I was browsing the old journal articles on Avocado Source (as one does), and came across this interesting study that was done in the 1960s on methods of rooting avocado cuttings, which I’d always heard is extremely difficult to do:
Basically, they found that the very youngest immature growth rooted with over 90% success in a misting chamber without bottom heat. Even slightly more mature growth (3 weeks older) had very low success rates, as did the groups that included bottom heat. Here’s how they described the type of growth they used:
They weren’t able to draw conclusions about whether rooting hormone helped or not because they didn’t control for that apart from in combination with the heating, and the heated ones virtually all failed.
I don’t have a misting chamber set up, but in light of this I’m thinking it might be worthwhile to build or buy one…
@Bradybb I know you have one, any interest in trying to root some cold-hardy avocado cuttings? My Poncho and Brazos Belle are both just starting to push out new growth that will probably be at the stage they described in a couple weeks.
Great! I’ll reach out in another week or two about meeting up to give them to you. I definitely owe you after your generosity in the last trade! It’ll probably be just ~2 Poncho and ~3 Brazos Belle cuttings.
An even more detailed study around the same time found drymifolia varieties often root more quickly than guatemalensis or americana, and their study showed bottom heat does help (but their baseline temperature was a lot lower so that makes some sense):
I had forgotten I’d posted this thread, but it seems like the right place to summarize my somewhat successful efforts to root avocado cuttings over the last couple of years, in case anyone wants to learn from this experience (or add their own experiences trying similar techniques).
Shortly after starting this thread, I began trimming and saving the tops I removed from rootstocks during grafting, and tried various methods of rooting them, including:
Placing them in a glass of water and change the water occasionally (they callused fine but never rooted)
Placing them in potting soil with no humidity dome (mostly they died)
Placing them in potting soil with a humidity dome (more than half still died, but a few rooted)
Placing in the back of an aquarium filter where the filter pad usually goes until callus, then into potting mix with a humidity dome (high rate of success in 6+ months)
Here’s my somewhat up-to-date list of the current successfully rooted (or suspected to be) cuttings so far, minus a few that I killed from frost damage and not yet including a few that I suspect have rooted this spring.
One thing I haven’t yet tried is either hydroponic or aeroponic rooting techniques, so that’s next on my list.
I just updated some of the photos in the link above, I realized some hadn’t been updated in almost a year. Both of the Aravaipa clones are still very small, almost exactly one year from when I cut them and this is after one new flush post-rooting:
If you click the little photo reel icon next to any of them, you can see all the photos associated with that particular tree. Unfortunately that doesn’t mean I’ve actually done a good job documenting each one, but some of them show the roots when they were first potted up, like this Aravaipa clone:
It was a shoot that I removed from the base of the winter-killed stump last spring, which had no roots at the time but has plenty now! Here’s the ortet (#51, a seedling of Mexicola Grande) regrowing from yet another winter dieback:
Fuerte is not a pure Mexican-race cultivar, it is a hybrid with Guatemalan genetics, so that would align with the published experiments that showed only Mexican-race cultivars root well. Did you use scionwood or fresh growth with leaves intact? Scionwood with leaves removed will fail 99% of time.
Grafting is definitely better in most cases, but for those of us engaged in extreme zone pushing, winter dieback is common, and even low-grafted trees may die above the graft in a bad year. Also, rootstocks may be less hardy and die even where the scion survives. I’ve had that happen a few times, where the grafted variety starts to leaf out but shrivels as it runs out of energy because the rootstock trunk is dead for a few inches between the roots and scion.
So, I agree that grafting is the industry standard for a reason, because avocados are easily grafted and grow vigorously. But there are use-cases where own-roots clones would be a better choice even if it’s a much longer process with lower success rates.
I took some cutting in the 1st of April. It was at the parking lot with an overgrown avocado tree. Not even sure what type it’s. Give it some growth hormone and stick in the soil with plastic bag over it. I checked a few of them after a month and no root. Checked some more in 2 months and nothing. Some grown new leafs, but still no root. Some die because the plastic bag collapse during hot weather and it case mold to grow. So, I putted some sticks to hold the plastic bag. Some still survive to this day, but I got tire of checking for root. If it survived to fall, then I guess it should have roots hopefully.
Good, because I have already stopped checking and good to know that it will take longer than some Youtuber video. I have grown roots from apple cutting and nectarine cutting. The Mulberries was the easiest of them all. 4 out of 4 was successful and 1 even have fruit on it and flowers while able to grown roots.
Since i don’t have a misting chamber either when rooting cherries etc. the way i do it is using a mason jar turned over on top of the cutting. It takes about 12-16 weeks to root cherries. The jar over the top of the cutting controls humidity. Typically i root cherries in river sand and use clonex rooting gel.
Unfortunately, most of the YouTube and TikTok videos about rooting various things are fake and just made for the clicks. There are also legit ones, but it can be hard to be sure which is which.
I do the same thing! For avocados, I usually remove that around 3 months and instead water often (daily) to encourage hardening off and new growth. Some die immediately then, but I figure by then if they aren’t well-callused enough to survive jar removal then they probably never will.
Here’s a great example of “don’t give up on avocado cuttings just because they haven’t rooted yet” for you. I took this cutting from an outdoor rootstock (the seedling of “Purple Nebula” that Poncho is grafted on) back in mid-December and it’s just now pushing new growth, and strongly enough that I’m confident it has roots: