Soil and repotting
One principle governs everything in a tropical climate: the mix must drain fast. Monsoon rainfall will destroy a blend that works perfectly well elsewhere.
The mix we use
- About 60% granular, porous material — pumice, or akadama where available.
- About 25% coarse sand or fine gravel for drainage.
- About 15% organic matter — fine pine bark or coco peat, no more.
For costalis, drop the organic fraction to around 10%. It is the most root-rot prone of the three.
When to repot
Without dormancy the trigger is the tree, not the month. Repot when roots have filled the pot and water begins to sit on the surface — typically every two to three years for young trees, three to five for finished ones.
The start of the wet season is safest, because recovery is quick. Avoid repotting at the height of the dry season.
Root pruning
- Remove at most a third of the root mass in any one repot.
- Keep as much fine root as possible; that is what takes up water.
- Move to partial shade for two to three weeks afterwards.
- Do not feed until new growth appears.