The following is a good article on care of plants in a retail setting from the New England Greenhouse Update.
Plants on display in your garden center or farm stand require regular, gentle watering to maintain high quality. Watering should be completed during the daylight hours, to allow plants to dry before dark. The drying will help prevent foliar diseases. If plants are to be watered by hand, be sure to furnish sufficient time and personnel to water thoroughly. Anything less, and plant quality will decline rapidly.
Place hanging baskets in areas beside the aisles, not over aisles where water and fertilizer will drip onto customers and create a hazard.
Keep plants and surrounding areas in order and clean even during the busiest times. Removing dead and injured plants and spent flowers are essential at least twice a day even during the busy season. Customers get turned off when plants look bad and high ethylene concentrations from decaying plant tissue will causes premature loss of foliage and flowers. A skilled employee isn’t necessary for these jobs, but a competent one is. Employees should carry pruning shears and wear work aprons with large pockets where they can keep dead flowers and debris from plants in the sales area until they can find a waste can.
Plants in hanging baskets and planters will stay in those containers throughout the summer and will need to be fertilized in a retail operation. Depending on the plants, options include fertilizing on a weekly basis, using 400 ppm N or 200 ppm N at every watering or topdressing with a controlled- release fertilizer according to directions. Retailers should communicate with their wholesale growers to make sure controlled-release fertilizer has not already been applied prior to shipping.
Potted plants and bedding plants left over after the busy weekend will also need fertilizing, especially if they have been irrigated and spot watered with only plain water for several days. Inspect the root health and if healthy, fertilize, using 200 ppm N. Poor root health may indicate a need for a fungicide application.
Article by Paul Lopes, University of Massachusetts and Tina Smith, University of Massachusetts in the current New England Greenhouse Update http://www.negreenhouseupdate.info/greenhouse_update/index.php