Sunday, September 11, 2011

Repotting of a Japanese black pine

Hand and Gerdi own this most impressive Japanese black pine (Pinus thunbergiana) on a rock since a few weeks. When the tree arrived it looked very dark green and not so happy as seen on the first image. I found that the soil surface was hard like cement. Hans could not water it easily. When watered the water would just drop of the moss and not really go into the pot. Same with liquid fertilizing. So Hans watereed it carefully several times until the apparently dry lower part of the soil became moist. Then somehow water could go through the moss. He also fed it with koi pond water. After six weeks the tree looks much healthier. But the cement like soil really bothered us. So we decided to repot it now. It turned out that 2.5 cm (one inch) of the upper part of soil were solid like cement. Below as good very coarse substrate with almost no organic content. So we carefully removed almost all of this poor soil. We just loosened the root ball a bit and did not bother the roots really or cut off. Well, we did cut off a couple very small roots on top which did not help the nebari to look powerful Then modern subtrate, in this case baked loam with 20 % very rough peat was filled in. The tree was placed on the post again and will be watered and fed just like all the other trees right away. I think it has a bright future now. One day we might turn the tree with rock three hourss counter clock wise and have a new front which seems to me will look better.
The big and most impressive Japanese white pine (Pinus parviflora) of Hans has the same problems but not to the extent as the black pine had. So we decied to postopone repotting to end of April 2012. Spring is better than fall in our climate where it can get quite cold.