North American Fruit Explorers mailing list at ibiblio

["Griffin Gardens" <griffingardens@earthlink.net>]

Hi Kevin,

   I am an amateur too and I think maybe we didn't go the same school together, but we must be reading different books and seeing different things in the orchard and nursery. Maybe this explains some of that. As you know everything gets compressed here in the north - bloom time and pollenizers for cherry cultivars, for example,  is a big issue in the warmer climates while here they all bloom at roughly the same time - as soon as it is  finally warm enough to start growing. Last year I experienced that southern phenomenon  with my Moongold and Sungold cots when we had an unusually warm April and an equally unusual cool May. This extended the bloom time so that Moongold, usually a day or two ahead of SG, was completely finished before Sungold opened a blossom, something that David Bedford at the Uof MN told me he had never seen before. The same thing happens in a warm wet fall - everything, (except for natives) regardless of variety or rootstock grows too late into the fall and is susceptible to frost injury when winter comes crashing down. On the other hand, in a dry cool fall, senescence begins earlier for everything and  the varietal and specific characteristics of the trees are allowed to express themselves. It is under these conditions that I see the rootstock influence, not when it is overridden by climate.

  Try this for rootstock influence on budbreak: I had the same apple variety grafts on different rootstocks next to each other in the nursery row this spring. The one on Siberian crab broke bud a good 8 days before the one on V-1, and other varieties on Siberian were also earlier than anything else. I don't do much with apples, but I thought this was noteworthy.

 

Dave

 

Dave

----- Original Message -----

From: Kevin Bradley

To: nafex@lists.ibiblio.org

Sent: 8/4/03 8:12:29 AM

Subject: [NAFEX] RE: Topworking

Dave, from MN wrote:

I think the main benefit from having a hardy understock for a
tender
tree
> is induction of early dormancy of the cultivar by the rootstock.

I have never seen a rootstock induce early growth in its grafted  cultivar and so perhaps falsely assumed that it would not induce early dormancy. I will check this this fall on my topgrafted peaches on p americana compared to those on maheleb.
I have seen a ranetka sucker break bud under a dormant Sweet 16 that broke bud exactly the same time as those grafted on antonovka that is, about 10 days later on average. In other words, the rootstock had absolutely no influence on the bud break of the cultivar.
I am nearly convinced that the main advantage to topworking is the "tender crotch/trunk" theory, that is that the weak links in deep winter cold endurance are the crotches and trunks and not the outer branches. I don't think I buy the "inducement" theory (of inducing hardiness from hardy frames to tender grafts.)
There were some recent experements on this but very poorly conducted planned and inconclusive in my opinion.
I speak, BTW, not as a plant physiologist but as an amateur who reads a lot on this subject and who makes observations in the nursery.