Monday, July 16, 2012

Signs of plant drought (heat) stress

Evidence of heat and drought stress is now clearly seen on plant material here in the GTA.  This heat wave since June is taking its toll. What little snow we had over winter, and with our unusual warm spring - trees, shrubs, evergreens and perennials now bear the brunt of this drought.
Brown grass under tree (with fallen tree leaves)

Working in gardens every day, the signs are quite noticeable in advance, yet at my part-time garden centre job, customers bring in samples - not realizing the damage is from drought.

This baffles me.  I figure, if the lawn is yellow and gone dormant, don't you think the heat will have an effect on your other plants?

Please, water DEEPLY about once or twice a week, rather than each night with your hose end sprayer. Leave a sprinkler on for at least 2 hours in the morning. Leave a cup out under the sprinkler to see if it fills half way. The cup is a good indicator that at least 2 inches of moisture will go down deep, where roots are needing it.

Aerate your beds by giving them a good light scratch, so moisture doesn't run off the soil that has been baked to a hard crust. A good cultivation will allow the water to absorb more quickly.

For trees, take a garden fork and jab all around the drip line of the tree to aerate the area beneath. This will help water to penetrate down to the tree's fibrous roots.

Drip-line of tree
Interior yellowing of leaves on Tilia cordata
Curled leaves on Prunus Shubert Chokecherry
 A good 4inch layer of mulch around the drip-line of trees is a good practice. Especially for newly planted or establishing trees. Just be sure not to mulch the area around the trunk. Keep that area free, so the mulch won't rot bark. (Just think of a wet band-aid around your finger...:)

Some tell-tale signs of heat stress:
  • curled leaves
  • dropping leaves
  • yellowing interior foliage
  • dropping fruit
  • bud drop (on late flowering Rose of Sharon)
  • burnt edges
  • heavy seeding
  • insect infestations
  • speckling on foliage



Scorched Hosta leaves

Burnt edges on Brunnera



Over abundance of seeds on this Acer negundo















I can't stress enough regarding watering. Even with the thunderstorms and intense rain for a few minutes we had last night, the water would not of penetrated deeply enough for roots after such a lengthy dry period. It just runs off down the sewers.




Everyone wants a green lawn. Instead, focus your watering on trees and shrubs and less on the lawn. After a good rain or so, the lawn will bounce back quickly. Trees and shrubs won't. They need our HELP!

Remember:  A fully grown tree may lose several hundred litres of water through its leaves on a hot, dry day. The same tree will lose nearly no water on wet, cold, winter days. Almost all water that enters a tree's roots is lost to the atmosphere but the 10% that remains keeps the living tree system healthy and maintains growth.

Water, water...water!

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