Neighbor Stumped by Mysterious Trunk of Sidewalk Tree


Over the break, Neighbor Matthew wondered about the odd tree in front his house on Wool Street:

What’s the deal with the strange Bernal trees that are stumpy on the bottom and narrower on top? See attached photos. I have noticed these while running all over the ‘Wood Hood. This photo is from in front of my house on Wool Street. I’m stumped (wakka wakka wakka) as to whether these trees grow this way naturally, whether they had some sort of disease, or whether a smaller tree was somehow transplanted into a previously larger tree.

Any insight from Bernal’s many armchair arborists?

PHOTO: Neighbor Matthew

28 thoughts on “Neighbor Stumped by Mysterious Trunk of Sidewalk Tree

  1. My guess is that its likely due to grafting the tree on to rootstock?

  2. Your tree is grafted. Grafting is a horticultural technique whereby tissues from one plant are inserted into those of another so that the two sets of vascular tissues may join together. This is great because the root of the tree is established and the new graft can grow fast.
    Some gardeners have one tree with different fruits on it from the same family. You can have peaches, apricots and plums all grow on the same tree.

  3. That only partially answers the mystery. I think the bigger question is: why are there so many of these around the neighborhood? Was there a storm, or a disease that caused them to cut down a bunch of trees at once?

    • I suggest contacting FUF (Friends of the Urban Forest, for an explanation. I did not see any mention of grafting on their site, but they do have resources describing the species they recommend and even a map showing what has been planted thru their auspices.

      But my guess is that grafting is done for the reasons grafting is always done. To get a best fit for the intended uses. You combine hardy root stock – that can survive harsh urban conditions, or possibly less eruptive root growth that has a lower risk of damaging sidewalks – with a canopy that won’t get too tall, or obstruct the sidewalk, etc.

      The thick stump compared to the canopy suggest a hardy, strong root stock combined with a dwarf tree canopy. Would make sense to me, but it would be best to hear from FUF.

    • This is how they come from the nursery, not something that has happened in situ. You’ll note that almost all (if not all) the grafted trees we see in Bernal are heavily flowering ornamental cherries. This kind of cherry isn’t the longest-lived tree outside its native range, so you get them grafted onto a heavier rootstock that grows much, much sturdier than the ornamental tree that’s spliced onto it. The result, over time, is a base trunk that’s thicker than the crown’s trunk.

      Nurseries each have their own preferred type of grafting. I notice that a lot of the cherries on the south side of the hill are all grafted just below the crown, so most of the trunk you see at street level is the rootstock (above which the trunk narrows quickly and branches emerge). This one looks older, and probably came from a nursery that preferred to graft much lower than what’s popular now.

      • Hm. I concede all the practical reasons, but take issue with this one. I think it’s a very unfortunate looking tree, which I think makes it very far from perfect. But beauty is in the eye of the beholder.

  4. It’s the graft line where the ornamental pear was grafted on to sturdier or, more likely, dwarf rootstock.

  5. We have a tree on second block of Eugenia like that. When it was planted, the strap to hold it was left on too long and that is where the size changed. Later the strap was taken off but the deformity remained.

  6. Trees can’t get too big in our mini-hood (7/8 scale to Noe I figure). So the trees might have been topped or chopped years ago.

    • They may have been pollarded. Like the trees in Civic Center Plaza across from City Hall, and all over the city. See my comment below.

  7. This is so interesting. I’ve always wondered why my cherry tree in the back yard looked like this (fat on the bottom and skinny branches up top) and why my magnolia has both pink and white flowers. Apparently grafting explains it all.

  8. It’s grafted. This is universally true of apple trees, for instance. The exotic apple varieties cannot grow well on their own, so they must be grafted onto a more hardy variety of apple tree in order to survive.

    • What I learned from Michael Pollan’s book, The Botany of Desire, is that each apple seed is unique and bears no resemblance to the other seeds in the same apple or the parents. Apple trees are grafted in order to get the fruit you want.

      Grapes are grafted to native grape rootstock because of diseases.

      Everyone, go out and read this book! Fascinating and fun (as is his book about gardening, Second Nature)!

      • A nitpick. Each apple seed is unique. A discrete individual. But they DO resemble each other very much. They can even be genetically identical. I wonder why Pollan even mentioned it.

        Does it matter? I dunno. It’s true though.

        (Why do I care? We have so many fascinating science writers in the Bay Area who strive for accuracy. Read anything by Mary Roach. Pollan isn’t a science writer. Maybe philosophy? Advice?)

  9. There is no reason to believe the trees are “replacement” trees. They are just grafted trees, planted as grafted trees. If a tree dies or is diseased, there isn’t much point in grafting a “new” tree onto a dead or dying stump.

  10. I see a lot of trees cut off, and new branches grow from the stump. Is it not this? I’ve definitely seen it, just maybe not this one.

  11. This appears to be a flowering cherry tree that has been grafted onto the tough rootstock of another cherry species. Most grafts are done at the base, but this one appears to be at 3’. Nurseries do this for various reasons, such as to create trees with tough roots and delicate flowers. But indeed it can result in a strange appearance, as is the case here.

  12. Some of you are describing pollarding. At the desired level, all the main branches are cut back close to the trunk. The tree resprouts many more branches in response. A higher number of smaller branches at the top of a large trunk starts to resemble the kid-drawn version of a tree that some prefer. A green lollipop with a brown handle. It is a way to reshape a tree species that doesn’t naturally have that form.

    In case that bugs anyone: it is a natural characteristic of trees, and plants in general. Example: Black Acacia trees, in a forest of Acacias, are straight and branchless for 70 to 80 feet. In your backyard, a solitary acacia will be short, many branched, twisted and gnarled.

    The original picture shows an example of grafting. The most common California example is Walnut farming. North American walnuts are bitterer than English varieties. So English walnut bodies are grafted onto California rootstock. The area around the site of the graft provides incredibly beautiful (and expensive) wood called “paradox” or claro walnut.

    Someone already explained coppicing, of which I don’t know any Bernal examples…

    That tree in the picture isn’t super awesome looking. But it gets Charlie Brown Christmas Tree love from me. It’s also got the underdog trump card: if it ever dies, that ugly graft will make for gorgeous wood. There is the potential for it to have a second life as something useful and beautiful.

    It looks like an upright snail with antlers.

    • The black acacia grove along SJ avenue shows this but, what I can tell it is the younger trees (or branches since the tree is weed like, growing all ways) are the ones that are bushy but probably because they have to get up to the canopy for light. This is just observation. Those things seed a fern like plant which quickly becomes a busy tree which we don’t allow beyond this stage because big trees – big roots.

  13. There are many trees that look like this cause they were all grafted. It’s not for “perfection” for selected traits that the breeder thought made a desirable tree…
    I’m a retired gardener, if there is such a thing…

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