Phenology: the Art of Reading Nature & Climate

Posted: May 17, 2011

Have you ever heard a gardener say to plant peas when the forsythia and daffodils begin to bloom, or to plant beets, potatoes, and carrots when dandelions begin to bloom?


This is called phenology, the relationship between climate and periodic reoccurrences in nature. It utilizes temperature (heat accumulation) instead of calendar dates to determine what’s going on in the garden.

Heat accumulation is measured by growing degree days (GDD), or growing degree units. This system is used by horticulturists, gardeners, and farmers in various ways, such as to correlate insect emergence and pest control; to correlate crop planting dates; or to predict when to apply fertilizers and pesticides. To find out more about GDD, visit

By using the concept of phenology, as a vegetable gardener you have enlisted another important tool for success in your garden. More importantly, you are paying attention to nature in addition to the calendar.

Some other examples of phenology are to plant beans, cucumbers, and squash when lilac is in full bloom; plant corn when apple blossoms start to fall; and seed cabbage and broccoli when catalpa and mockorange are in bloom.

For an example of pest management, the squash vine borer lays its eggs when chicory flowers are in bloom. That gives you the timing to know when to scout for and eliminate the eggs. And if you find yourself at all interested in this idea, an excellent book to consult is Coincide by Donald A. Orton.

Keep a garden diary and write down what is going on around you. Pay attention to what’s blooming and leafing out at the same time you are planting your vegetables; and note how well your crops do. It is the best way to get to know your garden. You’ll be pleased with your results and surprised to see how proficient you become in gardening. Most of all enjoy and have fun with your garden.

Nature can provide clues to timing events in the garden if you pay attention to  phenology, the relationship between climate and periodic occurrences in nature.