We are all familiar with dormancy in deciduous trees during the winter but we don’t think of it happening in the summer. We are used to the norm: as the fall approaches and light diminishes and temperatures drop, the tree will go into a dormant period that lasts until the spring arrives. During the winter metabolism decreases and the leaves fall to the ground, but a low rate of metabolism is still maintained until spring. 

The key to dormancy seems to be the production of abscisic acid (ABA), a plant hormone. When ABA is first produced by the plant in fall, dormancy begins. This condition stays with the plant all winter, as does the hormone. With the coming of spring, the acid breaks up and the plant comes out of dormancy. 

However a plant can also go into dormancy to survive drought or an insect infestation. By shedding it’s leaves it reduces transpiration or water loss. Again the dormant stage is triggered by production of ABA, which can be produced as a reaction to plant stress, according to Kimball’s Biology Pages.  Many times the tree will stay dormant until the following spring and will regain health, provided the drought or disease outbreak does not continue. 

In some situations, such as breaking the drought by irrigating, you in effect can start spring all over again!  The tree in the picture is a 5 year old European pear which has had no supplemental water since June, 2010.     

We all know the drought we have been and still are in, very little snowfall and until a few weeks ago we only had about ½” precipitation since January 1, 2011.  The few little monsoon rains we have had this last few weeks tricked this tree into believing it was springtime again.  With this hormone break-up it sprouted leaves and even started blooming!  The key feature for us to note is that obviously this is a tremendous rootstock for pears in New Mexico, being well suited to living through the droughts, and will be the variety we would use most for grafting pears.

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