Light and pH critical for plant combination success

Tom Dudek, Mich. St. Univ. Extension district horticulture and marketing agent, advises growers to follow two rules when selecting plants for mixed containers or hanging baskets.
1. Make sure the plants selected are appropriate for the location in which the container or basket will be displayed. Choose plants that fit their sun or shade requirements. Don’t mix light requirements. Check supplier culture guides for details.
2. Know the growing medium pH requirements of the plants. Don’t mix plants that have two completely different pH requirements. For example, calibrachoa grow best in a growing medium with a pH of 5.5 to 5.8. An inter-specific geranium or a zonal geranium grows best in a medium pH of 6.0 to 6.5. Putting these plants in the same combination results in one healthy and one unhealthy plant.
Fertilizing with an acid-based fertilizer (i.e., 20-5-20 or 20-10-20) to maintain healthy, low-pH plants harms those plants that grow best at a higher pH. Conversely, acid-loving combination plants fed with alkaline fertilizers can develop chlorosis.
Don’t let untrained staff put combinations together because they combine plants based only on their aesthetics.

Pictured: Don’t mix plants in combinations that have two completely different pH requirements.
Photo courtesy of Mich. St. Univ. Extension