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10 Neat Things About Trees in Spring
by Dorothy Dobbie
by Dorothy Dobbie

The Local Gardener magazines, Ontario Gardener, Manitoba Gardener and Alberta Gardener, are published by Pegasus Publications Inc.

Drawing on her 30 years' experience as a senior executive in the magazine publishing industry, Dorothy launched Manitoba Gardener in 1998, initially running the business out of her home. Two years later, Dorothy's daughter Shauna, living in Ontario, jumped into the fray with Ontario Gardener. And two years after that, they started Alberta Gardener. Visit us at and register for our "Ten Neat things" newsletter. Watch Shaw TV for garden tips and Listen to CJOB for the Gardener Sundays at 9:08

April 25, 2021

1. I’m not sleeping. I’m just resting my twigs.

So do trees really fall into a deathlike slumber over winter and wake up in spring? Apparently not. While the above ground portions of deciduous trees are very much dormant, what goes on underground is quite another matter. As long as the soil temperatures remain above 32 F (0 C), roots are active.

2. My buddy is busy, too.

Trees enjoy a symbiotic relationship with a class of fungus called mycorrhizae, which also stay active, searching out water and nutrients underground, even though the air temperatures may be very frigid.

3. Feeding roots but not necessarily feeders.

The mycorrhizae bring important nutrition to the roots which are not only active, but actively are growing, replacing those that have died, and reaching out for more feeding opportunities. However, many of the so-called feeder roots that grow upward into the top six to 24 inches of earth above the main roots may be in soil that has fallen to temperatures lower than 32 F. This may have caused them to become inactive or to have even died if the temperatures drop too low in this layer of soil.

4. The sum of many parts.

One of the cool things about trees is that while they are an entity, they also have the ability to lose major parts without death. Lop off a limb – no problem. Trim off some roots, the tree rushes to grow some more. That’s why it’s a good thing that roots, like other parts of the tree, grow at different times and at different paces.

5. How do trees know when to wake up?

Our popular belief is that reduction of light hours triggers sleep and the return of light hours triggers awakening for trees in spring. However, scientists tell us that it is not day length but night length that is being monitored by the tree’s chemistry through a phytochrome, a blue pigment that, when lit by a photon of red light, is activated to turn off.

6. Wake up! Wake up! It’s warm outside.

It may be that after leaf drop there is a warm spell, but the tree doesn’t heed this. Instead it keeps on snoring above ground. This happens when the tree has been exposed to a cold spell for a certain period – dormancy has now been reached and it takes more than a warm spell to wake the tree up again.

7. The chilling hours.

In order to produce fruit, there is a period called the “chilling hours” that fruit-bearing trees (and some perennials and seeds) need to experience. This is a period that starts when the temperature reaches about 7 C (44 F) and ends around the freezing mark at 3 C (33 F). The number of hours between those two markers is what counts.

8. Apples need a long sleep, oranges not so much.

The number of chilling hours required by apple trees vary, depending on variety, between 200 and 1,500 hours, while oranges and peaches need very few hours of chilling. If the tree doesn’t get the required number of hours, it can fail to produce flowers and fruit.

9. Tree memory.

Cellular memory plays a part in the blossoming of trees in spring. This is due to a long RNA molecule called “coldair” that has recently been discovered by science. After a certain period of cold weather, the molecule “remembers”, based, scientists think, on past weather experiences. This reactivates the gene that has been deactivated in fall to repress flowering no matter what happens to the weather.

10. Don’t feed me when I’m half awake.

Just a tip: don’t smother your tree with nitrogen until it has fully leafed out. The plant can’t handle the nutrient until it is able to photosynthesize.

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