Dorothy Koreshoff O.A.M. ©️ reproduction by permission.

I have spent what seems a lifetime with bonsai since marrying Vita Koreshoff in 1949 at the age of 18. He had been growing bonsai before I met him, but over the years, Vita and I trialled different techniques and ideas on many aspects of bonsai together. This series of articles relates our progress and discoveries pertaining to potting mixes.

These days bonsai growers and indeed gardeners in general, may wonder why a series of articles on potting mixes would be relevant, especially when you can easily pop into the local nursery, hardware or even grocery store and bring a bag of ready-made potting mix home. A few minutes later your bonsai is potted and you don’t think of the mix again until it’s the next time to repot. If only it was that easy in 1949.

Back then pre-made mixes were not available. Nurserymen and backyard growers had to make up their own ‘mix’. Container plants were mainly potted in soil that came straight from the grower’s back yard. As you can imagine, the soil varied greatly according to the grower’s location. Nurseries grew most of their stock directly in the ground. The plants would be dug up in winter and then the root ball was wrapped in damp hessian and sold this way. If the plants were sold in containers, they were usually in the old terracotta pots, which broke easily, were extremely heavy and very porous.

Some plants that we purchased from growers were in a soil that one could only describe as cement. The soil would be so compact that the water would sit on the surface and never drain. Even the broken pieces of terracotta pots, or ‘crock’ as they were commonly called, that were placed over the drainage holes to assist in drainage were of no use.

Vita was also growing plants in soil from our back yard. I call it soil, but really it was almost pure beach sand, as we were living just a short distance to the coast at the time. Vita tried various ways of introducing organic matter to the soil to overcome its poor quality. At first he added well rotted horse manure because it was readily available from local stables; this helped not only to hold water, but also acted as a form of fertiliser. The most widely available fertiliser that you could buy at the time was blood and bone. This was sparingly sprinkled on top once the tree was established.

This was the environment that our bonsai were grown in. It must be said that while we lost many trees during this period, we never lost any that could be directly attributed to the mix. However, we weren’t content that they were growing to their full potential. Over the next few articles I will describe our attempts to achieve this.