What’s wrong with my flowering plants? They aren’t growing like they should and/or they’re not flowering. That’s what my friends who work in garden centers and nurseries are hearing from their customers this year. In most cases it’s the weather. Our ever-changing climate is playing havoc with the annual flowering plants we grow in pots and planting beds and folks who grow and sell these plants can’t do anything about it.
This spring, cold wet weather persisted several weeks into the planting season and in spite of advice to the contrary many homeowners failed to heed the warnings and planted up their gardens and pots with the tender flowering plants we call annuals. When temperatures dipped into the 40s at night and damp soils remained below the recommended 60 degrees these plants need to thrive, they sulked. No amount of fertilizer would make them budge and in some cases they became permanently stunted.
But when the weather finally warmed up, almost overnight the temperatures climbed into the high 80s and even the 90s. Our lovely spring rains all but disappeared. The sudden onslaught of abnormally high temperatures and drought along with drying winds so early in the growing season caused many of our tender annuals that just started growing to shut down. Many plants just go dormant in hot dry weather to conserve energy and moisture, and that’s exactly what happened in many gardens.
Fertilizing plants when it’s hot and dry is a no-no. The cut off for me is 85 degrees. So my annuals in the OPC garden in Rochester were not fertilized until a couple of weeks ago when we had a blessed daylong rain and temperature were in the 70s.
There is no such thing as one size fits all when it comes to fertilizing. Some plants, such as petunias and million bells, are heavy feeders and should be fertilized with a full-strength formula every 7-14 days. Low feeders, such as New Guinea impatiens, do best on half strength. If you fertilize your annuals with every watering, use1/4 the strength recommended on the container, but back off during a heat wave.
With the exception of a few heavy feeders, such as Delphinium, I do not fertilize perennials during the growing season. A dusting of compost on the surface of the soil in fall or spring and possibly a light sprinkling of a granular organic fertilizer will do. Most Xeric and native plants should not be fertilized.
Nancy Szerlag is a master gardener and a Metro Detroit freelance writer. Her column appears Fridays in Homestyle. To ask her a question go to Yardener.com and click on Ask Nancy. You can also read her previous columns at detroitnews.com/homestyle.