Ideally, plants should be watered with room temperature water. However, watering some house plants, such as ficuses, with hot water can revive them back to health. If the young shoots located at the bottom of your plant begin to yellow and the leaves are wilted and have black spots, your plant’s demise may be caused by excess acid. Rather than repotting your plant, French horticulturalist M. Willermoz reported in the “Journal de la Societe d' Horticulture Pratique du Rhonek” that using hot water to flush out the excess acid can be just as effective as repotting.
Take your plant to an area where excess water can freely drain out, such as a sink or outdoors.
Water the plant with water that is approximately 145 degrees Fahrenheit. Measure the water temperature with a cooking or kitchen thermometer, available where kitchen gadgets are sold. Many hot water heaters heat water up this hot, but you might need to heat the water up on the stove in a pot if yours does not.
Watch the water as it drains. It will be clear at first, then slightly brown. Water for an additional minute to rinse out more acid.
Set the plant in a warm area, such as near a radiator or stove for about a week. The wait for the yellow parts of your plants to turn green and the black spots to stop spreading.