Three weeks ago, I finally removed a failing vine and replaced it with one of the back-up vines. Last week, I wrote about my attempts to determine if the stunted canopy growth of the failed vine was from scion or rootstock. What I didn’t talk about, not in much detail anyway, was what I found below ground.
Not only was the root system of the failed vine undeveloped, but there was a robust root (reminiscent of that on the healthy replacement vine) running through the spot where the failed vine stood.
1103 Paulsen rootstock is a cross of V. berlandieri and V. rupestris. It is generally drought tolerant and works well in hillsides. I have no idea how quickly or robustly it grows, but I was concerned that this root could be from a neighboring vine.
I asked Sam Caselli at Novavine if any of the neighboring vines (six feet to the closest one in the same row, and eight feet to the closest one in the next row) could have developed roots this far-reaching since being planted three and a half months ago. He did not think this was the case.
There are many plants which have extensive root systems or spread through rhizomes. It is most likely that these roots were part of another plant. However, the spot where these vines were planted was fairly clear of plants with the exception of some small weeds and shrubs.
The reason I am so concerned with the origin of this root is that I ultimately decided that it likely does not belong to any of the neighboring vines. So I cut it out. I wanted the new vine to have as little competition for resources as possible. Three weeks out, the adjacent vines appear to be doing fine.
What made me do a mental double take was looking at the photographs of the pulled and replacement vines’ roots. There was something in the picture of the replacement vine that I had seen and paid attention to when putting it in, but it didn’t click with something I’d heard in the past until I was looking at the photographs:
There were two sets of roots on the replacement vine (image below).
There was the main root ball, which had developed from the roots the plant had on arrival (“set 2”) and a second set, about six to eight inches higher, which consisted of two long and robust roots extending laterally from the trunk of the root stock (“set 1”). When I planted the vine, I made sure to keep this higher set separate and above the lower set, keeping them as horizontal as possible.
Reviewing the day’s photographs, a vague recollection of someone telling me that grapevines have two sets of roots with separate functions began to develop. Of these two sets of roots, I seemed to recall that: the primary function of one set is to anchor the vine and the function of the other is to seek and draw in nutrients.
I was not concerned that these higher roots belong to the scion. The vine had been planted in a relatively shallow container and the graft union was well above the soil line.
I called a few people, sent a few emails and did some pretty intrepid web searching. Finally, Sam Caselli explained that grafted vines have “tap roots” and “feeder roots”. Tap roots develops from the root system in place when the grafts arrived and generally grow straight down, to to anchor the vine. Feeder roots can originate on the tap roots and grow horizontally in search of nutrients. They can also arise above the original root ball and grow horizontally as well. This is what is most likely the case.
Just like the “tongue map”, the idea of two distinct root systems with separate function is not likely, but it is possible that one set may carry a greater burden of one task over the other. I think I’ve gone as far as I can with seeking answers about the nature of these roots. If any reader has additional information, I welcome it.