Dakota Gardener: The myth of high phosphorus fertilizers for more flowers

In my youth, I worked for a well-known Minnesota garden center. My co-workers and I would be frequently asked why a customer’s dahlia, geranium or other prized ornamental plant wasn’t blooming. Without fail, we would sell the customer a high phosphorus fertilizer to stimulate flower production.

In my current position as a North Dakota State University Extension horticulture specialist, my...