Colin Lewis

I missed the brginning of this thread, but from what you say it seems you are getting exactly the same results as I did. In the early nineties, when I was publishing the UK Bonsai Magazine (now a part of Bonsai Europe) I ran some fairly scientific tests.

I got five other people, as well as myself, to grow scots pine and larch seedlings and elm cuttings in several different soil types. Two of the five had no horticultural experience. Soil types included akadama, peat, turface, garden soil and sand - plus a fairly standard bonsai mix. Everyone grew one of each species in each soil type - eighteen plants each. All were foliar fed only.

With no exceptions, peat stimulated the most prolific roots and largest plants. Sand gave a lot of root growth but slightly less bio mass. Next came akadama, turface and finally garden soil.

This is how seedling roots behave after one season, but that does not mean the same would happen year on year, or with older more sedate trees.

I believe this result has to do not so much with the moisture retention properties of the soils (sand holds little) but more with how available the moisture is to the roots. Peat and sand are both very fine with tiny interparticle spaces. Wherever roots want to go they can and they will always be in contact with available water.

Fast forward a few years to a nursery plant growing in pure peat-based compost, and you're potting it down. The roots are very fine indeed and they form a dense block that is impossible to comb out - right? That's the problem with peat as a long-term growing medium.

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COLIN LEWIS
www.bonsaideals.com
www.bonsaiforum.com