There’s no mistaking the colour and stature of annual Zinnias.Follow this handy How to Grow Zinnias from seeds guide below and grow some colour in your garden this summer. Plant Zinnias seeds in average, well-drained garden soil, but dig in a generous amount of well-rotted manure the previous fall. Pinch off growing tips early in the season for bushier growth. Water regularly, keeping leaves as dry as possible. Deadhead regularly. Feed once in early spring, and again once flowering has begun.