Cassia Nodosa Is Rotting

Question

3rd day after planting from pot to garden the plant started dropping n leaves are turning brown showing signs of wilting

Answer 1

It sounds like the soil is, either, too wet or infected. The roots could have been disturbed with the transplant, as well. This collection of articles will offer more information on Cassias:

https://www.gardeningknowhow.com/ornamental/trees/cassia