Lady Baltimore Hibiscus plants need plenty of nutrients to thrive. There are a few ways you can fertilize your plants. The first option is to fertilize in the spring by adding a layer of compost around the base of your plant. Or you can apply a 10-10-10 fertilizer around the base. However, be careful not to add too much fertilizer around your plants. Too much fertilizer will contain too much phosphorous and can kill Hibiscus perennials. There is no need to fertilize your plants in the winter during their dormancy period.