Statistics are useful ways to analyze data, but they can also be misleading. This summer is a classic example of how numbers do not tell the true story. We went for weeks without any significant rain, coupled with extreme heat, which has caused fairly extensive mortality on trees and shrubs. Even trees that have not died outright may have been permanently damaged by the hot, dry, conditions. It will take years for some sensitive forest tree species, such as hemlocks, to recover. Yet, when the drought finally ended, as it has for most of the region, with as much as six or seven inches of rain falling in just a few days, the total rainfall will probably make this an “average” season, in terms of total precipitation. In terms of temperature, it only takes a few cold nights to “average” out the 20+ days over 90 degrees.
We all know that this has been a far from average growing season. Soils are capable of retaining only a certain amount of moisture. This is called “field capacity.” Once the soil is at field capacity, any additional rainfall either runs off, washing away some of the soil, or it puddles, creating a low oxygen condition that may suffocate roots. Soils that have a lot of clay are capable of storing much more water than sandy soils. In a dry summer, such as this, plants growing on clay soils have fared far better than plants growing in sandy soils. Just as one cannot “catch up” on sleep, by sleeping for 12 hours, after several days of four hours of sleep, our soils cannot “catch up” from a moisture deficit when we get several inches of rain in a hurry. The best we can do is to store the excess water in rain barrels and other containers for future use. Two weeks of no rain will negate any value from the previous downpours. You still need to water newly planted trees and shrubs weekly, in the absence of at least an inch of rain.