Soil is important when preparing your beds for annual color. You cannot plant in clay or normal landscape mix. Make sure the area where you are installing color is mounded up to present the color better, which also allows plenty of room for the root system to grow. In regards to drainage, when using a normal compost, it tends to clump up and hinder the roots. We suggest using a compost that is cut with white beach sand. This ensures proper drainage. Poor drainage can result in wet roots/disease in your annual color. So be sure to add some soil and mound it up when installing your annual color. We hope this helps, and check out our Knowledge Base for more tips: https://matthewslandscape.com/search