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Monday, September 19, 2016

Still dry

As of September 1, most of Massachusetts is officially suffering from severe to extreme drought conditions. How are plants and people coping with the drought?

    What I see happening to plants around town is sad and alarming. Leaves of some trees have turned completely brown and dropped off early

A pin oak (Quercus palustris) cuts its losses

Sometimes it’s hard to see why one tree or shrub is suffering, while another nearby seems to be relatively unscathed.

    The reactions of two hydrangeas about ten feet apart in my front yard are puzzlingly different. One wilts almost every day, has dropped all leaves from some branches, and looks as if it’s near death, despite my watering efforts. 

This hydrangea can't catch a break

The other is still just as perky as it was this spring, holding its bright green leaves up to the sun as if there were no problem at all.

This one is doing fine

    I went to the Internet to find out what’s going on. North Carolina’s Cooperative Extension provides a useful article on plants’ response to drought. The author, Barbara Fair, PhD, explains that when plants can’t get water from the soil, they go into crisis mode, jettisoning important functions. Wilting, letting leaves hang vertically when not enough water comes from the roots, changes the angle at which the sun’s rays strike the leaves, reducing water loss. 

     In these conditions plants send chemical signals to their leaves to close stomata, pores that let water out. If the stomata stay closed too long, preventing evaporation and water flow through plant tissues, the plant can suffer from both over-heating and nutrient deficiency.

    Next desperate measures include sacrificing some leaves, twigs or branches to save energy and stopping production of chemicals that protect the plant from attack by insects, fungi and bacterial diseases.

This horse chestnut (Aesculus hippocastanum) prioritized making seeds over saving leaves

    My hydrangea’s problems could be multifactorial. It may be an especially thirsty cultivar. It may be in a slightly hotter, sunnier, or better drained spot than its compatriot, though both are in part shade. Roots of a nearby oak could be capturing the minimal water available, leaving the drooping hydrangea dry.  The shrub could even be suffering from a wilt disease, to which drought stress makes it more susceptible. 

    The drought response of the people around me varies. A valiant member of the Holden Garden Club, faced with an outdoor watering ban, has been collecting the not-yet-hot water from her shower in a bucket for her plants. Meanwhile, neighbors in my city, under no watering ban, are proceeding with sprinkling newly seeded lawns as if there were no drought. 

Watering during sunny days maximizes loss to evaporation

    I’m no water hero either. I’ve stopped squandering water on my lawn, but I’ve continued irrigating garden beds—less often--and watering container plants by hand. As the drought drags on, I too have resorted to saving water from indoors for some thirsty plants. In my case it’s rinse water from the kitchen sink. 

     While I think reseeding a lawn right now is going too far, I can sympathize with the impulse. It’s hard to watch your garden dry up and die.

Late-breaking news--it rained today! The water barrel is filling up at last.

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