, we sit down with Mark Polsen, an experienced bonsai grower, to uncover the secrets behind successfully developing these iconic trees. From seed to refinement, Mark breaks down the techniques, strategies, and timelines required to transform a young pine into a show-ready bonsai.
Starting from the very basics, Mark explains the critical first year of a pine’s life—how to properly plant and care for seeds, what soil mix to use, and when to repot seedlings for the best growth results. He also sheds light on the importance of Mycorrhiza, a beneficial fungus that plays a crucial role in a pine’s health, and how to ensure it remains in the soil when repotting.
Once past the seedling stage, the colander method comes into play, a widely used technique that encourages strong root development. Mark walks us through the best practices for transitioning pines from colanders to open-ground growing, explaining the advantages of planting on tiles or in perforated containers to enhance trunk thickening. If you’ve ever wondered how to accelerate trunk growth without sacrificing long-term structure, this part of the interview is essential.
Moving from development to refinement, Mark discusses the key techniques for creating a beautiful, compact bonsai, including needle work, shortening internodes, and promoting bifurcation. He shares his personal approach to fertilization—when to feed heavily, when to reduce nitrogen, and how to adjust your fertilizing strategy based on the tree’s stage of development. If you’ve ever questioned whether reducing nitrogen after needle pruning is better than stopping fertilization entirely, you’ll get your answer here!
One of the most frequently asked questions in the bonsai community is how long it takes to develop a Japanese Black Pine from seed. Mark provides a realistic timeline, outlining what to expect at each stage and how to speed up development while maintaining quality. Whether you’re just starting with pines or struggling with their slow growth, his advice will help you avoid common pitfalls and get the best results faster.