Category Archives: Food


The Fourth of July means red, white and blue to celebrate America’s birthday, but with our mild spring and ample rainfall this year it also heralds fig season in south Louisiana. If your experience with figs is limited to Fig Newtons or once upon a time you had fig preserves on toast, I am pausing for a moment of silence for your taste buds. A fresh fig picked and eaten just off the tree is something else altogether.


Fresh figs do not keep for any significant length of time and you’ll be hard-pressed to ever find them in the grocery store. So, if you’d like to try this summer delicacy, make friends with someone that has a fig tree or grow your own (surprisingly easy for anyone in hardiness zones with winters less than 800 chill hours).The most common varieties grown in the south are the Celeste and the Brown Turkey fig (Texas ever-bearing) which produce small brown figs. The LSU AgCenter has introduced several new varieties in recent years including the LSU Purple and LSU Gold, colored according to their namesakes. I have two LSU Gold trees and as far as taste goes, I cannot sing their praises enough. They have a delicate and very sweet taste. It’s what I imagine heaven must taste like. However, in my n = 2 experience these trees get huge in a hurry. It’s great if you’re impatient for your first fig crop, but beware if your backyard space is limiting. Typically it is not necessary to prune fig trees as with other fruit trees, but you may want to rein in an LSU Gold tree in a small backyard. This is less of a problem with Celeste or Brown Turkey figs.

LSU Gold

LSU Gold

If you are new to fig tree culture, you may ask yourself, “I wonder what fig tree blossoms look and smell like? I am sure they must be equally heavenly.” Yes, that’s because the ‘fruit’ you are eating are actually a special type of inflorescence structure (read flower) with the botanical name syconium or synconium. It is basically a modified fleshy stem that encloses numerous ovaries (floral tissue). The inner pulp is the flowers.


You should also beware that fig stems (branches and where the fruit are picked) produce a milky latex material to which some people can be sensitive. It contains the enzyme ficin that will degrade proteins. In fact, this enzyme is used commercially to differentiate blood groups for transfusion purposes. Human blood types go beyond the standard A, B, O or even Rh designations. There are numerous antigens on the surfaces of our blood cells that can affect transfusion success. The Kidd antigen type on your red blood cells and kidneys is difficult to determine in its normal state, but treatment with the enzyme ficin aids in differentiation because the partially degraded product will be more reactive while other variants are resistant to ficin degradation.

Whether or not you care about the finer points of their plant biology or use in biochemical assays, once you have your own fig tree(s), you will inevitably become overwhelmed with the glut of fruit produced in the month of July. You can pawn them off to family, friends, neighbors and acquaintances. Drying them in halves is another great option and intensifies their flavor for use in cooking later. Hardcore enthusiasts will can them as preserves. Now, I was never taught the secret of my grandmother’s fig preserves, but I have read the protocol. Even with a PhD in biochemistry and finely honed protein purification skills at the lab bench, the multi-step process of successfully preparing fig preserves gives me pause. So, who wants figs this Fourth?



References and Links:

Epiphany Hidden in Fava Beans

January 6 is Epiphany, not a week into the new year and its tradition causes many Louisianians to abandon any resolutions related to gustatory moderation. I’m referring, of course, to the King Cake. In modern tradition, a King Cake is a circular pastry made of Danish-type dough, filled with fruit spread, cream cheese, flavored sugar or some combination thereof topped with an additional layer of icing decorated with purple, yellow and green colored sugar. There is a plastic baby, representing Jesus, inside, and the eater finding the slice with Jesus is charged with purchasing the next King Cake. This continues throughout the Carnival season. It truly is the decadence of Mardi Gras captured in cuisine.

King Cake via Wikimedia

Traditionally, the King Cake has slightly more humble origins. It has always been associated with Epiphany, the church holiday marking the visitation of the Three Kings to see the baby Jesus, but the recipe was not always the refined sugar freight train it is today. Think more bread and dried fruit. Before the advent of plastic trinkets, the baby Jesus was symbolized by the fava bean.

Vicia faba via Wikimedia

The fava bean (Vicia faba) or broad bean is a hardy legume that has been in cultivation for thousands of years. This low maintenance crop has been a source of quality protein for the human diet for just as long. Its class connotations have waxed and waned throughout history, but for some people it can trigger a potentially deadly anemia. The condition is so tightly linked to fava beans, it is known as favism.

The king is dead?

Favism is really just one manifestation of a deficiency in the enzyme Glucose-6-Phosphate Dehydrogenase (G6PD). This is the rate-limiting enzyme within the pentose phosphate pathway, which the cell uses to generate reducing power in the form of NADPH and glutathione as well as 5-carbon sugar groups to use as building blocks of DNA or amino acids. People can display a range of G6PD deficiency levels. This depends on the type of mutation and the relative amounts of the mutant G6PD expressed. This mutation is X-linked, which means you inherit it from your mother. Because males inherit only one X chromosome copy, if they get a defective version, they will always display some level of favism. Female carriers of the G6PD mutation can also show some deficiency as well. Even though female carriers contain two X-chromosomes (of which has a normal G6PD and the other has the mutant version), cells only need to use one copy. Relatively early in development, one copy of the X chromosome in each cell is silenced. Thus, there is a random inactivation of one copy of the G6PD gene in each cell; in some cases the mutant version will be inactivated, in others the normal version. This creates the potential for a range of G6PD deficiency to be observed even when the woman has one copy of a normal G6PD.

So how can fava beans wreak such havoc on basic human metabolism? Fava beans synthesize the alkaloid glycoside, vicine. This substance is a particularly powerful trigger for oxidative damage to the cells. In the red blood cells of G6PD deficient individuals, there’s just not enough reducing power within the cell to protect them from the build-up of hydrogen peroxide and other damaging reactive oxygen species. Consequently, the red blood cells burst open resulting in acute anemia.

Vicine chemical structure via Wikimedia

Long live the king!

How have this metabolic mutation and food crop coexisted for so long? It seems like nature and/or agriculture would select for one or the other. There are other beans out there, ‘Am I right?’ And how could a mutation in such a critical enzyme in central metabolism accumulate in more than 400 million people worldwide? The answer lies within another disease- malaria. The incidence of G6PD deficient versions is higher in individuals of African and Mediterranean descent. There is a working hypothesis that some level of G6PD deficiency offers a fitness advantage over normal individuals when it comes to malaria infections. When the Plasmodium parasite infects red blood cells, some amount of oxidative stress occurs. Because G6PD deficient individuals have a sensitivity to this stress, their red blood cells burst eliminating the parasite’s home. When you consider a population of red blood cells within a G6PD deficient individual infected by the parasite, it’s advantageous to be able to sacrifice some red blood cells in order to give the immune system the chance to clear the parasite. In normal individuals, all red blood cells are easy targets for the parasite, which can enter them and hide more effectively from the host’s immune system. It should be noted though that some malarial treatments given to G6PD deficient patients can be toxic themselves as they also generate a fair amount of oxidative stress.

G6PD deficiency is a relatively benign condition when it is diagnosed and certain oxidative triggers are avoided. So in the same way that it’s good to uncover a plastic Jesus in your King Cake, it’s good to know your G6PD variety. If you’re G6PD deficient, it’s not so good to uncover a fava bean. However, the complicated hidden interrelatedness of each of these things will lead to new epiphanies in malarial infections and their treatment.


References and links:

The Twelve Days of Christmas Plants

If you’re looking for a holiday related diversion, here’s a linkfest of my posts from last year on the Twelve Days of Christmas plants. Understand the plant science behind the traditions. Use these random facts to quickly change the subject when nosy but well meaning friends and family ask you uncomfortable questions.

The Twelve Days of Christmas Plants


1. The Christmas Tree

2. Chestnuts

3. Poinsettias

4. Holly

5. Peppermint

6. Mistletoe

7. Grapes

8. Greens and Black-eyed Peas

9. Sugarcane

10. Oranges

11. Pomegranates

12. Boswellia sacra and Commiphora myrrha


If you’re craving even more holiday nerdery or you’ve already used my random facts as diversion tactics last year, check out The 2014 Chemistry Advent Calendar over at the Compound Interest blog. Or check out these Yuletide plants gone global you’ve probably never heard of from the John Innes SVC blog.



Behind the Music: Plants

I’ve spent a lot of time on this blog writing about the importance of plants. They are the energetic foundation of our biosphere. We use them for food, fiber, fuel and building materials. This is why it is so important to understand how they work to further extract useful work and energy out of them. Today’s post explores an area that plants have not been adequately exploited, and I have no idea why we haven’t jumped on this sooner. I’m talking of course about music production.

Before you can even utter LOLWut!?!, allow me to introduce Data Garden. They are a group dedicated to creating new electronic art and have successfully completed a Kickstarter campaign to fund MIDI Sprout. It’s a cool idea with an even cooler logo (also true for Data Garden generally). MIDI Sprout is a device that allows users to create biofeedback art from plants. Huh? You attach the electrodes to the leaves of your houseplant and it records the changes in electrical signals emitted by the plant into an output readable by synthesizers and computers. So, basically it allows you to turn your plant’s existence into music. They’ve already had an exhibit at the Philadelphia Museum of Art and the recording is available for purchase on their website.

So many thoughts on this…

This may blow your mind, but so many of us plant scientists, photosynthesis researchers specifically, have been communicating with our plants using light and fluorescence to determine how healthy or sick they are. We haven’t been listening to them. Maybe I can finally get a Science or Nature paper if my methods include synthesized acoustics as an assay for plant fitness. Those journals just fall all over themselves when it comes to new methods. The evil scientist in me wants to hook up my lab plants to the MIDI Sprout electrodes and run all of my usual experiments and treatments- red light excitation, treatment with the herbicide DCMU, plant hormones, methyl viologen, DBMIB, or high or low CO2 conditions. I would also require an instrument with submersible electrodes so I can record my algal and cyanobacteria cultures as well. Why should plants be the only photosynthetic organisms to hit the top 100?

The MIDI Sprout is advertised as an instrument to listen to your houseplants, but I don’t think my singular Cristmas cactus will cut it. I’m sure it’s just because you need a pluggable power source, but a portable version can probably be developed with enough solid state storage capacity to cache recorded responses until you can get back to the studio and remix everything. Then you can listen to gardens, natural environments, GMO cornfields or whatever you want. Move over Sound Garden, here comes Garden Sound. Interestingly, there are already quite a few musical recordings close to the genre if you search iTunes for ‘photosynthesis.’ They Might Be Giants has a catchy song about photosynthesis on their ‘Here Comes Science’ album. There’s also a group called Carbon Based Life Forms experimenting in the new age genre with plant-related themes. There’s even a group called ‘Plants’ on the new age label Strange Attractors in the same spirit. However, these are all humans as far as I can tell- autotroph imposters or interpreters- and not actual plants.

Plant-based music could introduce entire new genres and bands. What could they be called? Well ‘photosynthesizers’ is a little obvious and hack and I use it for something else. Phonosynthesis is already taken (recommend the album BTW). I’m copyrighting the term ‘autotrophony’ today as this new music genre. I’m sure it will stick if I hashtag it up on the interwebz. Regardless just think of the possibilities… Chard in G minor, Cacti concerto, Solanum sonata, tulip tunes, floral phonics. Autotrophic American Idol. Move over Beyoncé, here comes Botanée. Producers could create the perfect plant boy band equivalent with different potted species with no chance of a break-up. Can’t storm off stage if you’re immobile! If you hated Monsanto as an agribusiness empire, just wait until they break into the music industry. They will surely negotiate for royalties on music made by plants their seeds produced.

I’m thinking we could kick this movement into the mainstream. Some of the plant-synthesized music has some potential. It just needs some help from our species, since we will be the ones purchasing it. Collaborations with existing artists are what we need. Just think- there could be actual black-eyed peas on The Black Eyed Peas album. Remixes are where it’s at, so I just need the Skrillex Ilex, Avicii Vitis or David Guetta Betula remix. I’m thinking clap tracks ala LMFAO and vocals by Pitbull and Ke$ha. There’s gotta be a hit in there somewhere. I really just need to be a one-hit wonder to fund my photosynthesis research for the rest of my career, but short of that I could probably just DJ weddings, parties and bar mitzvahs on the weekends to independently sustain my lab outside of federal funding dollars.

Dr. Z Scheme PhD Sigh, there were no female DJ clip art images.

Dr. Z Scheme PhD
Sigh, there were no female DJ clip art images.

Of course, there are other artistic experimental ventures I could do with this system. I could try something totally meta. Remember that Talk to a Plant museum exhibit aimed at influencing plant growth with sound? What if you played music to plants while you were recording them for their music? Would it sound similar to the music in the room? Would those recordings be different than the music plants make in silence? Yeah. Mind. Blown.

Why does it have to be just an auditory experience? Why can’t you record the music of your food plants then eat them while listening to their music. I’m also trademarking the ‘Salad Soundtrack Bistro.’ If you live in a state like Colorado, recordings could be made of certain plants used for other recreational purposes and they could be sold as a packaged altered experience. Note, it’s just a good business plan to put my Music Munchie Bodega next door.

Clearly, I have tons of creative ideas for future plant exploitation for the sake of the arts and making money. I’m very curious as to the general availability of the MIDI Sprout on the horizon. If any readers have connections in the music industry, tell them to contact me. Otherwise, I guess I will have to figure out how to start my own youtube channel to get noticed. My music mogul persona is Dr. Z-scheme PhD on my P680 Fluorescent label.* Let’s do this.



*My plant science nerd friends reading this will get it.

References and Links:

Blackberries: Jewels of Spring

101016Southern springtime brings many botanical treasures, which are usually proudly displayed in orderly fashion in well-kept garden beds. However, the jewels I cherish most are found along overgrown fence lines and creeping into unkempt pastures. I’m talking about wild blackberries or dewberries or whatever you would like to call species of the Rubus genus. In early spring, X’s can be marked on treasure maps when a profusion of white flowers bloom almost synchronously on two-year old canes. After this display, the plants blend into the background greenery nearly lost and relegated to the shadows of honeysuckle and other trees that finally decide to leaf out. Persistent foragers are rewarded several weeks later when ripening berries can be seen in flashes of red, purple and ultimately black.


Like all precious treasures, blackberries are heavily guarded by barbed brambles. Personally, I’m as at home in a briar patch as Br’er Rabbit and won’t let the snags and sticks of the berry canes keep me from my delicious prize. I’ll endure encounters with bugs of all kinds- mosquitos, fire ants, chiggers, ticks, spiders, and stinging caterpillars. Larger animals will elicit a stronger startle response from me- the flutter of birds, the scurry of rabbits or field mice, the scamper of feral cats and even once the bustle of an extremely near-sighted armadillo. There is only one thing that will cause my stomach to pucker and lead me to call it a day on blackberries- the slither of a snake. This time of year in Louisiana, a snake encounter is a statistical certainty during blackberry picking. Even if I don’t see them, I accept that they are there. I will even go so far as to acknowledge their right to exist in my berry patches.* I would just never like to confront them. So, I tromp heavily in boots and use a cane knife to shake the briars a bit before plunging into them up to my elbows. When I do happen upon the fearsome reptiles, the encounters are never lethal despite my cane knife, but I do lose the nerve for berry-picking for the day.

Blackberry bucket

Blackberry bucket Credit: Johnna Roose

Dewberry canes

Dewberry canes Credit: Johnna Roose

The internet tells me that there are some cultivated varieties without thorns at all that can be grown orderly-like vineyard-style, but it is difficult for this southern girl to reason why you would take the effort to tend such plants when wild varieties produce such deliciousness for free with no aid from a gardener. Nevertheless, several links at the end of this post provide details on blackberry cultivation if you are not a wild-blackberry purist like me. For many wild varieties, some have prominent prickles on the stems and spines on the leaves, while others have additional sharp hairs along their stems. This brings us to an issue of nomenclature dear to some people’s hearts. (No, I’m not talking about thorns vs. prickles vs. spines. I’ve covered that previously.) I’m talking about blackberries vs. dewberries. While blackberries may be an umbrella term for this type of fruit, I’ve noticed that southerners prefer to make the distinction when dewberries are what you are really talking about. I am an equal opportunity berry picker and eater, but here are the highlights when it comes to dewberries. Dewberries, Rubus trivialis**, are slightly larger than most wild blackberries and ripen a few weeks earlier. Their canes are red and contain hairy bristles in addition to prickles, while blackberry canes are green and lack the extra layer of hairy bristles. Blackberry plants have a more upright form, while the dewberry canes bend and creep along the ground with tips that root easily to conquer more ground.

Blackberry, an aggregate fruit of drupelets. Credit: Johnna Roose

Blackberry, an aggregate fruit of drupelets.
Credit: Johnna Roose

While we’re on the subject of nomenclature, there’s something more fundamental we need to talk about. //looks over both shoulders and whispers// They aren’t really berries, botanically speaking. Yes, it’s true. This is another instance when common or culinary usage of a term differs from the strict scientific definition. In the world of plant science, a simple berry is a fruit containing the seeds and pulp from a single ovary. So, things like blueberries and cranberries are examples of fruit both commonly and scientifically referred to as berries. Other believable berries include grapes and currants. You may not believe me, but based on the botanical definition avocados, tomatoes and watermelons are also berries. Incidentally, strawberries are not berries either, but that is a subject for another post. Blackberries, dewberries and raspberries are aggregate fruit, in which each tiny round fleshy piece (a drupelet) is derived from a separate ovary in the flower but bound together in the form we commonly refer to as a berry. Don’t worry, I’ll still call them blackberries because blackaggregatefruit just doesn’t have the same ring to it.

After all, when it comes to food plants, being scientifically accurate takes a backseat to culinary use. ‘Berry cobbler’ just triggers a Pavlovian salivation response that ‘Aggregate fruit cobbler’ doesn’t. I know this isn’t really a food blog, but I feel strongly about wild blackberries, and it’s my blog and I can do what I want. Blackberries should be eaten out of hand using sunshine and dew as the only condiments. If there are any surplus berries, then you should bake them into a cobbler, tart or pie. There are many pastry recipes with berry ingredients, and I’m sure many are delicious. However, I am a minimalist. I rely on the berry cobbler recipe from the ‘Quick-N-Easy’ section of the 1981 Istrouma Baptist Church cookbook. Ingredients: 1 stick of salted butter, 1 cup of flour, 1 cup of sugar, 1 cup of milk and 2 cups of berries. Melt butter in baking dish. Mix other ingredients (except berries) together in bowl and pour over melted butter in baking dish. Pour berries over entire mixture and bake at 400 F until golden brown. It’s not fancy, but the simple gooey batter is the perfect medium for the tart flavorful berries. If you’ve really gotten more berries than you can handle in a single dessert preparation, then cook them for juice to make into jelly. Check out this resource from the LSU AgCenter for more information and recipes.


Blackberry cobbler and vanilla ice cream Credit: Johnna Roose

Blackberry cobbler and vanilla ice cream
Credit: Johnna Roose

The good thing about this treasure is that there is plenty to go around for all determined prospectors. Grab your boots and bucket. It’s berry pickin’ time (or soon will be for those of you just a bit further north).




*My brother would disagree with me. He is convinced that all snakes are copper-headed rattle moccasins. It’s either kill or be killed, and he will put down a layer of cover fire from his handy sidearm at the first sound of scales.

**trivialis, as in trivial. Really, botanical nomenclature, really? I find it hard to believe that anyone that has tasted dewberries would have called them trivial in terms of flavor. They probably should have been named Rubus heavenlyflavorexplosiononmypalate.

References and links:

So, this link provides an unbelievably detailed 15-step protocol (15!) for blackberry picking.

Here’s my version:

  1. Put on boots.
  2. Grab cane knife and bucket with handle.
  3. Tromp to back pasture and walk along fence line.
  4. After unripe red berries catch your eye, look for fully ripe blackberries nearby. For every ripe blackberry in the sun, there’s five more hiding under the shade of the leaves.
  5. Be careful not to step on ant piles, field mice, or snakes.
  6. Curse birds and small mammals that scurry out of the berry patch as you approach.
  7. Pick ripe blackberries and eat one for every five you toss in your bucket.
  8. Use yoga breathing techniques, balance and poses to reach ripe berries deeper in the patch.
  9. Curse the perfectly ripe succulent berries that fall from your grip into the dark depths of the ground below the briar patch.
  10. Curse the thorns, prickles and spines of the brambles as they get caught in your clothing, hair and flesh.
  11. Enjoy the morning sunshine until you remember you didn’t put any sunscreen on your neck.
  12. Curse because you forgot to put on insect repellent.
  13. See two inches of what must be a six-foot-long venomous snake. Shriek curses and defy gravity to escape blackberry patch.
  14. Upon entering a human dwelling, pick the ticks off of yourself. (Ironically, this step is unnecessary for any canine companions that have been adequately treated with flea and tick preventatives.)
  15. Cook and eat blackberry cobbler, served with vanilla ice cream.

May Bouquet: Hibiscus

April showers have brought May flowers… to the blog. Today’s post is part of a May Bouquet series focused on flowers one might find in a bouquet. Y’know, leading up to Mother’s Day this Sunday. Think of these posts as daily reminders with wonderful suggestions on ways to honor the mothers in your lives.

Pink Hibiscus Credit: Johnna Roose

Pink Hibiscus
Credit: Johnna Roose

Today’s featured flower is the hibiscus. These large and colorful blooms demand notice and are the opposite botanical personality of the shrinking violet. They are synonymous with the tropics, prominently featured on Hawaiian print fabrics, more so than even palm trees and pineapples. In fact, a yellow hibiscus native to the islands (Hibiscus brackenridgei) is the official state flower of Hawaii. Hibiscus plants make great additions to any garden, but if you plan to keep them for multiple growing seasons, they are easier to manage as potted plants. This is because they are sensitive to cold and will have to be protected in most climates during the winter.

Yellow Hibiscus Credit: Johnna Roose

Yellow Hibiscus
Credit: Johnna Roose

Yellow Hibiscus Credit: Johnna Roose

Yellow Hibiscus
Credit: Johnna Roose

If you are looking for a plant to turn any area into a tropical oasis, hibiscus is the right choice. They are available in all types of bold colors- yellow, pink, red, and coral. Hibiscus breeders and hybridizers have been busy generating new varieties in all shapes, sizes and color combinations. There are a large number of distinct species of Hibiscus, but the majority of the ornamental varieties found in garden centers are likely to be Hibiscus rosa-sinensis. Genetically, it is a polyploid. This means it has multiple copies (>2) of genomes and not just the single copy from each parent (diploid) like we are. This wealth of genetic material means that these plants have a seemingly bottomless bag out of which to pull tricks when it comes to flower form and color. Crosses and hybrids of plants can yield all kinds of color combinations; thus, when grown from seed, you never know what you’ll get. If you like surprises, that’s great. If you had your heart set on a particular color, then go with a grafted plant that has been propagated to give the type you would like. Check out some of the links below for more hibiscus flower eye candy.

Red Hibiscus Bloom Credit: Monica Russell

Red Hibiscus Bloom
Credit: Monica Russell

Can’t pick just one favorite color or combination? You may not have to. Some plants have several different varieties grafted onto main rootstock bases to give you a single plant with red blooms on one stem, yellow on another and coral on yet another.

Multicolored Hibiscus Credit: Monica Russell

Multicolored Hibiscus
Credit: Monica Russell

Don’t these flowers just look good enough to eat? Well, you can. The flowers are used as the base for hibiscus tea and dried flowers are also candied and used as garnishes. Humans aren’t the only species that appreciate the taste of the hibiscus. These plants are also attractants for butterflies and birds. If your landscape is frequented by deer, prepare to go to battle to protect your beautiful and tasty blooms from them as well.

Pink Hibiscus Credit: Johnna Roose

Pink Hibiscus
Credit: Johnna Roose

If you’re inspired to grow your own, check your local garden centers now. For my Baton Rouge area friends, we’ve apparently just missed (May 4th) the Red Stick Hibiscus Society’s show and sale, but the shows of the New Orleans and Acadiana Chapters are still to come this month. Or if you are really serious about hibiscus, you may just want to join the American Hibiscus Society. FYI, their national convention will be held in Lafayette, LA in June of this year. Check here for details.



References and Links:


Cinco de Mayo: Avocados

This post will take a break from the May Bouquet series to highlight another holiday- Cinco de Mayo (the 5th of May). In America, this usually means two for one margaritas and supper that features things like tacos and guacamole. In Mexican history, it celebrates the Battle of Puebla, an unlikely victory for the Mexican army over the French in 1862. On a plant science blog, Cinco de Mayo means highlighting a tree that had just about the same odds of surviving as the Mexican army did. I’m talking about the Hass avocado.

Hass avocados Copyright Courtesy of the Hass Avocado Board

Before I recount the unlikely beginnings of the world’s most common avocado variety, let’s consider the avocado as a plant and not just the green mushy base of your guacamole. Avocados are native to Mexico and Central America, and Mexico is the world leader in avocado production. The trees grow to more than 60 feet tall and prefer tropical and subtropical climates. Avocados are climacteric (plant biology word of the day) meaning the fruit will mature on the tree, but it doesn’t ripen. This means that avocados will remain hard as rocks on the tree until eventually they just fall off.* This trait is somewhat useful for the produce industry because leaving the fruit on the tree until demand increases is a convenient and profitable strategy. For example, you may not want to harvest as many of your avocados in March, but a lot more leading up to May when people want guacamole for Cinco de Mayo.

Ethylene via Wikipedia

So, how does the fruit ripen off the tree? The mature avocados will ripen off the tree in about two weeks at room temperature. If there are bananas or apples nearby the process can be even faster. This is because these fruits produce ethylene gas, a plant hormone, which among other things stimulates fruit ripening. Commercial produce distributors also take advantage of these properties and treat unripe fruits with ethylene gas in special rooms to control the timing of ripening. This takes a lot of the guesswork out of the timelines for getting ripe avocados to your supermarket.

For those of you fond of science experiments in the kitchen, one fun activity is sprouting the large seed inside the avocados you eat. You can stick four toothpicks around the middle of an avocado seed and submerge the root end in water. Then you wait. Within a month or two it will produce roots then split and sprout. Of course, you will have to wait another 4 – 6 years before it will produce any fruit.

A picture of a avocado seed, punctured with 4 toothpicks and hung halfway inside a glass with water, so that germination would start. Credit: KVDP via Wikipedia

The Hass avocado variety began as such a sprouted seedling, the result of a cross or trial from A. R. Rideout. It was purchased by Rudolph Hass as an addition to his new avocado orchard in California. Hass intended to use it as rootstock for grafting a scion of Fuerte, the standard variety at the time. The history tells that Hass tried grafting to that stock three separate times, but nothing ever took to it. Such recalcitrance even wore down the patience of an orchardist, and Hass was ready to chop it down. His children convinced him to just let it grow.** They actually preferred the taste of the avocados it produced and it bore well. Hass patented the tree in 1935, naming the variety after himself, and in an agreement with H.H. Brokaw, produced the initial grafts of Hass seedlings. It took some time to change the minds of consumers because the Hass avocado has such dark and bumpy skin compared to the smoother green Fuerte variety. However, the proof is in the taste and the Hass is the winner with a richer, nuttier flavor. Today the Hass variety accounts for the overwhelming majority of the avocado market in the United States (80 – 95% depending on the sources listed below) with more than $1 billion per year in revenues for U.S. agriculture. Sadly, the original Hass mother tree succumbed to root rot in 2002, but the popularity of its avocados with consumers has ensured its genes will live on for many generations to come.

Guacamole Copyright Courtesy of the Hass Avocado Board

As you’re enjoying avocados or guacamole today to celebrate an unlikely victory for Mexico, remember the unlikely biological victory of the Hass avocado. Use this knowledge to impress your friends. After a couple of margaritas, you’ll sound like a genius.



*Useful FYI for any of you out there that may have an avocado tree in your yard and may be cursing your tree as to why it doesn’t produce anything like you see in the produce section of your grocery store.

**Yeah, it’s kinda a theme of mine to take every opportunity to reference the Lorax on this blog.

References and Links: