The Legendary Duke Avocado, Part Deux

Sunday, October 28, 2012

Duke Avocado Trees: Old Oroville Depot
An avocado tree that can not only withstand freezing conditions but laugh in the face of a one Mr. Jack Frost himself? An avocado that offers a higher oil content than the Hass? An avocado variety that can withstand root rot conditions that have doomed other trees in the Bird Back 40? Say it ain't so! I must have one!

Consider this a followup to a journey that started many moons ago during that one night where I could not sleep. I was desperately seeking Susan, err, for an avocado variety that could withstand our colder than cold Northern California winters. It was that night that I discovered the Duke, its ability to withstand freezing winter temperatures and its interesting history, which I wrote about several months ago.

Introductory Garden: Old Oroville Depot
The posting about the Duke has generated the largest response from readers since Venus and I painted a beehive Hello Kitty pink and proceeded to get stung silly while attempting to become amateur beekeepers. That's a good word: Amateur. Another good word is foolhardy. But I digress.

The quest to grow an avocado tree in our micro-climate cold North Natomas Back 40 by reaching back into Northern California history to grab a bit of the past has been an interesting journey indeed. My singular attempt to bring this 100-year old variety called the "Duke" into the present day has now grown to involve the efforts of several growers, some connected with California Rare Fruit Growers (CRFG) and some not.

First Graft Attempt: FAIL!
When I signed off on the last posting, I was attempting to graft Duke scions onto three different avocado root stocks provided by David Johnson, an avocado aficionado who has painstakingly turned his Waterford backyard into a rain forest-like shrine to all things citrus. If you think "you can't grow that here," David is probably growing it, and growing it successfully.

And now? The rest of the story.

I suck at grafting. I really do. It's a skill that I've not yet acquired, despite some early grafting success that I experienced last spring with my pluot and plum trees. Grafting stone fruit scions to other stone fruit trees is MUCH easier than grafting citrus, a painful lesson I would learn after watching every single avocado graft I attempted curl up, turn a none-too-pleasant shade of black and DIE.

After watching my repeated grafting attempts fail and fail and fail again, nearly destroying three avocado root stocks in the process, fate would smile upon me rather fondly. A fellow avocado NUTCASE like me learned of my struggles and advised: "Contact Sam."


Venus Beneath Monster Duke Avocado Trees
"Sam" is actually a nickname for a one Samad Janfeshan, who lives in a quiet Arden Oaks Vista neighborhood. I would later come to find out that Sam is quite famous, provided one of your primary languages is Persian. I am told he still takes phone calls from all areas of Europe and the Middle East thanks to his knowledge and experience in the field of all things horticulture. As I would come to find out, Sam employed a highly successful grafting technique learned while tending the family ranch in Iran.

How did "Sam" get from an orchard in central Iran to Sacramento? That's a story even more interesting than his grafting technique and a backyard that is a shrine to his marvelous grafting abilities. Like many Iranian citizens, Sam was fortunate enough to attend our institutions of higher education in California. Unfortunately for Sam, during this particular period in time, things got a little crazy in his home country.

Ayatollah Khomeini
It was during this time that the Shah would be overthrown, the U.S. embassy would be raided and hundreds taken hostage and a figure known as the Ayatollah would come to power. Overnight, a once-staunch U.S. ally in the Middle East would become decidedly anti-American. Sam, who watched events unfold from the safety of California, decided he wanted no part of the new direction his country was headed in and worked to become a citizen of the United States. He would give up the farm, but never lose his love for fruit trees and other horticultural endeavors.

I am more than fortunate to be steered in this man's direction. He saw the troubles I was having. He scolded me silly for my amateurish grafting attempts and proceeded to teach me a skin-grafting technique that I've never seen performed before. It's a technique that has resulted in multiple plum, mulberry and other fruit tree offerings that grace the family backyard. Yet, you will find none of these varieties at your local nursery. You will, however, find them in Iran.

Duke Avocado Leaves: Brilliant Yellowish Green
It suddenly struck me that if Sam could successfully grow fruit trees native to Iran in the backyard of his Sacramento home, he could probably solve my grafting problems with the Duke Avocado. Call that a rather fair assumption. Every graft Sam attempted survived. Three sorry looking avocado root stocks have been transformed into legendary Duke Avocado trees.

Not satisfied with his success on three trees, additional root stock was procured from a long-time member of the Sacramento Chapter of the CRFG where Sam again demonstrated his successful grafting skills. Additional Duke scion wood was also farmed out to David Johnson and other CRFG growers who are slowly bringing this heirloom avocado tree back to life.


Freshly Harvested Duke Avocados
Although I've uncovered a lot of information about the legendary Duke line and discovered old Duke trees in locations scattered throughout Butte County, one big piece remained missing from this equation. What does a Duke avocado taste like? Was this variety abandoned so long ago because it tasted like the inside of one of my old tennis shoes? I had always strongly suspected that the Duke was abandoned by commercial growers because it was a poor shipper. But I couldn't prove that. Not yet anyway.

I would have to wait for Duke season that finally arrived this month. Duke trees are alternate bearing, which means in some years you get a heavy crop of avocados and other years the pickings are slim. 2012 turned out to be one of those lean years. As I gazed into the treetops of the Duke trees in the Oroville Depot Introductory Garden earlier this month, I found what I was looking for.

Fruit Harvesting Basket for Fat People
It was also 30 feet off the ground. While I was once a champion tree climber in my youth, quite a few years have passed since then, and considerable pounds have been added to my once wiry frame. I wasn't about to scramble up a tree -- avocado or no avocado. Fortunately I had come armed with a fruit harvesting basket like the once you see pictured, plus a handy dandy telescoping handle that put the Duke fruit well within my reach.

I can't begin to describe the joy and satisfaction I felt as I pulled that very first piece of fruit off this heirloom tree and brought it slowly downward. Months of reading, research and phone calls had finally resulted in this moment. Upon grabbing my first Duke avocado, I brought it up close to my ear and gave it a vigorous shake. This was the final test. If this was truly a Duke avocado, the seed would be loose inside the piece of fruit. You can imagine my smile when I heard that tell-tale "thunk-thunk-thunk" sound as the seed bounced around inside.

Loose Seed Pit: Duke Avocado
That tell-tale sign of seed thumping plus the thin green skin confirmed, finally, that this was the Duke Avocado. What was once lost had been found again. After pulling 20-25 avocados from the largest of the two Duke trees in the Oroville Depot, I departed for a nice lunch in the Western Pacific Brewing Company before embarking for home.


The first true taste-test of the Duke avocado would take place later that night as I presented the Duke haul to the avocado snob that is the wife that is Venus. The wife that is Venus knows her avocados. The wife that is Venus also has her own avocado TOOL for removing seeds and skins from the precious fruit. I would come to discover that this tool is useless with Duke avocado. It's designed for working with thicker-skinned varieties like the Haas, Mexicola and Fuerte.

Duke Avocado: Right-Hass Avocado: Left
As I watched Venus slice into the first of the Duke fruits, the first wave of doubt washed over me. This wasn't a soft, smooth, creamy avocado. Not hardly. The first taste of the Duke fruit confirmed the worst of my fears. It featured the consistency of a crunchy apple. It was also quite tasteless. What had gone wrong? Had I picked it too early? Was the Duke abandoned because it had the consistency of a rock?

Color me disappoint.

It was a few days later when I received a message from gardening friend Nels Christensen, who I had gifted with four Duke avocados. He messaged me to tell me that he was in the process of making guacamole. "GUACAMOLE!" How does once make guacamole with rock hard avocados? Nels messaged back to inform me that the Dukes had softened to the point to where they were pliable.

Creamy Delicious Duke Avocados
As it turns out, my worst fears were nothing to worry about. Duke fruit does not turn soft and ripen on the tree. Duke avocados are quite hard at harvest. But after picking? They ripen VERY quickly. In two short days my collection of apple-consistency avocados had developed the consistency of a squishy sponge. They were more than ready for consumption.

I began to understand why the Duke had been labeled a "poor shipper." It ripens so fast at harvest, and turns so soft, that it would be incredibly difficult to keep these avocados from spoiling in large numbers. Growers would have been required to move boxes of fruit from field to store bins within a day or less. This effort also would have required consumers to snap up all of the fruit before it could spoil. And as I would come to find out, Duke fruit will spoil quickly once it's been harvested. That window of 48-72 hours isn't much.


My First Duke Avocado Harvest
So -- what does a Duke avocado taste like after it's been allowed to ripen? A little bit like heaven, my friend. Just a little bit like heaven. Duke avocados are creamy good -- offering a higher oil content than the Haas avocado -- which is the standard bearer in the commercial avocado market. Duke avocados also have a nutty flavor not found in the Hass and other avocados.

The skin of the Duke avocado is another treat not to be missed. Skins found on commercial avocados are much thicker and do, in fact, taste like the inside of one of my tennis shoes. But that's not the case with the Duke skins. They are fabulous and serve as a wonderful addition to consuming a piece of Duke fruit.

The Duke!
Since we had far more avocados than we knew what to do with, or eat in any one setting, Venus creamed many of them, mixed in some lime juice to keep it from spoiling, and stuck the finished product into a freezer. It will make for a nice guacamole snack during the next Super Bowl, when the 49ers destroy whatever AFC Team is foolish enough to take the field against them.

As far as the final reviews of the avocado snobs who tasted this year's fruit? I must admit -- those reviews are mixed. Nels Christensen and his wife prefer the Bacon avocado variety. Count David Johnson as a fan, as he consumed his Duke avocados with the skin still on. And as for the wife that is Venus?

The wife that is Venus is looking forward to the day when she will be able to harvest the first of many Duke avocados from her own backyard tree. And, my friends, that is really all that counts.


Fred H said...

Your outstanding writing skills are now matched by your exhaustive detective skills, searching out those rare individuals who are true horticultural craftspeople, such as Iran Sam. Of course, your gardening skills will always be suspect!

HelenB said...

It's not just Dukes that aren't edible right off of the tree. The following is from UC Davis:

How can I tell when my avocados are ripe?
Avocados do not "ripen" on the tree, that is, they do not get soft while on the tree. Once you pick an avocado, it takes about 7 to 10 days for it to soften when left at room temperature. You can speed the process up slightly by placing the avocado in a bag with some other ripe fruit (like an apple) or slow the process down by keeping the fruit in the refrigerator.

As far as knowing when it is ready to be picked, it is hard to tell from the outside when an avocado is mature. What the industry does is called a "dry weight" test which gives you an indirect measure of the oil content of the fruit. If the oil content is too low, the fruit is not ripe yet and will shrivel or stay rubbery insted of getting soft. I suggest you pick a couple of fruit and try to ripen them. If the fruit shrivel up or seem rubbery insted of soft, they are not mature yet. Keep picking fruit every few weeks. Note on the calendar when they soften instead of turning rubbery. Also, note the taste of the fruit. The oil content of the fruit usually increases through the season and there will be a certain point when it tastes "just right." That date will usually vary somewhat due to climate conditions... and some years will be better than others. Some varieties can also reach a point where they have too much oil and some will turn rancid (although many types fall from the tree before reaching that point).

Liana Serrano said...

I just got this message last night from a friend of mine who owns an avocado hobby ranch near Santa Cruz. I talked to him about this a couple weeks ago.

"I am currently working with Brokaw Nursery in Ventura, Ca. to supply me with somewhere around forty trees. The clonal rootstock that I was considering was a DUKE 7....originating from, obviously, a Duke 1. It is frost resistant. Unless you are prepared to fabricate a small green house with imported soil, maybe Zutano grafted to a Duke might be a path to follow. One thing to remember, I spent thirteen years feeding, watering, and weeding a few trees, only to end up stumping them because the didn't taste that good...."

Bill Bird said...

Thank you for writing Liana. I appreciate your input. I really do. I don't know if you had the opportunity check the first posting on the Duke, where it explained I am a true avocado tree MASS MURDERER. Most rootstocks used today are either Duke-7's or Topa-Topa. I've learned an awful lot about avocados and the history of the avocado industry during this quest. Perhaps more than I wanted to know. I am unsure of the rootstock I am using for the three successfully grafted trees. I can tell you that seeds were collected from the few avocado trees that have survived and thrived through our freezing winters on the Valley Floor. Were they, in fact, Dukes? Unknown. History of these trees: Unknown. Can they survive sustained freezes in the winter AND blistering, dry heat in the summer? Yes.

If the scions we pulled from the largest of the two Duke trees, which I strongly believe (but cannot prove) was grafted, and the scions result in an exact replica? I will not be disappointed. Duke fruit is pretty darn good, Liana. Feel free to email me though. I'd like to pick the brain of someone with experience at this like yourself.

Liana Serrano said...

Oh, I may have misrepresented myself here. I'm not an expert at any of this. I've been following your blog for a few months, and that's about the extent of my 'expertise'. I saw your first post about the Duke, and thought that it might work for me. (I'm in Tracy, I responded to another post of yours about melons using a different sign in.) What I know about grafting, I've learned from yours and other blogs, and I haven't ever tried it myself. I want to, though. I have a mock pear in the front yard that I want to graft fruit bearing scions to... I digress.
When my friend said he had Duke rootstock, I thought I'd hit on something big, I didn't realize they are common. I wonder if just letting the rootstock grow would have good results?

Lisa Ivey said...

I have several avocado trees and need a Duke. Suggestions?
Skin grafting, how is it done?

Unknown said...
This comment has been removed by the author.
Ben Pierce said...

Can you have Sam write up his skin grafting techique for an article in the CRFG Fruit Gardener? Or at the very least post it here? Thanks. Ben Pierce CRFG
P.S. Enjoy the website very much.

Bill Bird said...

Hi Ben -- and others who have asked. I wasn't all that familiar with grafting when I saw Sam do his work. When I described his work to another CRFG member with more experience than me, he said: "you mean T-grafting?" And that is essentially what it was -- t-grafting. I had never seen this procedure done before when I first visited Sam, and he had so honed his skills that his success rate was close to 95%. You only approach a skill level like this with time and practice. Unfortunately, time also robs people of memories, and that's pretty much the sad story with Sam. I dearly love the man, but he can no longer be trusted to care for young trees because he forgets about them and they don't get any water. It's sad to see what is taking place, but it happens to the best of us. And it's slowly happening to him.

Pamela said...

A million years later... hows bringing back the Duke coming? A long time ago I commented on one of your posts, having tried one thanks to the Farmers Market in Chico.

I must admit horticulture isn't my strong suit, so I don't understand why Duke root-stock or growing from seed doesn't result in Duke avocados. Like every other person in Butte County whose had the pleasure of consuming a perfectly ripe Duke, getting one of those trees on your property becomes an obsession- and unfortunately one that leads to years of disappointment as you realize only a person with grafting skill will have the option!

Bill Bird said...

Hi Pamela!

Not quite a million years! The Duke tree is less than three years old, 20 feet tall, and produced avocados last year for the first time ever. We got a total of six. This year the tree was covered in a massive number of blooms and I keep waiting for Duke Avocados to emerge from those blooms. Haven't noticed anything yet. But it was about this time last year when I noticed the first fruit to appear.

The tree is doing extraordinarly well and is growing faster than any other fruit tree in the Bird Back 40. I have only one citrus tree close to this size -- and that tree is eight years old. It was the first fruit/citrus tree that I planted.

So, yes, the Duke experiment has been well worth it. I'm hoping for a big crop this year. We'll see.

Bill Bird said...

You can't grow most fruits and citrus from seed. Well, you can, but it won't be true to form. It will produce an inferior quality fruit, or so I've learned. Most fruit trees are grafted. Loquats are one example where you don't need to graft. But it's the only example I know of. And, yes, the Duke is still extraordinarily difficult to graft!

Sandra Lewis said...

I've really enjoyed your articles. I, too, have gotten the Duke obsession since my socal sister's huge Hass went down in a wind storm. Luckily I live in Chico. Are you saying here that a seed from a Duke (Chaffin's) won't result in a Duke and I must graft from the Depot tree? I currently have two Duke seedlings in pots that are finally taking off. I thought I would be able to just plant them out as they got a little larger...? But if they won't be Dukes... Suggestions? And is anyone selling young Dukes yet, anywhere th
at you know of?

Bill Bird said...

A Duke seed will not produce a true Duke Avocado. The only way to get a true Duke is to graft cuttings from a true Duke tree and graft it to the root stock.

Bill Bird said...

There is a grower in the Waterford area who has been known to sell Duke trees. He did the grafting for me on my Duke Avocado tree and did a great job. Suggest you join the Northern CA Chapter of the CA Rare Fruit Growers and strike up a conversation with him.

Unknown said...

Four years ago we bought an avocado at a fruit stand near Oroville. The seller said it was locally grown and had an interesting feature, a loose seed. Interesting, so we toothpicked the seed and put it in water. It took such a long time to sprout that we almost threw it out. Patience prevailed and we eventually potted a foot tall little tree. At 18 inches T pinched off the top of the spike and we put the tree on our deck. Next winter we brought the tree back inside. Spring we repotted into the biggest clay pot we could find at Home Depot, 27 inches diameter. That winter I lopped off about 15 inches off the spike so it would fit under the roof overhang next to the house and covered it with a semi opaque fabric. Today Mr Guacamole is over 12 feet tall.

Your writings have convinced me that we have grown a seed from a Chalfin Farms Duke. I don't understand why that makes Mr Guacamole different from a Duke Avocado, but what is it? And more importantly, will it be able to tolerate the coming winter without my having to construct a cover for it? Do I at least have a tree that can survive cold weather?

We live near Penn Valley in the Sierra foothills at about 1300 feet altitude. Our deck is protected from wind and is about 8 feet above grade. We're in an Oak forest plus two pine trees, so Mr Guacamole sees filtered sunlight all day and direct full sun for about 3 hours. Personally, I've never seen temps below 28F on the deck. Longer term residents claim that snow is possible, but a hard freeze is unlikely. Also, what might be the best time of year for pruning?

Thanks for sharing your knowledge.

Robert Buckthal

Ps: Producing avocados to eat has never been our goal, just a nice deck decoration tree.

Bill Bird said...


You've grown yourself some true Duke rootstock, which was used for years because it was so bulletproof to the soil maladies that can strike avocado trees. This is especially true in the colder regions. Our clay muck doesn't drain well, which can be death to avocado rootstocks. But the Duke appears to be bulletproof.

As for what you have grown, it's anyone's guess. It's not a true Duke. There is only way to get a true Duke, and that is to take clippings from a Duke tree and graft it to your rootstock. In other words, a seed will not reproduce true to form. BUT, who knows? You might get something better. Some of the better avocados to grace the market have been "sports" grown from seed.

As for covering it, I never did cover mine. Didn't need it. The tree will survive until the next owner cuts it down. The Bird Back 40 where the tree stands is just a memory for me now. I don't own it anymore.

Best of luck to you,


Green Thing said...

Hello Bill, from here in Sacramento, what would you suggest as the best route to obtain a Duke tree?

Bill Bird said...

You have to make one on your own, unfortunately. The Duke is no longer sold by anyone on a commercial basis. It hasn't been offered by any nursery for decades. Your best bet is to join the California Rare Fruit Growers organization and start asking questions. I no longer own the home where the Duke is planted.

Heather Letourneau said...

Am I the only one who noticed the dates? In April 2016 you were hoping for a big harvest and by November 2016 you are no longer with the property, or the tree(s). Does that mean you don't know how well it fruited? Eat any? I discovered your journey for the Duke earlier tonight and have since been enthralled, needing to see how it turns out despite the fact that it is after midnight where I am. My heart sank at these last comments. Perhaps you have 2 of your 3 grafted trees with you in pots? I loved your detective work and dedication, your love for your lady Venus, and the fact that you renewed an heirloom variety.

Bill Bird said...

Kudos to you, Heather. For you have discovered that 2016 was a rather difficult year for me. While I can confirm the harvest last year was quite large, I did not witness it for myself. All of the fruit went to another avocado grower -- a true avocado fan. He indicated that he harvested three to four dozen fruits. The passage of time can cause a great many life changes. While I will probably never plant a Duke tree again and don't have any in pots now, should you be a fan, I do recommend the experience.

Heather Letourneau said...

I do hope your next adventure is just as meaningful as your last, but a lot more smooth. I'm sorry to hear that you've been troubled. In my short experience on this earth I have noticed that the few years of crap that one gets dealt are there to push and motivate to things one would have never gotten to otherwise. I fell and rolled and stumbled and at the bottom of the pit I found permaculture. I was a typical American slob before that, no way I'd have gotten here on that path. As far as experiencing the Duke, I'm in the south east. Might be hard to get my hands on one, but would love to try planting one here if I ever got the opportunity. I am confused by a nursery selling Duke 7... I googled for more info and was led to your blog. I know Duke 7 is a common rootstock but how does it differ from the Duke? It's not the Duke, or is it? I'm hoping to plant avocado in my Central Savannah River Area (SC) zone 8a garden and just want to make sure I get a variety that can withstand our infrequent but drastic cold snaps of about 16 degrees. And it's gotta "feel right". Well, here's to continuing a life worth writing about. 🍐