Friday, August 30, 2013

Evidence Of Drought Stress Is Everywhere Around Boston

Dogwood with classic drought stress symptoms with
crispy tips and edges to leaves.  ©2013BDG
We have have had an interesting summer in New England as far as rain and temperature goes, but it seems as though every year is interesting -- just in different ways.

The predominant issue coming into the fall is that we are low on precipitation, and it is worse than the numbers reveal because most of our rain has come in quick dumps or large sustained events.  

According to the Blue Hill Observatory, just south of Boston, we are 1" below the 30 year average for August, and all but a trace of this month's rain came in a storm in early August that dumped over 2" in a few hours.  These quick and hard rains almost never infiltrate to the plant roots as it tends to runoff faster than the soil can absorb it.  July was also below the 30 year average for rainfall. So, for the last two months our gardens have not been getting the water they need.

I am not making a political statement but it is hard to
dispute that man and the industrial age has had an
effect upon our climate.  ©Blue Hill Observatory
June was a statistical aberration coming in 8" above the 30 year average, yet over 10" of the 12" that fell in June came between June 9th and June 19th.  Then, as we all remember, came the brutal two week heat wave that stressed everything.  We had the 4th wettest June on record followed by the 3rd hottest July on record, and now that August is finishing we will have a warm weather month where the average temperature is below the 30 year average for the first time in the past three years.




So what does this all mean in the garden.  

Japanese Maple with crispy tips.  ©2013BDG
It means that our bigger plants and trees, that don't benefit from irrigation, are thirsty.  Many of the images here show plants with varying degrees of stress.  Burn't leaf edges, early leaf drop, contorted or sagging leaves are some of the clues.  Evergreen plants and trees do not show their stress until it is too late, so make sure you water them as well.

Irrigation systems are great for lawns, perennials and small shrubs.  They are designed to deliver water for plants and lawn that live in the top foot of the soil.  Our bigger plants and trees require water deeper in the soil and when it doesn't get replenished by deep soaking rains they suffer and it often doesn't show until subsequent seasons in large trees.  The only downfall to irrigation systems is that people can lose touch with their gardens.  Sure you don't have to go out and move the sprinkler every couple of hours, but with a system, people often assume everything is OK.

Birches are plants from the riparian
zone and need lots of water.  They
are often the first to show drought
stress.  ©2013BDG
I have been out in my garden over the past weeks and I am telling clients and friends to put a hose at the base of their ornamental trees and bigger plants and let water trickle into the root zone for a few hours(depending upon the size of the plant).  Turn the hose on so it flows well, but not very strongly, and place it a foot or two away from the trunk of your shrub or tree.  Let the water flow for an hour or two.   A big (15-20') Dogwood or Japanese Maple would love 2-3 hours and move the hose around once or twice during the time so a broad area of the root zone gets moisture.  Younger and smaller plants only need an hour or so to replenish moisture in the root zone.  Set a kitchen timer to remind yourself to move the hose.

So what plants really need watering.  All of your ornamental trees (evergreen and deciduous) will benefit as well as any tree that was planted less than five years ago.  Large shrubs that may get limited or no irrigation like Lilacs, Viburnum or Holly as examples.

Leaf litter is a sure sign that something is stressed.  Look
up to find out what is happening.  ©2013BDG
Standing with a hose and watering for a minute or two will cause more harm than good as it will force the roots to grow close to the surface for water making them worse off during times of drought.  A great rule of thumb for all watering (including the lawn) is to water deeply and less often.  If your irrigation system comes on every day you should talk to someone knowledgeable about adjusting it (and saving money).

A lot of people talk about using native plants in gardens as they are better adapted to our local temperature and precipitation patterns, among many other good reasons, but when you have significant variations in weather, even natives are not immune to drought.  A plant that is native in New England still needs an inch of water a week to be happy.

Lawn without irrigation is not doing well.  It has gone
dormant and will come back in the fall, but some water
will make sure it doesn't die.  ©2013 BDG
So get out there and give your ornamentals a drink.  Don't let them go into the fall and winter stressed from lack of moisture or they will not perform well or die in subsequent years.  One good soak over the next week or two will set them up well for the fall provided we get back on track with rainfall.






Rhododendrons are shallow-rooted and stress easily.
This will look great two hours after being
watered. ©2013 BDG







4 comments:

  1. After such a wet spring it is difficult to endure an August drought! Gardeners need to be so very stoic. Thanks for bringing the drought to our attention.

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    1. Of course, the moment I post a watering concern we get the storm of the year. Maybe I should remember this in future years when we need water to write about it.

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  2. So true Reed and a very insightful observation about irrigation systems making gardeners less in touch with what's really going on in their gardens. Compared with the perennials or even lawns that we lavish our attention and water on, trees and large shrubs that die take years to replace, and with them goes that mass and structure that's so important in good garden design.

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  3. We're dry here, too, although not as dry as you are. We had tons of rain in June/July but August has been much drier. When we're really dry, I run my soaker hoses for hours since many of the plants in my garden also compete for moisture with mature trees. I end up with huge water bills but a happy garden. :o)

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