Practical phenology

The warm days we experienced over the winter felt heavenly to us, but to the plants, insects and other animals that depend on each other, they were not so wonderful. Phenology measures recurring things that happen in nature (like a specific type of tree blooming) and compares it to the number of "growing degree days (GDD)" that have accumulated since Jan. 1. GDD are essentially a measure of accumulated heat, by a somewhat complicated formula. There is a calendar online that will tell you how many GDD we have so far this year, and what is going to bloom or hatch next. The number of GDD on a certain day vary year to year. On April 6, 2023, we had 91 GDD; while on April 6, 2020, we had only 64. This tells us that the Cornelian Cherry Dogwood, which hits full bloom at 98 GDD, will bloom much earlier this year than it did in 2020. The trend is upward— higher GDD at earlier calendar dates. According to Corinna Riginos, the director of science at The Nature Conservancy Wyoming, "Plants change their flowering dates in response to the climate, but many species of insects and birds time their emergence or migration on day length." Smaller cold-blooded animals like insects can change their phenology much faster than larger animals like birds. This causes a mismatch between plants, insects and animals that can have devastating effects. A too-warm early spring can cause butterfly larvae to emerge earlier than their host plant is available to them, sometimes wiping out an entire local population. We can't change day length. We can't, by ourselves, stop climate change. Is there anything a gardener can do to help minimize the effects of this phenology mismatch and try to support the ecosystem at home? Here are some suggestions for helpful strategies — you might just plant the one plant that saves a local population of a bird or butterfly! Plant to increase diversity. In any population, there will be some plants that manage to survive stressful conditions better than others. The strong will survive and reproduce. To this end, planting a "straight" species that has more genetic diversity than an inbred cultivar may be helpful. Try to smooth out the extremes; early frosts and hot dry spells cause the problems, not the averages. Use mulch to cool the soil and retain moisture. Plant a windbreak. Provide drainage, and save the water for later use. Use cover crops. Experiment with plants known to thrive in slightly warmer zones, but avoid invasive ornamentals. Choose plants that can feed caterpillars and help perpetuate the food cycle. (National Wildlife Federation has a great site for this.) Plant natives — they tend to have deeper roots, need less water, and sequester more carbon than cultivated ornamentals. Native grasses have particularly deep roots that stabilize soil and prevent erosion. The more diverse your plantings, the better chance that some of them will survive odd weather and be available for the birds, insects, and other wildlife that come looking for them. If we all do a little, it can add up to a lot! For more information, visit: • weather.cfaes.osu.edu/ gdd/calendarview.asp • nwf.org/NativePlantFinder/Plants