How can I tell if my rhododendron needs more water or less?

Check the moisture where the roots are, not just at the surface. If the root area is drying out, give it a slow, thorough watering and let excess water drain away. In warm weather, a plant can droop from lack of water even if it was watered recently.

If the soil is persistently soggy, or the roots look dark and feel soft or smell unpleasant, hold off on more water and check that the container or planting spot drains properly.

Rhododendrons generally do better with evenly moist soil, not a cycle of drying out completely and then being kept wet. Heat and fast-draining soil can make regular watering insufficient, while compact or poorly drained soil can leave roots short of air.

Check the root zone and drainage first. If water runs straight through and the soil quickly dries, watering more slowly or improving moisture retention may help. If it stays wet for a long time, more water is unlikely to solve the problem.

I would avoid a big rescue operation until you know what the roots are doing. If the plant is in a pot, make sure the drainage holes are open and the pot is not sitting in collected water. Only remove roots that are clearly dead or mushy, and do not strip healthy roots just because the leaves look rough.