While most commercial production facilities identify and correct pH-induced nutrient disorders before product is shipped for finishing or retail, some issues still crop up once plants reach their final destination. Two issues commonly seen at the retail level are iron and manganese toxicity in zonal geranium from low media pH and iron deficiency in calibrachoa from high media pH.
According to Beth Scheckelhoff, educator at Ohio State University, it is important to make sure all garden center employees are trained to keep an eye out for plants that begin to look a little “off” from surrounding plants or other cultivars of the same species. Suspect plants may show discoloration, leaf or flower deformations, overall stunting, or other abnormal characteristics. These plants can indicate larger issues with plant nutrition, the environment, or pests.
"One of the most inexpensive devices a greenhouse or garden can invest in is a handheld pH meter. This is a must for every greenhouse and garden center and will easily pay for itself over a short period of time," Scheckelhoff explains.
A recent visit to a retail establishment identified two separate issues in close proximity. First, zonal geraniums were suspected to have a root pathogen as one variety discolored foliage and browning of leaf edges. Inspection of the root system showed healthy roots concentrated at the bottom of the containers and not throughout the growing media. Foliage discoloration was uniform across a handful of plants and beginning to show throughout additional plants in the greenhouse – though only in this one cultivar. A pour-thru media sample showed the pH to be at 4.8, well below the desired range of 5.8 to 6.4 for zonals.