We generally do not recommend watering plants with softened water, due to the sodium levels. Soduim can dehydrate plants and trick them into thinking they absorbed more water than they have. This is also important to keep in mind when installing the drain hose on your system - keep recharge drainage water clear of your grass, gardens, flower beds, etc.
If you are using an alternative Potassium Chloride (KCl) salt pellet in your softener, you may wish to research the plant type specifically. Some plants recieve potassium well, but too much can be detrimental to certain species.