Highbush Cranberry Viburnum large leaves

Question: I planted 3 Highbush Cranberry viburnum about 30 years ago. Over the years they have sent up lots of new shoots and even suckered somewhat. We occasionally have gone in and removed old growth and all seemed normal until this year. We're noticing some branches that appear to come from the same source, but have super large leaves. If the original were roughly 2 1/2" from top to bottom, the leaves in question can be as big as 6-8". We're trying to figure out if there's actually some different plants/vines somehow mixed in there, but every time we follow the stem it seems to lead back to one that we know is original and has the smaller leaves. I don't remember this ever happening before. Could we have an imposter mixed in somehow? Or do plants under stress sometimes create really large leaves? 

I've enclosed a picture that has a regular branch circled in blue and 2 questionable leaves circled in red.

responder: An Ask Extension Expert Replied July 24, 2023, 12:09 AM EDT
response: Thanks for your question.  Quick question first for you. Have the questionable leaves, circled in red, developed any berries?  If so, what color are they?  Looking forward to your response. Many thanks!

responder: The Question Asker Replied July 24, 2023, 9:26 AM EDT
response: I could have sworn that I’d seen berry clusters on at least one of the big-leaf stems, but my husband did a little cleanup yesterday so I can’t verify that - and it’s very possible I’m wrong. I took a couple more pictures and will try attaching them here for you. The bark on the stems looks very similar to th viburnum, but the new shoots are coming out large and green and almost seem to have small ridges. Also, the deer (or other pests?) have been ignoring the small leaves of the viburnum, but have been going after the large leaves. Sent from my iPhone On Jul 23, 2023, at 11:09 PM, Ask Extension <<personal data hidden>> wrote:﻿

responder: The Question Asker Replied July 24, 2023, 9:26 AM EDT
response: I could have sworn that I’d seen berry clusters on at least one of the big-leaf stems, but my husband did a little cleanup yesterday so I can’t verify that - and it’s very possible I’m wrong. I took a couple more pictures and will try attaching them here for you. The bark on the stems looks very similar to th viburnum, but the new shoots are coming out large and green and almost seem to have small ridges. Also, the deer (or other pests?) have been ignoring the small leaves of the viburnum, but have been going after the large leaves. Sent from my iPhone On Jul 23, 2023, at 11:09 PM, Ask Extension <<personal data hidden>> wrote:﻿

responder: An Ask Extension Expert Replied July 24, 2023, 9:52 AM EDT
response: Thanks for the question. The plants you circled in your picture – red and blue – are both European Cranberries (Viburnum opulus). These specific species are representatives of a larger group of cranberries known simply as Highbush cranberries. See: https://extension.umaine.edu/cranberries/highbush-cranberry/ https://trees.umn.edu/highbush-cranberry-viburnum-opulus I don’t have a good answer (at least in my mind) as to why on this single bush you are getting leaves of different sizes. From your question it is not clear to me if you are seeing these two different sized leaves on all three of your bushes or only one bush. We have been having stresses of high temperature and limited moisture. I doubt that these would lead to alterations in leaf sizes. I suspect that the variety of cranberry you have is either americanum or opulus (also known as a Guelder-rose cranberry These are the two most common varieties sold in the Metro Area. Descriptions of this variety indicate that its leaves are between two to four inches long. This is consistent with the size you indicated for the leaves circled in blue in your picture. The opulus variety can grow more rapidly and in certain areas is considered to be invasive. Its berries are sourer than the americanum variety. See: https://ipm.missouri.edu/MEG/2021/11/cranberry-MW/ The explanation for your situation might be your bushes have been grafted. This was more common in past years than now. You did indicate your bushes are over 30 years old. In a graft, a cranberry bush capable of good root growth is first selected as a “rootstock”. It is what gets placed in the ground. To this rootstock is grafted a slightly different cranberry – termed the scion – that possesses certain desirable characteristics such as fruit flavor and development. Often the site of the actual grafting can be recognized by a swelling near the base of the plant. Take a look and see if you might find evidence of this swelling. Look right at the soil line. Perhaps even dig down as often this grafting site gets covered with dirt over the years. Also look up from the soil line to about 6 to 8 inches to see if any swelling/enlargement is present. Here’s what I’m thinking. The larger leaves are growing up from branches originating from the rootstock. The smaller leaves are growing from the scion. This is why it would be important for you to look for this grafting site. Branches coming up from the root stock (large leaves) might not be expected to develop any berries. Also branches coming up from the root stock would also be expected to have a different bark texture than branches from scion. This is consistent with your observations. The key to this puzzle is whether or not you will be able to see evidence of a grafting site. After 30 years it may not be visible. Regardless, I would suggest you just prune out the branches that have the larger leaves. See: https://www.thespruce.com/grafting-glossary-scion-and-rootstock-3269516 Good luck. Thanks for using our forum.

responder: An Ask Extension Expert Replied July 24, 2023, 10:05 AM EDT
response: One additional thing. I can’t give you a positive identification for the white material on the leaves. It could be wooly aphids but I can’t find evidence that such aphids infect high bush cranberries. It could also be evidence of a fungal infection. In any instance I doubt that it be harmful to your cranberries. Just remove and discard these leaves. See: https://www.goodhousekeeping.com/home/a46291/asian-woolly-hackberry-aphids/ Thanks again for using our forum

responder: The Question Asker Replied July 24, 2023, 6:28 PM EDT
response: Thank you, this totally makes sense!!! One of these days we’ll get in there and see if we can identify the grafting site and confirm – but I’m convinced that what you suggest is exactly what’s going on.  Our house is on a lot that was originally pretty swampy and we’ve fought all sorts of invasive species. I was worried that we might be on to another one that might prove difficult to tackle.  Thank you so much! From: ask=<personal data hidden> <ask=<personal data hidden>> On Behalf Of Ask ExtensionSent: Monday, July 24, 2023 9:09 AMTo: marykiel <<personal data hidden>>Subject: Re: Highbush Cranberry Viburnum large leaves (#0112154)

responder: An Ask Extension Expert Replied July 24, 2023, 7:14 PM EDT
response: Glad to have been of assistance.  Thanks again for consulting us.