Looking over old threads on the forum I have found several cases in which members describe grafting otherwise desirable fig varieties that have some drawback (cold sensitivity, FMV, lack of vigor etc) onto a rootstock from a variety that does not exhibit the given "defect".  There has been some discussion on what the effect of this would be.  For example, if a cold sensitive fig has a rootstock from a cold hardy variety would the entire plant exhibit the cold hardiness of the roots? Or would the shoot portion of the plant exhibit the cold sensitivity that is characteristic of that variety resulting in a plant that freezes down to the graft?  There has been a bit of debate about this.

So my question is whether anyone has actually compared side by side the cold hardiness of a cold sensitive variety not grafted vs. the cold sensitivity of that same variety grafted onto a cold hardy rootstock?  If there is evidence that there are benefits to this then this is something I will definitely try this year.  Of course I realize grafting can be used for other purposes like making a 3-in-1 tree and getting cuttings going sooner but what I really want to know is whether it improves a characteristic of the mature above-ground portion of the plant.  Thanks!

My experience is not with figs but here it is anyways.

Years back I bought a grafted heartnut tree from Grimo's nuts and it died right back to the graft union the very first winter. But the rootstock portion above ground continued on to grow and make it through the winters. I was living in zone 4b/5a at the time.
So the rootstock did not make a difference in the hardiness of the scion.

Sam, that's useful information.  I wonder if there is any reason to think figs would be different?  I would guess not.  My main interest would be in improving cold sensitivity but I imagine with FMV the results may differ depending on the specific varieties being put together.

I am NOT saying that there is not some synergy between the rootstock and the scion, but the scion continues to have the genetics of the scion, so I would expect the rootstock to have little affect on cold hardiness. I would tend to doubt that a organ transplant from a person who was always hot would have any affect on a person who was always cold. Where there might an expected benefit would be with poor growing varieties being grafted onto a vigorous growing rootstock. Most rootstocks are chosen for their soil characteristics, that is, what kind of soil they thrive in, such as heavy clay, or wet soils, etc.

I believe that Grasa's use of her rootstock selection is that it shows vigor in cool weather, not that it is cold hardy.  There are many rootstocks of different species that show the ability to tolerate wet soil conditions, etc.  The genetics of some varieties producing good fruit quality may also result in roots of low vigor so I believe the case can be made that we might find some very good benefits from grafting those varieties onto rootstocks of more vigorous varieties.  That is what I hope to test with grafting Black Madeira to Brown Turkey. Until just a few recent efforts at this in figs, I'm not aware of any efforts to analyze any such benefits.  We are fig pioneers.  Small fig pioneers, but still fig pioneers. :)

So it sounds like there is probably little or no advantage in switching rootstock to enhance cold hardiness but there most likely is an advantage in terms of adjusting growth rate up or down.  Daniel, I hadn't thought about adjusting growth rate down but this would make a lot of sense for many who don't have a lot of space and live in mild climates where the fig trees can get quite large.

Jon, regarding the cold hardiness issue, I'm sure others on this forum know more plant phys. than I do but I thought I read somewhere that the properties of the sap determine in large part the cold hardiness of a variety.  I'm not sure which tissues produce the components of the sap that confer cold hardiness but if the roots produce at least some of these components (and they get transported throughout the plant) then it would make sense that the cold hardiness of the roots could influence the cold hardiness of the shoots.  Sammy's post would seem to cast doubt on this though.  There's a lot of "ifs" and speculation in this paragraph so it would be cool if someone has actually made the direct comparison. 

- Rewton. This is a work in progress for me. I've been grafting figs for a couple of years now. My initial purpose for grafting was simply to give some "special" varieties the best chance at making it. I was also hoping to get as much growth as possible out of the scion in the first season. 

The next season I still had the above goals in mind but with the added goal of grafting less vigorous varieties onto more vigorous rootstock. The two scion types I used are also suspected to be greatly affected by FMV - Black Ischia and Black Madeira. My results were favorable but not really stellar - yet. The rootstock I used was "Brown Turkey" that I bought from Tractor Supply. Although the rootstocks were real nice looking plants, I wasn't all that impressed with the vigor they showed. I have some local unknowns that seem to show better vigor.

I plan to repeat some more tests this spring using Black Ischia. I will be using one or two rootstocks that I know are vigorous and also do great in my local soil conditions. At least one of these also seems to be pretty cold hardy here in zone 6b. I'll try to use this one as much as possible but I'm limited by the quantities I have of that one. I also have a piece of Pastiliere (as well as a couple others) that I plan to graft.

I've never been real "scientific" about keeping records on my experiments but I'll try to pay closer attention to these little projects. Since pics are such a great way to preserve a record of progress, I'll try to do as much of that as possible at least.

I am also interested to see if the rootstocks will have any effect on cold hardiness. I'm thinking not, but time will tell I suppose. I think this aspect will take a few seasons to really prove out one way or the other. Even then, this may be the results based on only a couple of varieties - including scion as well as rootstock. Bear in mind, just because a graft fails after one season out in the cold, doesn't necessarily mean it was due to the cold. 

Please keep us posted on your successes as well as failures ;-) . It's a lot of fun experimenting isn't it?

Bill, thanks for your interesting post.  As you obtain more information from your experiments please let us know what you find out!  I'll do the same but you are right that these are multi-year experiments.