how early can you plant geraniums outside
3. Fertilize your geraniums once a month using a liquid fertilizer. An abundance of fertilizer will cause your geraniums to produce many strong, healthy leaves, but it will also prevent blooms from developing and may lead to a plant with minimal flowering. 1  You can also use a slow-release, granular fertilizer.tart geraniums from seed indoors. Early to mid-April is usually standard. Once the seeds start to sprout, you can move them outdoors. Just make sure that the last frost of the season has already passed.