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Pruning wild plums in the understory for health and fruit production

 
Dan Boone
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Hey, I've got a question about managing wild plums (they are either Prunus Americana or Prunus Mexicana). The plums live at the back of the property (or possibly even a little bit over the line, it's somewhat ambiguous back there) as understory trees under a mix of oaks and perhaps a few pecans. The hardwoods are very old and very tall; the plums are mostly in the 15-25' range, with most fruit out of human reach. On the forest floor there's very little grass or weeds, but there is a bit of Virginia Creeper, smilax briar vines, and assorted minor shrubbery. Most of the understory appears light-starved and spindly; the plums are no exception, although they are doing better than most of the other understory trees.

It's my impression that the plums are not in good health this year; the leaves are yellowed and have spots, and some of the fruit has turned color and fallen while it is still dry, mealy, and sour. Much fully green fruit remains. We had an unprecedentedly dry April and May followed by even more unprecedented rains in June and July; August so far has been rainless as expected, and the ground has gotten quite parched.

What I want to know is how best to manage these plum trees for fruit production. The basics of how to trim branches year-over-year to keep fruiting up I think I understand, but I'm wondering whether it's possible to trim these trees down to human scale without killing them. I'm limited (because of available labor, the proximate property boundary, and the value of the hardwood trees) in how much I can open up the understory to light, but there's room for removing some overcrowded understory trees that should allow in a bit of light. But if I top these trees and tie down some of their vertical growth in a more horizontal way to stimulate fruit production, is there room to hope that the trees will survive the experiment? Or is topping likely to be too traumatic in the understory environment, where the trees already appear to be struggling?

Curious whether anybody has messed with wild plums in this sort of way, and what happened if so. Thanks!

Edited to add pictures, even though I didn't get any that really show how the trees are growing:
plum-01.jpg
[Thumbnail for plum-01.jpg]
fallen plum (not ripe despite color)
plum-03.jpg
[Thumbnail for plum-03.jpg]
plums and leaves
plum-02.jpg
[Thumbnail for plum-02.jpg]
yellow spotted leaf
 
leila hamaya
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no where near as fussy as other fruit trees, plums are super easy and hardy.

i say go for it, shape the plums anyway you want, they will respond with new vigorous growth next year.
even chopping them down to the ground will work, they come back like bushes, or just sculpturally shape them at a smaller height.
they tend to sucker and grow up from the roots, quite possibly they might share the same root and be one tree, even though it doesnt look like it.

and every branch you cut from them can become another tree, root out the cuttings. they are really easy to root, almost as good as willows in that respect.
as soon as you cut them put them in a bucket of water, either leaves them in water for a while or stick them in damp pots or ground. they do need a lot of water to form new roots, and it takes a while, but by next year you could have more plums to spread around.

or take all the branches once they are soaked in water for a time, and then dig a trench for them. put the branches in horizontally, vertically, or in half circles with both ends in the ground and given sufficient water they will reroot and form a living fence.
 
leila hamaya
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another thing you could try is layering them, especially if you do want a fence ish kind of wall of plums. you were saying you might take the branches and tie them down, if you do this all the way to the ground with the lowest branches and the tip gets in contact with wet ground, they will re root that way too. you can even half break a branch, or the whole truck, to push them over to make that contact with the ground. they can be quite bendy and do this naturally anyway...if a plum tree falls down it just re roots and then starts growing upwards from the new roots.

prunus americana is pretty distinct because of the leaf shape, i have tried to ID a lot of wild plums and its pretty tricky, but this one i can now recognize because of the leaf shape. the leaves are toothed, like a saw blade shape very sharp, and the very tip protrudes out quite a bit.

prunus americana

other similar small plums have more rounded leaves, not as long, no tip like those and the edges arent sharply toothed, more rounded.
its hard to tell from those pictures....
maybe you have prunus mexicana, or possibly something else like prunus cerasifera
 
Dan Boone
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Location: Central Oklahoma (zone 7a) ~39" rain/year
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Thank you!

I haven't made a strong effort to identify these; we've got at least five different species of wild plum in this state and supposedly uncountable hybrids between them. But mexicana is said to be the most prevalent. My local tree book has a drawing of americana that doesn't show the tip protrusion as prominently as your photos, but photos win; I'd agree that these probably aren't americana based on that but I need to take a closer look at the leaves next time I'm out there. The only thing I'm sure of is that they aren't angustifolia, because I have a bunch of those too and even when they grow like a tree they are very different.

This spring when the trees were in flower I transplanted one into my yard, and it has survived and put out some new growth, so I knew they were hardy whatever they are. The cuttings I took and set in soil didn't root, but I didn't keep them particularly wet. Wetter next time! And it's really good to know that they are able to tolerate a lot of messing with. They don't do me any good making fruit way above my head, so I think I'm going to take a stern approach to the ones at the back of the property. And I never would have thought to try a mass burying of the prunings to make a thicket. I also hadn't considered trying to air layer the branch tips, but some of the trees I've got have very long horizontal branched tops that are just out of my reach. I think the tips of some them could be trained down into the ground rather easily. So I very much appreciate those suggestions.
 
Amy Woodhouse
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Location: NC, Zone 7
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Native plums produce very well on the edges in partial shade but seem to just survive as you describe in complete shade so getting more sun is the most important thing. You can run over plums with a bush hog and they will throw up suckers and come right back so they are pretty tough. We have a fairly large plum tree in our woods that was knocked over by a larger tree that fell on it. The plum tree rooted where it was touching the ground. I would wait until they are dormant just to reduce stress and cut them at the base. Next year when the suckers come up you can pile dirt around them and the following winter you dig up the rooted suckers. You can also just cut them or bend them over and root them as Leila stated...rooting the cuttings just takes a little care so they don't dry out. Good Luck!
 
Dan Boone
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There's a bunch of suggestions on the web to do major pruning on prunus species in midsummer to avoid some sort of leaf disease. But that's simply not an option for me, it's too hot out there for extensive labor. And I figure winter dormancy is a better time anyway if I'm going to be topping or otherwise really massively altering the trees.

This thread is giving me a lot of reassurance about going interventionist on these trees. And there are a lot of them (20+) so I can afford a few mistakes. But getting more light down onto the forest floor is going to be the hardest part, since I'm not willing (or able, really) to cut the healthy canopy trees. I do think there's quite a few senescent canopy trees that ought to come down; there are already plenty of dead snags for wildlife. I'll have to get out there in the winter, clear out some of the understory junk, and then look at the big trees with a cold eye when they start leafing out in the spring.

I've already got a use for the poles and sticks I'll develop when clearing out the understory. There's a nascent ravine forming through this forest, that goes from a six inch ditch where it first becomes visible to a full-on ravine eight feet wide and six feet deep where it meets the creek. I've been thinking of building some wooden sediment weirs across it at the upper shallower end to slow its progression. The soil is fairly soft so I think I could hammer in a line of small sharp-ended poles without a ton of effort.

 
leila hamaya
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hey, you're welcome.
i am really into plums (and cherries -other prunus species) lately for a lot of reasons. right now i have been preparing and cleaning a bunch of seeds, some hundreds of seeds of different plums and cherries. i like that they can be feral trees, and thrive regardless of human care. i really like that they can grow close together and be hedge rows, a good base for living fences, and are just so easy to grow and have that rerooting ability.

and i am really fascinated, almost obsessed, with the idea of making living walls and fences. i have seen some cool ones that people made, one that my friends made which is a garden fence with a lovely plum with dark leaves, by putting the long cuttings in half circle shapes and both ends in the ground. it came out really great, and works well.

i have some small projects i have been slowly working on making living fences with plums, perhaps in a few years i will have some pics to show, it is sooooo slow, but very cool. last winter at my friends house i started one using the trimmings from their plum trees, it took and just started really growing, its still pretty tiny. in a couple of years it should be very cool. i started another one from seed, but then i moved...its definitely a project that takes staying in the same place for a long time.

some people even sculpt them, i have seen furniture and cool arborsculpture done with plums and cherries.

i also take a lot of cuttings of trees and vines, and have had my share of failures to re root stuff. figs and plums are some of the only ones i get to work out well, and for me the key has been to soak them for a long time, and then place them horizontally in trenches and keep them watered.
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