Callery Cedar

 

Note:   This is an update to a blog story started in 2018 with a chance find of a callery pear tree growing out of a eastern red cedar.

 

2018:  

Barb called me a few weeks ago to tell me that she had found a Callery pear tree (think Bradford) next door that was growing out of the trunk of an eastern red cedar.  I won't go on to say what I thought at the time as she edits this blog.  As I trust her fully I only said, "Oh?"

 

Pear above junction with the parent cedar.

When I got home I went out to see it for myself.  Indeed, there is a Callery pear tree, Pyrus calleryana, 2.5" in diameter emerging from the cedar's trunk three feet above the ground!  It is healthy and happy, approximately 12' tall and in full bloom.  The cedar appears healthy and is the same height as its mates along the line.

Cedar limb scar with Callery pear exiting above - Click to enlarge

Base of pear - Click to enlarge

Close up you can see that a branch was sawed off years ago.  The Callery emerges from the top edge of the scar, which is 3" in diameter, on a 9" DBH (diameter at breast height) cedar.  There is no visible opening to suggest a cavity where a seed might have fallen in the past. 

The first thought might be that it was grafted.  Bradford pears like all other flowering broad-leaf trees are angiosperms and can't be grafted onto gymnosperms such as junipers and pines.  (Technically, our "eastern red cedars" are not cedars, they are junipers, Juniperus virginica.)

The current consensus** of several forestry people is that some time in the past fifteen or so years a bird passed a seed onto the branch and it landed in a crack in it.  Perhaps the bird's feces provided it a little nutrition and a break in the cedar bark allowed some water to collect.  A big question remains - does its roots extend to the ground or is it getting its nutrition from the cedar itself?  I hope to protect it until someone can study its vascular connection to either the cedar or roots extending into the ground.  Regardless of the details it certainly was a one in a million occurrence.

Callery pear trees were brought to the US in 1916 from China to combat fire blight in the common fruit pear (Pyrus communis).  Once they were found to be relatively resistant, 100 pounds of seeds were imported to develop a resistant genotype.  Over the years more seeds from across China, Japan and Korea were collected and made available to nurseries.

In 1952, the ornamental possibilities of one particular vigorous, thornless tree were recognized, and cuttings of it were grafted onto P. calleryana seedlings.  After 8 years of successful testing in nearby neighborhoods they were named "Bradford."  They are unable to self-pollinate, therefore the trees, by themselves, couldn't set fruit. Their vigor was described by USDA plant explorer Frank Meyer in 1918 who had first collected the seeds.

"Pyrus calleryana is simply a marvel. One finds it growing under all sorts of conditions; one time on dry, sterile mountain slopes; then again with its roots in standing water at the edge of a pond; sometimes in open pine forest, then again among scrub on blue-stone ledges in the burning sun; sometimes in low bamboo-jungle...and then again along the course of a fast flowing mountain stream or on the occasionally burned-over slope of a pebbly hill."

When a species is described as thriving in any condition, tolerating all enemies, and like Superman "able to leap over tall buildings in a single bound" you are describing an invasive species.  Soon there were several cultivars produced across the country and when they were planted together as my dad would have said, "up jumped the devil."

A cultivar with striking leaf color in Oregon became Autumn Blaze. Aristocrat, from seedlings growing at a nursery near Independence, Kentucky, had a strong central leader with horizontal branches and an early pyramidal form, more sturdy that the somewhat fragile Bradford.  Chanticleer, cloned from a street tree in Cleveland, Ohio, was named the 2005 Urban Tree of the Year by the Society of Municipal Arborists.

"Callery in a Cedar Tree" -  Click to enlarge

This was all well and good as they weren't self-pollinating but soon innocent insect species began moving pollen between different cultivars planted a few hundred feet apart. Their offspring began creating their own hybrids that could reproduce.  It was as though the individual varieties that had occurred natively in China had all moved into the same neighborhood and had a giant angiosperm orgy.

3 new branches 2020 - Click to enlarge

 

 

 

 

I would nominate Callery pears as our most invasive plant species, pending the discovery of garlic mustard growing on the back of a zebra mussel.  I am proposing naming this Callery/cedar tree shown above, Juniperus calleryana var. Barbarae, in honor of the discoverer.
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Update 2020

Now two years later there are three branches growing out the other side of the trunk as well.  The cedar is otherwise healthy looking.

New Callery growth 12" from the cedar base

Update September 2021  

New growth -Click to enlarge

Continued growth of all the original branches (red arrow) with two new small branches growing out  of the bottom two feet of trunk on the other side.  Also, a new growth with leaves coming out of the soil one foot from the base of the tree (lower right arrow).  While that could be a separate seedling there aren't any others in the surrounding area.  This would seem to settle the question of nutrition as the Callery now has roots in the ground through the cedar trunk!

There are now 26 cultivars of Callery pears. Twelve of these are currently being sold. The Missouri Invasive Plant Council will be making an effort to cease the sale.

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Update-- April 10, 2023

This report is from a site visit by Dr. James Guldin.*

"That Callery pear growing from a knothole in the eastern red cedar is a fine demonstration of adaptive physiology on the part of the pear. It takes some imagination to describe how the pear can coexist with the red cedar.  It also takes some thought to account for how the pear tree gets enough nutrients and water to develop into a 3” diameter stem growing out of that knothole in the red cedar that is 4 ft above the ground.

The availability of nutrients is the easier question. When rain flows down the stem of a tree, the water in the stem flow is enriched by nitrogen, phosphorus, potassium, and the micro-nutrients that a tree needs to survive, no doubt by leaching those nutrients from the bark. That flow of nutrient-enriched rainwater down the stem of the red cedar finds its way into the holes, nooks, and crannies into the dark interior of the host tree. The roots of the pear got their start in those nooks and crannies, and by now have developed to utilize the macro- and micro-nutrients that the pear needs to grow.

But to me, the availability of water is the larger question. How do the twigs of a Callery pear stem look vigorous today, and flowering today, without any apparent contact with the ground to provide the water that the above ground stem needs to grow and thrive? There are two possible answers.

One, the roots of the Callery pear are also 3-4 feet above the ground, embedded in the decayed core of the red cedar, and the stem flow of water into the nooks and crannies into the punky decayed core of the red-cedar may provide all the water the pear stem requires. In the spring, I can buy into that hypothesis. But in the summer, even the decayed wood in the red cedar will become dry as dust, and I doubt the stem of the pear could drink up the water it needs on a daily basis from dry punky rotten wood. The stem would have died before we saw it today.

Two, more likely I think, is this—the roots of the Callery pear have wiggled, writhed, slithered, and otherwise grown downward through the decayed center of the decayed stem of the red cedar into the soil, below the root collar of the red cedar. If this is the case, the pear would be able to suck up the water it needs from the soil below and around its red cedar nurse tree. It might even continue to grow and thrive into, well, maybe a 3” diameter stem that’s flowering and showing twig elongation—as this stem is doing.

If this tree is ever cut for some residential purpose, a close look at the stem analysis would show whether the roots of the pear have made grown into the soil at the bottom of the stem of the red cedar." 

Dr. James Guldin is a recently retired forest scientist (University of Arkansas and US Forest service).  He serves on the board of the L-A-D Foundation.
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Callery pears and their 'Bradford' kin are now spreading wild and are considered possibly the greatest invasive plant species threat in Missouri.  In the words of Nathan Muenks* of MDC:

"It’s difficult to truly determine which invasive species is most impactful, but Callery pear sure ranks up there with bush honeysuckle, sericea lespedeza, spotted knapweed, feral hogs and a few others. The reason being that it I would consider it an “ecosystem changer.” Given its ability to invade many of Missouri’s habitat types (whether open or wooded) and the fact that it forms such dense thickets, it has the ability to drastically out-compete native flora and drive away native fauna by creating unusable space for them. It not only grows dense, it also grows quickly. In addition, it’s a tree, vs. bush honeysuckle and others, so it can tower into the upper mid-story – what hope do our native, slower growing trees have in competing for resources and regenerating our native forests and woodlands?

There is no doubt bush honeysuckle and other invasives are much more widely distributed and affecting more natural communities at this time, but there is a strong fear that Callery pear is on a very similar trajectory. While in St. Louis yesterday, I noticed that bush honeysuckle and Callery pear tended to do just fine growing together, with honeysuckle dominating the low under-story and the Callery pear towering above it – SCARY! Is this the future of Missouri’s landscape? It could very well be if we don’t halt the invasion and join in this fight together!"

*Nathan Muenks is the Habitat Management Coordinator with the Missouri Department of Conservation.  This includes coordinating the Department’s terrestrial invasive species management efforts.