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Cold-hardy avocado breeding for the PNW

Seeking to find the hardiest Mexican-race avocado cultivars and landraces available, then interbreed them in a greenhouse and trial their seedlings in zones 8-9 in the Pacific NW.

Currently we have ~20 cultivars on multi-graft greenhouse trees, ~50 seedlings, and we are looking for new cultivars and volunteers to grow seedlings and grafted trees in this region. Cultivars that reliably produce hardy seedlings will be hand-crossed in our greenhouse to provide seeds for the project, and any seedlings that flourish will be grafted back onto the greenhouse trees to be included in the breeding pool. High mortality is expected initially, but hopefully as the project progresses that will decline in future years.

Researcher background
I have no formal horticultural training, but have spent the last three years reading avocado research papers, collecting and grafting specimens, collecting and germinating seeds, and visiting marginal areas where avocados are grown in backyard settings to learn what the greatest challenges will be in our cool & wet climate.
Are you seeking volunteer growers or other types of volunteers?
Yes, seeking volunteer growers
How many volunteers do you need?
What will you ask volunteers to do?
Volunteers who live in other marginal climates where avocados are occasionally grown will be asked to locate hardy specimens and provide cuttings. Volunteers in this region will be asked to plant seedlings or grafted trees and provide updates on their health periodically, as well as cuttings from any especially successful seedlings.
Is this a multi-year project?
Can volunteers expect to be able to keep some germplasm (seeds, bulbs, cuttings, spores, etc) at the close of the project?
Yes, of course
Researcher Location

United States

Project Updates

Surplus 'Bacon' trees to give away ...

project update by
Sunday, February 25, 2024 - 05:37

It's quite likely that I'll be giving away 3 out of the 4 remaining 'Bacon' trees that are growing outdoors, here in SE England. Please email me if interested to I'm giving them away as I want to keep only one individual of each 'variety', due to a limitation on space.

These trees are only available to UK residents (you'll need to provide your own transport), due to the complicated administration & costs involved in exporting live plant material with soil.  I'll contact anyone interested around April time (spring is the best time for transplanting), to arrange collection.

If you want further detailed information on this plant material, see entries (19), (20) and (21) at

Reminder about tree distribution instructions

project update by
Thursday, February 1, 2024 - 06:27

Greetings! I have noticed a few new people have joined on the EFN project page, but have not also joined on our website. Thank you for your interest! However, if you are located in the project area (lowlands of Cascadia), and you wish to receive trees, then you also must sign up on the website, as that is the list that I use for assigning trees. This is now a two-step process, as explained below, and please do so ASAP if you wish to be considered for trees this year, as I will be doing allocations in just a few days. Based on the current response rate (29 members requesting trees this year) and the number of currently available trees (55), it is unlikely anyone will receive more than two trees, and many members will only get a single tree. I expect to have up to twice as many trees in 2025, based on current inventory of seeds and fresh seedlings just now germinating.

To receive a tree, you must first "join" the project, at this address:

Once you have done that, you must specifically RSVP to receive trees this year (since many members are out of the region or do not have space for trees at this time, it is a separate form):

I am requesting that if you are able to, members come to pick up the trees here in Seattle on one of the dates listed there. I will be making a few deliveries, however, and some other members may be recruited to do the same, so please do reach out via email at if you wish to receive trees but are not able to pick them up on any of the available dates. If you wish to come to Seattle on a different date, I may be able to accommodate that as well, so just ask.

Best wishes,


Growing Avocados at 50.865°N ...

project update by
Wednesday, January 4, 2023 - 06:16

I've joined this group as I'm keen to exchange information and experiences on growing avocados outside of their usual geographical range. I grow all my trees outdoors, in the ground, in a coastal climate in southeastern England (UK). All avocado material has been raised from seed and grown on its own roots. I have eight trees, the oldest is almost 6-years-old, the youngest is less than a year old.

I'm particularly interested in obtaining a couple of seeds of Aravaipa or one of the other Mexican types. Here are links to my blogs, updated continuously whenever I have new photos or interesting observations to share:




'Del Rio':

My background is in horticultural research, specializing in the adaptation of plants to environmental stress for 20 years (physiology & biochemistry) and worked in UK, Europe & N. America. Now retired, I still follow this interest through some of my gardening activities, i.e. attempting to grow crops outside their usual geographical range, with a particular interest in avocado, and possibly citrus (satsuma).

EFN update form causing broken links

project update by
Monday, November 7, 2022 - 07:09

It looks like that last project update had HTML special characters inserted into the body of the message by the EFN update form every place where I hit the "Enter" key. Unfortunately, that broke the sign-up link. If you visit the EFN project page and view the update online, the link is functional, and I will try to insert it here one more time: ... Thank you again, and I look forward to getting in touch with each of you once you sign up. Happy growing! - Winn

Sign-up form has gone live!

project update by
Monday, November 7, 2022 - 06:48

Greetings, fellow avocado enthusiasts!

It has taken a bit longer than I had hoped to get the new version of the website up and functional (for the most part... I hope!), but you can finally officially join the project and request your tree(s) at this URL:

I will follow up directly with all new members in the next month or two to coordinate tree deliveries this coming spring. If you have any questions, or if you run into any technical difficulties on the website (very possible!), please email me at If you are outside the geographic area where I will deliver trees, feel free to join anyhow but understand that you will probably not get a tree in the first distribution next year.

Other parts of the new website are still under construction, and the photos and information for the tree database are in dire need of updating, but feel free to peruse those sections as well.

Best wishes,


Timeline for tree distribution

project update by
Friday, August 12, 2022 - 03:20

I've had a few questions recently about when volunteers should expect to receive trees.

In short, a link will be sent to all participants during the fall or early winter (November-ish 2022), allowing volunteers to provide details about their rough geographic location and the number of trees they hope to adopt/host. That link will also be added to this profile once it goes live.

In order of registration, volunteers in our research area should expect to be contacted over the winter to coordinate delivery of their tree(s). The first trees will be distributed in late spring of 2023, and new trees will be distributed each year thereafter around that time of year. The number of trees available should increase each year as our breeding trees grow larger and produce more seed, but the first distribution (2023) will include only a couple dozen trees.

As casualties are expected to be high in early years, priority will be given in later years to those who need to replace dead trees.

Please direct questions to info(at) drymifolia(dot)org.


project update by
Thursday, August 11, 2022 - 07:42

I am interested in following this project in order to maybe learn more. I don't know if i will be of much practical help because i live in brittany, france. I am trying to grow avocadoes outdoors where i live. The climate where i live is comparable to the pacific northwest. I have one mexicola and one fantastic seedling growing outdoors.
My findings for now are that they die back down in winter but regrow from the roots the following year.
Only by protecting them can they be prevented from dying in winter. I don't fully understand the exact reasons but temperature is only one, and not the most important, factor.
I have another fantastic seedling that i planted in my polytunnel and it survived the winter just fine despite having been exposed to the same temperatures, but protected by the polytunnel.
Young avocado plants seem to really dislike the long weeks and months of cold moisture descending down and freezing on their leaves if grown outdoors