What is causing the leaves on my Thundercloud plum trees to drop? - Ask Extension
I have two thundercloud plums that are about 10 years old. The last several years they have started dropping leaves and small twigs shortly after the ...
Knowledgebase
What is causing the leaves on my Thundercloud plum trees to drop? #237935
Asked April 18, 2015, 5:25 PM EDT
I have two thundercloud plums that are about 10 years old. The last several years they have started dropping leaves and small twigs shortly after the blossoms have fallen. It is only April and the leaves are already falling. Any idea what the problem is?
Clackamas County Oregon
Expert Response
Tell us a little more. Are the leaves discolored, misshapen, or otherwise damaged before they fall? What percentage of the leaves fall? Do you subsequently get nice-looking replacement foliage--i.e., later in the season does the tree look fully recovered? Are only the newest leaves affected, those at the ends of the twigs, or is the damage mainly the oldest leaves, or are both new and old leaves affected equally? Have you happened to notice whether other plum trees in the neighborhood show the same symptoms?
Does all of the fruit drop, or just some? How big is the fruit that drops? I what drops smaller than fruit that doesn't drop? On previous years when this happened, did you get a good crop from the fruit that remained on the tree? On years when you did not have this problem, how much fruit did you get?
Also--the last two years we have had cold weather after the first warm days of spring--did you happen to notice the night temperatures for the week or so before this leaf drop?
BTW, Thundercloud Plum is grown for its foliage (and shade); in the Pacific Northwest it almost never fruits--which makes me wonder if this is perhaps a different variety.... Do you remember where you got it, and / or why you assumed it was the variety Thundercloud?
Is it possible for you to send a couple of close up photos--one of damaged leaves, preferably while still attached to the tree, and one of undamaged leaves of about the same age?
Thanks. Look forward to hearing from you. (Please reply directly to this message, so your response doesn't go to a completely different person, who won't have access to your original information.)
Does all of the fruit drop, or just some? How big is the fruit that drops? I what drops smaller than fruit that doesn't drop? On previous years when this happened, did you get a good crop from the fruit that remained on the tree? On years when you did not have this problem, how much fruit did you get?
Also--the last two years we have had cold weather after the first warm days of spring--did you happen to notice the night temperatures for the week or so before this leaf drop?
BTW, Thundercloud Plum is grown for its foliage (and shade); in the Pacific Northwest it almost never fruits--which makes me wonder if this is perhaps a different variety.... Do you remember where you got it, and / or why you assumed it was the variety Thundercloud?
Is it possible for you to send a couple of close up photos--one of damaged leaves, preferably while still attached to the tree, and one of undamaged leaves of about the same age?
Thanks. Look forward to hearing from you. (Please reply directly to this message, so your response doesn't go to a completely different person, who won't have access to your original information.)
Justin,
I am enclosing some additional pictures of my thundercloud plum as you requested. As you can see from both these photos and the ones I included originally, the tree leafs out nicely in the spring. Shortly thereafter, though, the leaves start dropping throughout the tree so that it actually is a thinning process over a period of time. Fruit dropping is not an issue since the tree is an ornamental although there is an occasional dime-sized piece of fruit produced. You will notice that there are small holes in the leaves and almost all of the leaves on the tree have them. Along with the leaf drop there is also an occasional small twig dropped that has two or three leaves still attached,
Thanks for your help.
Rob
I am enclosing some additional pictures of my thundercloud plum as you requested. As you can see from both these photos and the ones I included originally, the tree leafs out nicely in the spring. Shortly thereafter, though, the leaves start dropping throughout the tree so that it actually is a thinning process over a period of time. Fruit dropping is not an issue since the tree is an ornamental although there is an occasional dime-sized piece of fruit produced. You will notice that there are small holes in the leaves and almost all of the leaves on the tree have them. Along with the leaf drop there is also an occasional small twig dropped that has two or three leaves still attached,
Thanks for your help.
Rob
Ornamental plum trees can show damage from even light hail or late spring cold.
Thanks for the additional photos. What I am seeing is very healthy spring growth --with leaves showing holes, some tears, and a scattering of tiny light-colored dots. This is very consistent with small hail damage, and we did get those conditions at the appropriate times to show these results. When the leaves first come out and are initially growing, they are quite thin and quite tender--even small hail can cause these holes and tears. More surprising, to me, was to discover that even the few instants that the ice is on the leaves is enough to cause tiny, localized freezing --the light colored dots.
Your photos show no signs of biological agents; either disease or pests.
New growth should be trouble free (barring additional late storms!). (Existing damage will continue to exist--plants do not "heal" the way people and animals do.) If you see areas of discoloration developing in the future, or if you see larger or more irregular holes later in the season, please send new photos and re-ask the question. But for now--what you are seeing seems exactly like what one would expect with the weather we have been having!
Thanks for the additional photos. What I am seeing is very healthy spring growth --with leaves showing holes, some tears, and a scattering of tiny light-colored dots. This is very consistent with small hail damage, and we did get those conditions at the appropriate times to show these results. When the leaves first come out and are initially growing, they are quite thin and quite tender--even small hail can cause these holes and tears. More surprising, to me, was to discover that even the few instants that the ice is on the leaves is enough to cause tiny, localized freezing --the light colored dots.
Your photos show no signs of biological agents; either disease or pests.
New growth should be trouble free (barring additional late storms!). (Existing damage will continue to exist--plants do not "heal" the way people and animals do.) If you see areas of discoloration developing in the future, or if you see larger or more irregular holes later in the season, please send new photos and re-ask the question. But for now--what you are seeing seems exactly like what one would expect with the weather we have been having!
Justin,
Normally I would agree with your assessment. However, this is the third year that this has happened and my major concern is not the holes in the leaves but the leaf dropping. As spring progresses, the foliage on the tree simply thins out as the leaves fall on the lawn. I have previously sprayed Bayer Advanced 3 in 1 Insect, Mite and Disease Control on the trees and that seems to have helped the leaf dropping. However, when it started dropping again this year, I was hoping for a definitive diagnosis of the cause.
Rob
Normally I would agree with your assessment. However, this is the third year that this has happened and my major concern is not the holes in the leaves but the leaf dropping. As spring progresses, the foliage on the tree simply thins out as the leaves fall on the lawn. I have previously sprayed Bayer Advanced 3 in 1 Insect, Mite and Disease Control on the trees and that seems to have helped the leaf dropping. However, when it started dropping again this year, I was hoping for a definitive diagnosis of the cause.
Rob
Rob
You have set an interesting question.
There are many fungal, and a few bacterial diseases that are collectively called leaf spot diseases. Your trees have none of them (at least to any significant degree) because all cause deformation, discoloration, or progressive spot growth of the leaves. Your photos show healthy young leaves with some physical damage. Given that we've had light hail several times, and it causes symptoms exactly like your photos, and I've seen similar damage on other trees within a few miles of you, I'm pretty sure that is the cause of the leaf damage. Last year we had similar conditions; this is not uncommon.
That still leaves the question of the foliage drop.
Virtual all of the biological agents that cause leaf drop, as noted above, cause leaf deformation, discoloration, or progressive spot growth--your don't. Hmmm. In fact, one little known but critical fact in our work is that upwards of 95% of all residential garden problems are caused by abiotic factors: not bug or diseases, but either climate, poor plant selection, or "things people do"--like bad planting, over or under watering, over fertilizing, inappropriate weedkillers, etc. etc. Your photos show mature plants (so, not obviously poor planting), that don't show obviously bad pruning, in an apparently healthy lawn situation, with no obvious recent ground disturbance and no obvious pesticide (weedkiller) damage..... The most common villains do not seem to be actors here.
The critical question is: does healthy new growth completely replace the fallen foliage? If yes, whatever caused/causes the problem is transitory, and not serious (most trees can actually defoliate completely between 3 and 5 times in a year without causing permanent damage; that is obviously not what is happening here).
If, however, the die-back is permanent, with resultant bare branches or lots of bare twigs that do not re-grow new leaves, then the problem is more serious than freaek or unusual weather. Plums here can be susceptible to Armillaria root rot (http://www.ipm.ucdavis.edu/PMG/GARDEN/FRUIT/DISEASE/oakrootfungus.html) and Phytophthora root rot (http://www.ipm.ucdavis.edu/PMG/GARDEN/FRUIT/DISEASE/pchphytoph.html). However, I have to stress that your photos seem adequate to show that your plants do NOT have these serious diseases.
My money is still on weather damage, unless you are seeing permanent defoliation on whole branches or many twigs! If the trees refoliate completely each year after fairly minor leaf loss in early to mid spring, that may just be a normal response to our climate.
You have set an interesting question.
There are many fungal, and a few bacterial diseases that are collectively called leaf spot diseases. Your trees have none of them (at least to any significant degree) because all cause deformation, discoloration, or progressive spot growth of the leaves. Your photos show healthy young leaves with some physical damage. Given that we've had light hail several times, and it causes symptoms exactly like your photos, and I've seen similar damage on other trees within a few miles of you, I'm pretty sure that is the cause of the leaf damage. Last year we had similar conditions; this is not uncommon.
That still leaves the question of the foliage drop.
Virtual all of the biological agents that cause leaf drop, as noted above, cause leaf deformation, discoloration, or progressive spot growth--your don't. Hmmm. In fact, one little known but critical fact in our work is that upwards of 95% of all residential garden problems are caused by abiotic factors: not bug or diseases, but either climate, poor plant selection, or "things people do"--like bad planting, over or under watering, over fertilizing, inappropriate weedkillers, etc. etc. Your photos show mature plants (so, not obviously poor planting), that don't show obviously bad pruning, in an apparently healthy lawn situation, with no obvious recent ground disturbance and no obvious pesticide (weedkiller) damage..... The most common villains do not seem to be actors here.
The critical question is: does healthy new growth completely replace the fallen foliage? If yes, whatever caused/causes the problem is transitory, and not serious (most trees can actually defoliate completely between 3 and 5 times in a year without causing permanent damage; that is obviously not what is happening here).
If, however, the die-back is permanent, with resultant bare branches or lots of bare twigs that do not re-grow new leaves, then the problem is more serious than freaek or unusual weather. Plums here can be susceptible to Armillaria root rot (http://www.ipm.ucdavis.edu/PMG/GARDEN/FRUIT/DISEASE/oakrootfungus.html) and Phytophthora root rot (http://www.ipm.ucdavis.edu/PMG/GARDEN/FRUIT/DISEASE/pchphytoph.html). However, I have to stress that your photos seem adequate to show that your plants do NOT have these serious diseases.
My money is still on weather damage, unless you are seeing permanent defoliation on whole branches or many twigs! If the trees refoliate completely each year after fairly minor leaf loss in early to mid spring, that may just be a normal response to our climate.
