Use a liquid plant food every couple of weeks, especially if it’s been rainy or really hot: Lots of rain can wash away nutrients and temperatures above 95 degrees F slow growth.
You may need to stake taller varieties, especially the cockscomb types with their heavy blooms. Push a bamboo stake in the ground within a few inches of the stem at planting time and attach it with a piece of twine in a figure-eight pattern as it grows.