I’m planning to dive into the process of growing avocado trees and I’d like to understand more about the use of clonal rootstocks. I’m hoping someone here with more knowledge or experience will be able to speed up my learning process.
First, regarding the clonal rootstock—I’m trying to find a source. It seems difficult to find small numbers of the good rootstocks (they are only available wholesale). I think I’ve found nursery where I can buy trees on some of the premium rootstocks (for example a Hass tree on Dusa rootstock). If I cannot find the rootstock alone, could I just get the sapling trees with the good clonal rootstocks and then cut off the upper scion wood to just leave the rootstock? Would the rootstock grow out in that case to essentially create a tree of rootstock material (a Dusa tree for example), or would the tree not survive that type of severe pruning? My goal with this would be to grow out a tree for future use as rootstock scion wood.
Second, regarding the cloning process—this appears to be the basic process: https://youtu.be/FVEP11S1Nuc?si=eQPjdU-TqUOGm7Ak
I understand the use of the nurse seedling. Once the rootstock scion has been grafted into the nurse, is the darkroom really necessary? The Brokaw website doesn’t mention the darkroom step—it looks like a standard airlayer: Rootstocks - Brokaw Nursery, LLC
Are avocados difficult to airlayer?
Here is another nursery photo showing what appears to be a standard airlayer to grow roots on the rootstock scion:
Before digging into the rest: why do you want clonal rootstocks? They are really only needed if you have soil that’s particularly bad for avocados, such as pure clay, high salt content, or a high water table (wet feet).
Otherwise, most avocados are sold on seedling rootstocks, which work fine in most circumstances.
Aren’t the clonal rootstocks protected by breeders rights? That would make it impossible to sell them yourself commercially. I would check that first.
The process of cloning rootstocks has demanded a lot of research and is not simple. I would imagine that Brokaw has invested a lot in the techniques and only sells to wholesalers because they are the ones that really need these rootstocks, in order to project their harvest over the coming years in relation to their investments I guess.
I doubt that they would be that important for home growers, who can use seeds as rootstocks and replace the proportion of trees that do not perform as wanted.
They should regrow, as long as you are certain you’ve accurately identified the graft union and cut below that (and not, say, the scar from the top of the original scion, which can sometimes also look like a graft union). Avocados aggressively sprout from the root ball when they are cut or frost-killed at ground level.
Yes, I’ve had zero success attempting air layering of avocados. I’ve had better luck with rooting cuttings (though they need to be a different kind of cutting from scionwood, with hardening leaves intact). The etiolation of the lower stem is necessary to initiate roots, but it can be within a tube rather than in a darkroom. So what you’re calling air layering, as long as it’s a light-blocking tube rather than clear plastic or something.
Most of them are not covered by live patents, in the U.S. at least, but some of the new ones might be so that’s definitely something to consider. There may be trademark issues for some that use a trademark name rather than a cultivar name (Dusa is a trademark name, I think, for example). You just have to use the cultivar name instead of the trademark name, for things that are trademarked but no longer patented.
I checked Dusa® and the cultivar name is ‘Merensky 2’, the patent expired in 2021:
So if you were to buy something grafted on Dusa® and successfully cloned it, you’d have to call it “Merensky 2” but could probably say “same cultivar as Dusa®” (though this isn’t legal advice and maybe you’d want to get that first).
I think that’s what those “air layer” sleeves are in the Brokaw photos you posted above. It’s okay for the top to have light as long as a significant part of the stem is covered.
I had missed this part. I don’t necessarily recommend Mexicola seedlings as rootstocks. They often grow with low vigor in the first year and tend to have thinner stems that might not be suitable for grafting until months or even a year later than some better seedling rootstocks like Duke, Aravaipa, and especially Zutano and Bacon.
There’s a reason so many retail nurseries and even many wholesale nurseries use Zutano and Bacon seedlings as rootstocks. They grow vigorously and have nice thick, sturdy stems. Unfortunately, both of them seem to struggle with cold soil temperatures in winter, and often fail to sprout in spring here in Seattle. I’ve had nearly 100% root survival for Duke seedlings and more like 10-20% for Bacon and Zutano. But Seattle’s long duration of barely-above-freezing temperatures is somewhat unique, so it likely isn’t an issue in most avocado zone pushing areas.
Fruitwood sells good graftable sized Bacon and Zutano rootstocks for pretty low prices, usually in sufficient numbers that they are in stock for a few weeks after the scionwood sells out. Their owner did also tell me they hope to start offering other avocado seedlings when their nursery trees get large enough to produce sufficient seeds, but they didn’t give me a timeline.
I am growing some Mexicola seeds and they are definitely slow. They are the easiest to find seeds in the 16-20F club which includes Duke, Aravaipa, Wilma, Del Rio etc. I did find some Wilma seedlings for sale locally but I’ve been watching everywhere and it’s so hard to find seeds from this group.
I’m hoping my Aravaipa fruits next year. It’s 6 feet tall. My Duke is only 3 feet tall and my Mexicola 5 feet.
I think the best thing OP could do is to buy some trees of the above types and then offer the seeds for sale later. Avocado rootstock is constantly talked about on the forums yet cold hardy seeds are nearly impossible to find.
Not yet, though the largest Duke graft is about 9’ tall on its third year since grafting, and it set a lot of fruit this year but they all aborted while pretty small. Maybe next year! Here’s the graft union for my largest Duke graft:
I’ve gotten Duke seeds from Marta Matvienko a couple times, but not since fall 2022. She lost access to her Duke tree and is working to get another one established in her new orchard.
The two old trees are still in the old Oroville train station, which is now just a parking lot for a restaurant. It’s even publicly flagged as “Duke Tree” in Google maps:
Yes I’d heard that these trees were in Oroville. Has anyone from this forum harvested fruit from them? I wonder if the restaurant owners would hassle me.
I’ve seen photos of multiple people climbing in the trees and none of them mentioned anyone bothering them. The trees are kind of near the back of a big parking lot next to the railroad tracks, I’m not sure why they’d care about people visiting them unless you started harvesting them as a commercial operation or something.
I don’t think anyone will bother you. I’ve visited the tree two times now. Lots of spots people have cut scionwood from. As long as you don’t go too crazy the only possible run-in is probably with a homeless guy from the bushes across the tracks.
Yes I’d heard that these trees were in Oroville. Has anyone from this forum harvested fruit from them? I wonder if the restaurant owners would hassle me.