Tuesday, March 27, 2012

Phenology in the Garden

Bulbs, mostly from plants that originally grew in snowy alpine regions, can handle the vicissitudes of spring and provide welcome colors to northern climates in early spring!

Spring Update:
Spring is rapidly proceeding across the country, with high temperatures still breaking records in much of the northern US. Here in the Rockies plants are blooming an average of 2-4 weeks earlier than normal. The dry La Nina winter has been warm and dry in the Colorado Front Range, leading to a series of fires this last week and early but not lush vegetation growth. Black bears are already coming out of hibernation! Just this last week tulips, grape hyacinths and other garden bulbs have started flowering, green ashes are in bloom now and crabapples and plums are covered with white or pinkish blooms. Forsythia is in full bloom now. All are about 3 weeks early this year. We are having day after day of temperatures in the 70's or even 80's, whereas normal is closer to 50-60 degrees.

Cherry Blossom Blitz: Reports are beginning to trickle in of chokecherries, sweet cherries, and Japanese cherries beginning to bud out or to bloom, first in the south, but more in northern areas as well. In my yard the sweet cherries and the chokecherries have swelling buds this week. Every day new plants become active -- its the best time of the year to be watching plants!

Phenology in the Garden
This time of the year, as garden soils are thawing out, and budding plants are everywhere it's a good time to consider another value to knowing when plants start budding out or sending out their first flowers. Phenology is an ancient science, and was practiced long before there was much scientific understanding of what clues plants use to determine when to start their spring growth. For early agriculturists it was a matter of survival. Phenology was used to determine when to plant crops, and to time other activities on farms or ranches.

For gardeners and homeowners today phenology can be used to determine when to start various treatments in lawns or gardens, and are much more accurate than using some general date on the calendar. For example when Forsythia is in bloom is often used to indicate when to start worrying about treating weed seeds in lawns. Soils need to reach about 35 degrees before seeds of lettuce and onion may be expected to germinate. This temperature can be determined by which species of wildflower are active. Flowering of dandelions can be used to estimate this time period. Some other examples of how phenology can be used in the garden:
plant potatoes when dandelions are in bloom
transplant melons and peppers when irises are in bloom
plant tomatoes when lily of the valley (Convallaria majalis) is in full bloom.

Of course like a lot of hints provided to complex phenomena in nature the devil is in the details. These rules of thumb vary depending on where you live, and the specifics of your home or garden. But you can see that if you keep careful records on the phenology of your garden as well as wilder places around you, you can develop your own rules for when to do various tasks in the yard or garden. As our weather and climate continues to gyrate wildly from year to year these clues may become a lot more useful than the typical generic guidelines you see in gardening publications.

Project Budburst is all about becoming closely connected with and in touch with your local environment. This knowledge can have practical advantages too!

Paul Alaback

More examples of garden phenology

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