Answer: I hope by now your mimosa has recovered. Unfortunately, watering methods aren't always well communicated. When someone advises to give a newly planted shrub a lot of water, they really mean that you shouldn never let the soil dry out. Even, deep, consistent moisture is a better way to express it. If the soil is too soggy, it will impair root function. To test the depth of soil moisture, use a long, thin metal rod, like a long screwdriver. Poke the rod into the soil. When soil is moist, the rod will move easily through it. When the rod encounters a layer of dry soil, it will be hard to push. Water your tree so that the soil is moist to a depth of a foot and a foot or so beyond the root ball. The soil surface should not remain shiny or muddy, but should dry out a bit between waterings. By using the rod method, you'll learn how water behaves in your soil and can irrigate accordingly.
If you feel you've overwatered, just let the soil dry out a bit, and watch carefully for signs of recovery.
If you transplanted your to a pot or to the ground, then the yellowing leaves may also be evidence of root disturbance. If you planted your tree in an area where a mimosa has already succumbed to wilt, then the organism is probably in the soil, but symptoms of the disease would not show up immediately. There are varieties of mimosa that are resistant to the disease, too. I hope this information is helpful!
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