Gardening Tips: August 28, 2013
It seems like we are about two weeks ahead of “normal” in terms of phenology this summer. “Phenology” is a term that refers to the timing and sequence of bloom of various plants that we can observe each season. It is a useful concept that predicts seasonal events based on what is currently occurring.
For example, gypsy moth eggs generally hatch each spring when the leaves on oak trees are about the size of a mouse’s ear. Crabgrass seeds begin to germinate when Forsythia is coming into bloom and so on. As useful as this term is, it has been pretty much replaced by “growing degree days” which is a bit more scientific. Growing degree days is a number that is calculated every day in which the temperature is higher than 50 degrees. The high temperature for the day and added to the low temperature and divided by 2. Any number above 50 adds growing degree days. For example, if the high temperature is 80 and the low is 60, then 80 + 60 = 140 divided by 2 = 70. 70 minus 50 = 20. Therefore on that day, we accumulated 20 Growing degree days.
Over the course of the growing season we can predict the occurrence of things, like certain pest insects hatching, based on GDD. This is an important part of Integrated Pest Management and can significantly reduce pesticide use. If we know that a particular pest hatches only after 200 GDD’s, we can withhold spraying until that number has been achieved. This idea replaces or reduces relying on calendar dates which seem to change every season.
The past two weeks have featured temperatures much cooler than “normal” for August but the July heat wave we had last month has resulted in so many GDD’s, that we are still ahead of “normal”. I don’t keep track of GDD but I sure do observe phenology and right now I am observing September events. Most notably is the blooming of a beautiful vine called Sweet Autumn Clematis, which is also called Virgin’s Bower. This vine features loads of small, white flowers and it often covers small shrubs or it climbs up utility poles. I have also observed wild apples ripening and dropping about two weeks ahead of usual and two weeks ago, I was followed around in the forest by far more adult, male gypsy moths that I care to see. I hope we are not in the beginning stages of another gypsy moth outbreak. These leaf eating caterpillars devastated the Catskill region back in the late 1970s and again in the late 1980s.
It was just a few years ago that we had to deal with an outbreak of forest tent caterpillars and our forests are just now rebounding from that cycle. Oddly, I am a gypsy moth magnet and these moths follow me in the woods, constantly trying to land on me. I believe this is because of the many years that I set out pheromone traps to monitor gypsy moth populations. Somehow their pheromone (sex lure) has become part of my body chemistry and I must smell like a female gypsy moth. Oh well, there are worse things to smell like and humans cannot detect the moth pheromone anyway. At least I hope not!
Here come the tomatoes
To a certain extent, GDD’s determine when tomatoes ripen and mine are coming on strong, I am happy to report! Soon I will be canning sauce and other tomato products. At the same time I am planting fall crops like beets, lettuce, radishes and spinach in anticipation of a long fall season. The days are getting noticeably shorter and the Katydids are announcing the approach of fall weather. On cool nights their call slows to a cadence that allows you to locate individual insects pretty easily with a little investigation. Lightning bugs have diminished but stinging insect populations are peaking.
As I get older, the sequence and cycle of nature becomes far more apparent than it was even ten years ago. This is a blessing and a curse, because as much as I appreciate the awareness of the Great Mandela, I am saddened by the knowledge that the remaining trips I have on it are diminishing much too quickly. The lyrics of a very popular song from decades ago “It’s a long, long time between May and December, but the days grow short, when you reach September” refer to more than phenology.