Monday, March 01, 2010

Technique Tips: Pruning Weeping Mulberry

Oh, what a tangled web we weave... when we don't know how to prune a weeping mulberry (Morus alba 'Pendula'). You can see this popular weeping standard tree all over the city – and when not wearing its cloak of green, the tangled, haystack-headed results of improper pruning are only too evident.

Therefore, when I do happen upon a weeping mulberry that's even close to looking the way it's meant to look, I put on the brakes and hop out with the camera. Voici:

When I point out the good from the bad, I've had people say to me in disbelief: That's the same kind of tree? Why, yes, by gum, it is – only with some attention to pruning. With spring on its inevitable way in, the next week might be one of your last chances to prune, as it's best done during dormancy. Otherwise, cut branches have a tendency to bleed.

Naturally, when pruning any trees or shrubs, the first rule is to cut out any dead and/or crossing branches. The same thing applies with the weeping mulberry. But there are also more specific techniques, and they're easy, once you know how. The weeping Camperdown elm (Ulmus glabra 'Camperdownii') should be pruned in a similar fashion.

The tree above isn't perfect, by any means. At some time in its past, the caretaker allowed one of the vertical branches to remain, and if this keeps up the tree can become too tall and difficult to reach for pruning. You can see the runaway vertical branch rising from the centre of this tree form. 

So that's the second rule for pruning the weeping mulberry: cut off any vertical or upward-growing branches.

However, let's talk about what they've done right here. Do you see the open form of the tree, compared to the first example, with its branches cascading in a waterfall pattern? Here's a closer look.

The lower branch shows what correct pruning can produce over many seasons. See how the branch seems to make a series of little bridges?

Below is a shot of what typical branches would have looked like before the cuts. I'll give you a nice big image to make the tangle clearer.

Can you see the type of branch forms where you would make a cut to produce those little bridges? In this case, I've circled possible cuts on the same branch – you'd make one or the other. Cut close to the joint, without leaving a stump.

Can these trees be saved? Perhaps – over time. The job is complicated by the volume of untrimmed branches from past seasons. When pruning, it's rarely a good idea to cut out more than one-third of the branches at a time (some shrubs are exceptions, but I won't go into them here).

A weeping mulberry is in fact a prostrate or ground-hugging shrub that has been grafted onto an upward-growing trunk. If you cut back your weeping growth too far, you risking having the species in the standard or trunk take over.

The best scenario is to start building the form of the tree while it's young. And if you have a young or young-ish weeping mulberry, you have a chance. So... read this and weep.

[UPDATE: Since posting this, a few people have written to us to ask for advice on pruning their own weeping mulberry. We should note that the art of pruning is something that can't be done remotely from photos. Also, it can be difficult to rehabilitate a mature tree of any kind if it hasn't been well-trained from an early age. If you have a mature tree that needs serious attention, and you don't want to attempt it yourself (which you should never attempt if there's the chance of injury to you or your tree), our best advice is to contact a local certified arborist for consultation and/or service. Tree people do it best.]

26 comments:

  1. I adore weeping mulberries! They are so incredible.. but I'm always afraid to prune them too much. Thanks for the great post!

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  2. What a difference between the two. I feel sorry for the one in need of a good trim, it really looks shaggy. I had no idea the standard could take over - what good information!

    Cheers!

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  3. Helen girl .. I can't tell you how many of these trees exist in Kingston .. there must have been a HUGE sale at one time ?
    And ..the ones that aren't pruned properly ? OMG .. even ones that are growing into the ground .. they make me shudder .. I bet you would too ? LOL
    Joy

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  4. Hi Helen - what a great post. Wish it could be sent out to everyone who has an "umbrella" growing in their garden.

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  5. Great advice Helen. I've never seen a Mulberry tree, guess they are not hardy where I live.

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  6. What a difference proper pruning makes! I think the weeping mulberry is a beautiful tree, as seen in the second photo. Excellent post!

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  7. Great post, hopefully a lot of mulberry owners will read it and weep.(and then prune properly).

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  8. Great tips for pruning! Just found your site and I'll be back to look for more great info. Thank you.

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  9. I would never have guessed that both trees were the same. What dramatic structure the second tree has. I guess people just don't know what to do and so trim the branches as if to give the tree a haircut. You've provided great instructions on pruning here. I'd love to see a pic of the second weeping mulberry when in leaf.

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  10. Hi Helen,
    I was talking to an arborist about my neighbours Weeping Mulberry and said "The Parks Department seem to a good job pruning them" and he said " it's the only thing they know how to prune".

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  11. great post! Thanks for the reminder about getting out there and pruning before it gets too late!

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  12. Wondering if it should be pruned before winter or before spring???

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  13. Anonymous -- mulberry is technically a fruit tree (although the weeping form is often sterile and makes no fruit), so can be pruned as such in late fall (close to frost date) or in early spring before the leaf buds begin to open.

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  14. We have a large weeping mulberry out front of our home, and I am wondering if we cut it right back, can it regrow? The tree is about 15' high, was not cut at all by the past owners, and most of the tangled branches do not even grow leaves. In order to cut it back to size, we would be removing all of the smaller branches, and leavning only the tree stump and a few 12" diameter upward growing branches.

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    1. Be careful how drastically you cut back your mulberry, as the weeping portion has been grafted onto an upright-growing root stock. The demerits outweigh the benefits of a mulberry that isn't in weeping form. I'd really suggest going to an arborist for advice. The cost of an arborist's attention can really be worth it if you want to retain a mature tree -- and nothing quite replaces a mature tree in the landscape. Check the International Society of Arboriculture website to find a certified arborist near you.

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  15. My weeping mulberry is about 15 yrs old and is thick with healthy green leaves every summer. Is it OK to trim it when the leaves have grown right down to the ground, otherwise it just looks like a big green mound on my lawn. I have been giving it a trim a when it get to this point every summer and again in the fall.

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    1. Trimming your weeping mulberry in early spring before the leaves disguise the branching system is pretty much a must if you have this tree. Shorten the branches, as you suggest, and also lighten up the internal bone structure as I've suggested above so that it looks a little like Cousin It (see: Addams Family) during the summer.

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  16. We cut down a mulberry tree in front of our home this spring, I didn't know how to trim it, and it was a mess, a lot of the branches were dead. Now, however, it's growing up from the stump, it even pushed up my landscape cloth, and I had to cut a slit and let it out. Will it grow to any attractive form at all in its natural state not grafted? Any info would be greatly appreciated!

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    1. The Tree can revert to its original form (not weeping) if trimming to aggressively, light trimming every year is preferred as compared to on drastic cut back. When you are posed with a tangled web of an unkept weeping mulberry, trim some early spring and let it rebound and do it again late fall to take the rest off (if possible). This method puts less shock on the plant, but does require pruning at least two times. So the plant is taking more stress over a longer period of time as compared to all at once.

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    2. The suckers that sprout from the stump will be whatever species was used for the trunk below the graft. Typically, this will be some upright form of mulberry. However, it won't be a dwarf tree, like the weeping form was -- it can grow quite large, and will be multi-stemmed. Unless you have a large garden and/or value the mulberry fruit, there are many other more attractive landscape trees than the common mulberry. Personally, I'd rip off the suckers, dig out the tree root and start again with something else.

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  17. I purchased a Weeping Mulberry a few years back. In the past couple years the new growth has been growing straight up and not in weeping form. Is this perhaps the root stock taking over at the top? This new growth is coming from the graft at the top so I don't understand how that could happen. Any advise? Thanks. Steve.

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    1. Steve, It's fairly common for the trunk species to sprout upward at the point of the graft. When this happens, prune that straight branch back right away, and as close to its point of origin as possible. Don't leave a stump. The trunk species is much bigger/more vigorous than the weeping mulberry species and can soon overpower your tree.

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  18. "At some time in its past, the caretaker allowed one of the vertical branches to remain, and if this keeps up the tree can become too tall and difficult to reach for pruning. You can see the runaway vertical branch rising from the centre of this tree form. "
    I have to disagree, the branch that rises in centre is not a sucker from the trunk, but a series of weeping branches from above the graft. This gives this tree a much needed vertical dimension but is in no way a threat of becoming too tall/large (as it is the weeping form). If it was a 'vertical branch' from the trunk (as is often seen, it's true) it would never revert to the weeping from seen on the top of this branch.

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    1. Hi, there, I didn't mean to suggest it was a sucker (it clearly isn't). However, you'll have to admit that if the vertical dimension becomes too vertical, too often, it can make for a difficult-to-manage tree.

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  19. I guess the word "runaway" mislead me. It's difficult to judge, but in the photo it looks like it took at least 10 years for the branch to grow; more of an amble-away. If gaining four or so feet in a decade makes for difficult to manage trees...

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    1. I understand your point. But any tree pruning that requires a ladder and over-reaching eventually does become hard to manage, which is what I was trying to say.

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