I have Three leaf sumac (2) as bonsai. Both are planted in a 25% peat moss an 75% sand mix. After potting all the leaves dried and fell off. The leaves stayed green but turned very brittle. A few weeks ago I noticed new growth. The second tree is exhibiting the same condition. Is this shock from being re-potted? I water both every other day. They get 30% sun light.
I am open to any suggestions.
Yes, that reaction is shock. You repotted them at the wrong time of year. Fortunately they are resilient enough to come back from such treatment. Next time, repot only in late winter, or early spring. BEFORE buds open to leaves. Once you see green coming out of the buds, it is too late.
A second repotting opportunity is about 2 to 3 weeks before the autumnal equinox. Last week of August or first week of September. This is not as ideal a time, but many have success.
Trees should be repotted as seldom as possible. Once every 2 or 3 years is the most. Don't repot, the mix you used is not that bad. Wait until 2021 to repot. The sand and peat moss is a "landscape nursery" style mix. It will be fine, if you are careful to water when it needs it.
In 2 years move your trees to a mix for bonsai that like acidic conditions. Kanuma would work. Read up on azalea potting mixes.
When my group was scouting locations for a blueberry farm (blueberry love acid soils) we looked for areas with Rhus typhina, (staghorn sumac) and Sassafras, when both are present, the combo indicates an acidic soil good for blueberries.
R. trifolius also likes acidic soil. Though because they are used in general landscaping, they are pretty forgiving if soil is not perfect.
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