Potassium-softened water is actually good for your plants. Potassium is an essential plant nutrient that must be available in significant amounts in the soil to grow healthy plants. While you may have heard warnings against watering your garden plants with water softeners, those warnings only refer to sodium chloride water softeners. These softeners deposit excess salt into the soil that can dehydrate plants. Potassium-softened water is perfectly safe and can be applied to the garden like water from any other source.
Check the soil frequently. When the top inch or so of the soil dries out, it is time to water most garden plants. During excessively hot or dry periods, you may need to check the soil as often as twice daily.
Apply 1 inch of water to plants with average soil needs whenever the soil is dry. Install a rain gauge in your garden (available at most garden centers) to help you measure the amount of water you apply to your garden plants. Early morning, before the sun reaches its apex, is the best time to water.
Water houseplants with softened water that has been allowed to sit out overnight. Potted plants' limited soil is more susceptible to the residual hypochlorites and dissolved carbon dioxide in softened water. Letting it sit will allow these residuals to dissipate.
Contact your local county extension office to have a soil test conducted. The increased potassium level in your soil may change your garden plants' nutritional needs. The soil test will tell you the correct amount and type of fertilizer now needed for your plants.