Quiz time!

One of the things we Garden Professors can do is give tests!  And the nice thing is you don’t get penalized for being wrong.  So this will be my inaugural Plant Puzzler.

Below is a photo of a tree with epicormic shoots on its two lower branches.  Epicormic shoots are vigorous, upright branches that have more of a juvenile than mature appearance.  They often appear when a plant has been stressed, perhaps by overpruning, or maybe the roots were damaged by construction:

So here is your test question.  Why are these epicormic shoots primarily (if not exclusively) on the two lower branches, and not elsewhere in the crown?  (You can’t see the top of the tree, but I promise there are no epicormic shoots up there.)  And what evidence would confirm your diagnosis?  While there is only one correct answer for this particular tree, let’s see how many possibilities you can come up with.

Answers and more pictures next week!

 

10 thoughts on “Quiz time!

  1. Being from down under, epicormic shoots are something we horticulturists know quite a bit about. The genus Eucalyptus abounds with species who produce epicormics readily. In Eucs they're usually triggered by fire or limb shedding, or some other form of stress.

    Not being familiar with northern hemisphere species' propensity to produce epicormics, I can't be sure. However, I notice a notch on the the right hand lower branch, about half way up. Could it be rot or a wound an animal might have made in the limb that prompted the epicormics to grow?

    As for the epicormics being localised to the two lower branches, the only thing I can come up with is that the lower branches are closer to the ground and therefore more likely to be damaged in some way by ground-dwellers (human or otherwise). Perhaps deer grazing?

    What fun! I love a good quiz!

  2. Erm .. as a balcony gardener I'm not too good on trees, but I'll have a go. They remind me of something out of Harry Potter or lord of the Rings so … wizard damage possibly??

    OK, OK, grade E and a detention for facetiousness – but I will come back to find out the answer, and hope you'll do lots more tests.

    Found you through Blotanical incidentally …

  3. sorry, I have no idea. just wanted to let you know how much i enjoy the blog and am looking forward to learning the correct answer.

  4. I like the first answer, though I'd modify it to suggest that trucks perhaps nicked the lower branches — it looks from the photo as if the tree is in/next to a parking lot. Or maybe the tree's owner whacked back the ends of the branches to prevent truck damage (!), and so triggered that epicormic growth?
    Good quiz!

  5. Is the rest of the tree, outside of the branch with the epicormic shoots, alive? If not, are these shoots the tree's last ditch effort at life?

  6. On the other hand it could also be a matter of physics… epicormic buds, such as those found in our Eucalyptus, are notorious for falling down when they get some size and weight about them. If you look at a cross section of the branch junction from where an epicormic bud has grown and matured you can see why this is so. The only solid wood that is continuous with the wood in the parent branch occurs across the top of the 'join' at the epicormic bud's origin. The bottom part of the epicormic branch is cantilevered against the trunk with a thin layer of bark around it. Growing upright, as they often do, reduces the effect of gravity on the limb by putting the centre of gravity more directly within its footprint and within the load limit of this weaker join. Maybe the top or centre of the tree has been damaged in some way (the image is a bit small to see properly)and the tree has 'determined' the best place to grow new branches was where the next best strong almost horizontal branches were to serve as a solid foundation and allow vertical growth. It is also well known that pegging rose branches into a horizontal position initiates the growth of all the dorsal axial buds along its length and they all grow vertically. This is how we force climbers, or roses with long limber canes, to develop more flowers because all of those axial buds will terminate in flower.. otherwise we get a small number flowers right at the end. So plants can not only tell what angle their branches are growing at but also which way is up (a negatove geotropic response). Maybe this is a tropic response, iniated by auxins, in response to some damage and the orientation of the the lower branches relative to gravity was determined to be the next best place to activate those dormant epicormic buds.

  7. WOAH! I just realised that the image above, though small on the page (and non-clickable) is huge in reality! If you are using IE click on the image, hold it, and drag it onto the next page tab (or copy it's url into the address bar of a new window) at the top… you'll see the image by itself full size…. I can't see any obvious damage to it up close.

  8. I think Deb nailed it. Both lower branches look pruned to allow for parking. From the size of the wound, one of the braches was fairly large. Good quiz and blog!

  9. Thanks, PCP and all the rest of you with your kind comments and brainstorming! I'll be sure to continue the Friday quiz.

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