The Chestnut Song

“The Christmas Song” tops the charts every December, but there’s lots more to know about those chestnuts roasting on an open fire. We peel back the layers in this essay, which is one of our two contributions to this year’s Advent Botany holiday collection.

I first tried chestnuts when I was a student in Paris. The holiday season was peaceful that year, as it should be, and I’ve cherished my memories of it all the more as intense protests are spreading through France, and violence has shattered a Christmas market in Strasbourg. In that long-ago December, though, my most consuming emotion was a kind of double nostalgia. I missed home, and yet I wasn’t quite ready to leave that beautiful city behind. As I walked for hours and hours gathering last looks, it was thrilling to get caught up in the sudden early darkness of winter and the elaborate holiday windows of the grand old department stores. During one evening promenade, I saw a street merchant who had anchored himself in the middle of the streaming agitated crowd and was patiently tending a pan of marrons grillés, freshly roasted chestnuts. The scene was so sepia toned, so achingly 19th century, that I had to have some, just to glut my sentimentality. I bought a newspaper cone of the hot aromatic nuts and managed to peel one with my cold fingers right there on the sidewalk.

Le marchand de marrons

Le marchand de marrons L’Illustration européenne 1881 Jean Jules Geoffroy

The sweet chestnut of Europe is a true chestnut (Castanea sativa), not the beautiful but toxic horse chestnut (Aesculus hippocastanum), which so famously covers Paris with its pink-eyed blossoms in April. They are not very close relatives, as the last common ancestor of sweet Castanea (Fagaceae) and showy Aesculus (Sapindaceae) is estimated to have lived about 100 million years ago. I have happily returned to Paris many times in the summer and fallen in love with its horse chestnut trees. In that frozen moment in December, however, the spell of Christmastime in the City of Lights was broken for me when I realized that I could live happily without any more true Castanea chestnuts.

Chestnuts do not have the cultural meaning in the US that they have in France, where a chestnut roasting pan used to be considered essential kitchen equipment. Fagaceae: Chestnut roasting pan from French cookbookMy theory is that most Americans’ impressions of chestnuts are driven entirely by “The Christmas Song.” Can’t you just smell them roasting on an open fire? And Nat King Cole’s voice – a little sweet, a little smoky – tempts you to linger and savor the simple pleasures of the season. We all want to believe that chestnuts taste like that, but in reality very few Americans eat them. Although sweet chestnuts are grown commercially all across the country, from Michigan to Florida and Virginia to California, the US contributes less than 1% of global productivity (Agricultural Marketing Resource Center), and we don’t import many either.

Reliving the past

This year I found fresh local chestnuts at my neighborhood farmers market, and I decided to give them another try in my own kitchen. Their texture isn’t crispy and fatty like you’d expect from a nut. It is starchy, thick, and dry, like a potato left in the oven too long. But their flavor is very distinct and complex, and now that I’m older and have more realistic expectations, I like them. They are a bit sweet – a cross between a new potato and a parsnip – and a bit savory, with a good dose of umami flavor. They also taste a little woodsy or wild to me. No wonder they are often featured in sweet-savory dishes such as butternut squash soup or pork with a fruit reduction. Roasting brings out subtle buttery or caramel notes, although I didn’t detect those in steamed chestnuts. Monet reportedly preferred them steamed (Joyes 1990), and perhaps he topped them with a bit of country butter.

Whatever you think of their taste and texture, these ordinary looking nuts are interesting to look at and tear apart, which makes the difficult task of peeling them a little more engaging. If you can find whole chestnuts at your local store or orchard, you’ll be able to identify some flower parts and see evidence that each one grew up as a triplet.

Triplettes snug in their beds

Chestnuts are botanically nuts: they have a single seed inside a dry fruit wall that doesn’t open. Each nut comes from a separate flower, but those flowers develop in sets of three, snuggled up in a line inside a very spiny shared cupule. Cupules are familiar to most of us as the cap on an acorn. Chestnuts and oaks are in the same family (Fagaceae) and share this feature of their fruits, but unlike chestnuts, oaks develop only a single nut per cupule. The closely related beeches develop two nuts in their cupules.

Vivario châtaignes

Three sweet chestnut fruits tucked into their spiny cupule. Image: Pierre Bona CC BY-SA 3.0 Wikimedia Commons

Chestnuts are separated from their cupules during harvest, but in your kitchen, you can deduce whether a given chestnut was in the middle or on the end of its row of siblings. End nuts have one flat face and a broad rounded side, where as middle nuts have two flat faces and a narrow rounded side. The pale rough patch on the bottom of a chestnut is where it was attached to the cupule.

Fagaceae: Castanea sativa triplet

A triplet of chestnuts, as they might have sat in a cupule. Note the more triangular shape of the nut in the middle.

Plant morphologists debated the origin of cupules for a long time. The consensus now seems to be that the nuts and their cupules represent a highly modified and complex flowering side branch at the base of an otherwise pollen-bearing (“male”) inflorescence (Fey & Endress 1993; Manos et al. 2001). At the tip of each of these pistillate (“female” nut-bearing) inflorescence branches, the central flower along with its two adjacent flowers develop and become chestnuts while the would-be flowers below them instead come together to become the cupule. The spines or scales evident on cupules are modified branches of that flowering axis.Fagaceae: Castanea sativa whole chestnut

Fresh chestnuts will often still have flowers attached to their fuzzy pointed tips, and it’s probably worth looking for these as a sign of gentle handling since harvest. Female chestnut flowers are very small, but they have relatively long styles that flare above the cupule and catch pollen.

The meat of the nut

Normally, you would cook chestnuts before peeling them, but it’s easier to see their structure if you peel one raw. Start by placing the nut on a cutting board and pressing down on it with the flat of a wide bladed knife to loosen things up. Then carve an X through the side of the nut, cutting deeply enough to catch the seed inside. The shell of the nut (the fruit wall) will be thin and flexible enough to pull away with the tip of a smaller knife or your fingers. Notice that the inside of the fruit wall is covered in soft beige fur.Fagaceae: Castanea sativa peeled

Removing the reddish-brown seed coat from the pale seed inside can be difficult. Sometimes it pulls away easily but often you have to carve off some tenacious spots. Chestnut fans claim that the seed coat is easiest to remove when the nut is cooked and still hot, but all recipes admit that, even so, you must be patient. It’s time to put on some Nat King Cole and sit by the fire.

Fortunately, for our kitchen botany lab, you don’t need to remove the seed coat entirely. The raw partially naked chestnut can be split into two halves, which are large fleshy slightly wrinkled cotyledons. Fagaceae: Castanea sativa embryoCotyledons store resources that a seedling uses to fuel its initial growth. The main axis of the seedling lies between these halves at the pointed end of the nut. When a chestnut seed germinates, a root and a shoot develop from that axis and emerge from the seed, while the cotyledons stay behind, underground, supporting the young seedling.

Roasting the chestnuts

Whether you roast or steam your chestnuts, first score them with a knife as described above, making sure to cut through the seed coat as well. Doing so gives you an essential head start on peeling, and it keeps the nuts from exploding in the fire or oven. Street vendors often make a single deep slash across the chestnut, but I like to carve an X because it makes a prettier roasted nut. The shell around the crossed cuts curls back on itself and reveals the pale fuzz inside, like the lambswool lapels of a leather jacket. The look is less Belle Époque Paris and more American western, like something you would wear when you saddled up a horse to ride into the mountains and chop down a rustic Christmas tree.

Fagaceae: Castanea sativa roasted chestnuts

Roasted chestnuts in leather jackets

Once you have cut all the chestnuts and put the knife safely away, you can open the wine. Many sources recommend pairing roasted chestnuts with a young, slightly sparkling red wine to cut through the dense dry mouthfeel of the chestnuts. A smooth seasonal beer is nice, and I imagine hard cider would be too. Whatever you choose, I hope that the sparkles in your glass bring to mind the twinkling stars and holiday lights of a peaceful season around the world.

References

Agricultural Marketing Resource Center https://www.agmrc.org/commodities-products/nuts/chestnuts

Angiosperm Phylogeny Website http://www.mobot.org/MOBOT/research/APweb/orders/zygophyllalesweb.htm#EurosidI

Fey, B. S., & Endress, P. K. (1983). Development and morphological interpretation of the cupule in Fagaceae. Flora, 173(5-6), 451-468.

Joyes, C. (1990) Monet’s Table: The Cooking Journals of Claude Monet. New York, NY:Simon & Schuster

Manos, P. S., Zhou, Z. K., & Cannon, C. H. (2001). Systematics of Fagaceae: phylogenetic tests of reproductive trait evolution. International Journal of Plant Sciences, 162(6), 1361-1379.

Angelica: Holiday fruitcake from a sometimes toxic family

Angelica archangelica may be the most festive species in a crowded field of charismatic relatives. Just watch out for the toxic branches of the Apiaceae family tree. This essay is one of our two contributions to this year’s Advent Botany holiday essay collection.

For scientific names of plants associated with the winter holidays, I think it would be hard to beat Angelica archangelica. Commonly known just as angelica or garden angelica, A. archangelica is one of the few cultivated members among the 60-ish species of large biennial herbs in the genus. They are distributed primarily across the northern reaches of Europe, Asia, and western North America.

Angelica stalks candied and photographed by hunter-harvester-gardener Hank Shaw. Recipe on his blog

Candied angelica stalks (young stems and petioles from first-year plants) have long been prized in Western Europe as a unique confection or addition to baked goods. If your path this holiday crosses with a fruitcake studded with bright green chunks, those are unfortunately dyed pieces of candied angelica stalk. Or you may have a qualitatively different experience with angelica in the form of delicious liqueurs that include the root or fruit of the plant as an ingredient. The floral, spicy, and fresh flavor of angelica graces gins, vermouths, absinthes, aquavits, bitters, and Chartreuse, among others (Amy Stewart’s website accompaniment to her book The Drunken Botanist has some tips for growing and using angelica for the DIY mixologist). Continue reading

The Ballad of Farro Salad

We botanists in the kitchen are busy preparing for Thanksgiving, as you probably are too. Please enjoy this quick song about a grain salad. And if you still need ideas for vegetarian side, consider this a recipe.

To the tune of Darcy Farrow.  (See this version by John Denver if you don’t know the tune.)

The Ballad of Farro Salad

Where the water runs down to the Nile River plain,
There came a kernel, emmer farro was its name.
A wheat of four-fold ploidy, and a fair one to see,
The sweetest texture e’er found in a grain.

It goes well with tomatoes, cherries red and gold.
The larger ones we halve; the littlest we leave whole.
Add goat cheese crumbled in, with parsley julienned.
Serve at room temp or maybe even cold.

Oh they sing of emmer farro where the Hudson runs through.
They sing of its beauty out in San Francisco too.
At dusky sundown, to its name they drink a round,
and to its golden hearty chew.

Botany lab/rant of the month: that’s a magic beanstalk, not a soybean

In chaotic times, there are moments when you just have to take comfort in order anywhere you can find it. Katherine reviews some basic plant growth rules and takes a major company to task for undermining botanical literacy.

Would you buy milk from a dairy whose smiling cow mascot had an udder perched on top of her head? Would it bother you to see waiving teats where her ears should be? What if the unsettling image were wrapped in a lyrical ode to ungulates and to the steadfast farmers who rise before dawn to tap into “all that mammalian goodness”? Would a Holstein hagiography be enough to distract you, or would the contrast between carefully crafted ad copy and a negligent disregard for bovine biology trip your bullshit meter?

I think about this every time I buy soy milk made by one particular giant of the non-dairy milk industry. Normally I make my own soy milk – it’s cheap and fast and delicious – but sometimes life intervenes and I have to go with convenience. At my favorite local grocer, that means buying this brand. You might think it’s the gellan gum and the “natural flavors” that offend me, but really I just can’t get over the carton.

Have you ever really thought about the magic of plants?” the carton beckons. Well, yes! Yes I have! Like me, these producers have “been rooted in plant power for over 20 years.” Wow, we have so much in common! I am invited to enjoy “all that leafy goodness” and call them “plant-based, plant biased or just plain plant-prejudiced.” No plant blindness here, right? 

Except for this, the botanical version of a cow with an udder on her head and a tail growing out of her chin:

Someone's wildly inaccuarate idea of a soybean plant. the brand name has been obscured to protect its reputation.

Someone’s wildly inaccurate idea of a soybean plant. The brand name has been obscured to protect its reputation. Click to enlarge.

Judging by the edamame pod randomly stuck onto a stem, this altered photo is supposed to represent a soy bean plant (Glycine max). The words below (“Discover the power of plants at [redacted].com”) almost promise botanical accuracy. Yet, for comparison, here is an actual soybean plant, with its trifoliate leaves and bushy growth habit:

Soybeans in Warren County, Indiana

A soybean plant growing in Indiana.

Not only is the image on the soy milk carton clearly not a soybean plant, but the chimeric little sprout violates basic patterns of plant construction. When I showed the carton to my class this spring, the students were all over it with fervor and a sharpie.

Why it matters

There are many extremely important and urgent challenges facing humans and other organisms all over the planet right now, including some negative social and ecological impacts of soy and the potential for new tariffs on U.S. soybeans to make these worse. So why direct righteous ire against the photo on a carton of soy milk? First of all, what biology teacher (or parent or anyone) wants to see inaccurate or misleading images, especially if they appear every single morning on breakfast tables across the country? Second, at the risk of overstating my case, I believe that someone made deliberate choices about both the text and the image on this carton in order to evoke health and sustainability, but that these choices actually expose indifference toward the plants, the farmers, and the natural world. Similar indifference has gotten our species into a lot of trouble. We all get things wrong, but it’s important to try not to.

How a plant body is supposed to look

The green world is full of gigantic trees and tiny floating plants and delicate vines and cacti and orchids and palms and titan arums. Even if we leave aside mosses and ferns to focus on seed plants, it’s obvious that natural selection has taken a very simple basic developmental program and pushed it in almost every conceivable morphological direction. A common set of plant growth rules accommodates the varied forms of a quarter million or more species – which is astonishing – and yet the graphic designer for this soy beverage company somehow managed to stitch together an oddly improbable plant.

Under the basic developmental program, the set of stem cells (the meristem) at the apex of a growing shoot spins off a series of appendages (e.g. leaves) at regular intervals, arranged along the stem in a regular pattern. Most often, appendages spiral around the stem or occur in opposite pairs. The resulting basic vegetative unit is a leaf (or leaf homolog such as a bract, scale, or spine), the span of stem below it (the internode), and a bud at the place where the leaf meets the stem (the axil). A shoot grows by adding these units in sequence. New leaves continue to expand and internodes continue to elongate for a little while, so leaves near the tip of a shoot tend to be smaller and closer together than they eventually will be. Buds in the axils of the appendages may themselves grow out as branches that reiterate the basic body plan. The result is a modular and potentially nested structure composed of repeated subunits.

Basic flowering plant body plan

Flowering plants (and other seed plants) are built from a series of basic vegetative units, consisting of a leaf and an associated axillary bud and the internode below it. Axillary buds may develop into branches that are similarly built of a series of vegetative units. When plants begin to flower, bracts often develop in place of leaves, and flowers emerge from buds in their axils. Note that this generic plant is not meant to represent any particular species.

When a plant starts to flower, this regular organization does not go away, even if it is modified somewhat. For example, flower clusters (inflorescences) are generally produced at branch tips and along shoot axes where leafy branches would have emerged. And while leafy branches are associated with (subtended by) leaves, inflorescences are subtended by leaf-like appendages called bracts. Inflorescences themselves might transition to a complex branching architecture that differs from the rest of the vegetative plant body, but they still produce flowers in a regular pattern. Because individual flowers are conceptually (and evolutionarily) a bit like branches, they also are usually associated with bracts (Rudall & Bateman, 2010). A notable exception is plants in the mustard family (Brassicaceae); one of the genes that tells a meristem to switch gears and make a flower also suppresses formation of a subtending bract (see summary in Krizek, 2009).

Practically, what this means is that any branch, flower, or inflorescence should be associated with a subtending leaf (or bract, scale, or spine) and that any leaf (or bract, scale, or spine) potentially has a bud, branch, inflorescence, or flower associated with it. The regularity and simplicity of this fundamental pattern of seed plant development gives you a powerful framework for interpreting plants. You no longer have to ask what kohlrabi is; the leaf arrangement gives it away. You can use a combination of clues to distinguish a single compound leaf from a branch. It’s fun.

True, the pattern is not always obvious. Leaves and bracts fall off (although they often leave evident scars), and axillary buds can be extremely small or obscured. Leaves can also be reduced to tiny scales, such as those on a potato tuber. Flowers and fruits of the chocolate tree (Theobroma cacao) appear to emerge directly from an old branch, but in fact they are associated with long-gone leaf axils. And woody plants can produce new shoots adventitiously at their bases or when they are damaged. But we were talking about soybeans, not redwoods.

A magic beanstalk

Returning to the image that set off this screed, I might be able to see it as a harmless, fanciful botanical embellishment if it weren’t for the soybean pod deliberately pasted onto the stem. Surely these plant-prejudiced people could have paused their musings on the magic of plants and simply observed an actual soybean plant. They might have noticed that soybeans have compound leaves with three leaflets and that they grow more like bushes than vines. With a good photo, the artist could have gotten this image right without knowing anything at all about how plants develop. However, the text strongly implies that the central values of the company are rooted in a genuine understanding of plant biology, so I think it’s fair to hold them to a higher standard.

Now that I’ve said my piece, it’s time to take a virtual sharpie to that carton and make it botanically correct. Here’s my version.

Making soy milk at home

Homemade soy milk has many advantages. The beans for a half gallon of soy milk cost about a quarter of what you would pay for a carton at a store. Making your own is also more sustainable: bulk dried beans are less resource-intensive to ship than packaged liquid, you can often choose the source of your beans and how they are grown (e.g. organic from the U.S.), and you can control waste from the process. For example, I mix the solids strained from the liquid milk with salt, nutritional yeast, and whatever spices are handy and pack them for lunch. To the milk, I can add vanilla or not as I like. I can throw some oats or nuts or soy lecithin into the boil if I like.

  • 1 cup dried soybeans
  • water for soaking
  • 8 cups of water
  • dash of salt
  • 1/4 cup of rolled or steel-cut oats or almonds or cashews
  • immersion blender
  • fine strainer or cloth strainer bag

Soak soybeans in a medium saucepan (1.5 qt) for at least 6 hours. If you are using steel-cut oats, almonds, or cashews, soak them too.

Bring 8 cups of water to the boil in a large stock pot. The larger the better to reduce the chance that the mixture will boil over.

Drain and rinse the soybeans and return them to the sauce pan. If you are using rolled oats, add them here.

Pour some of the boiling water over the beans to cover them by about an inch, and immediately puree them with the immersion blender. Using boiling water denatures some enzymes that can cause off flavors, and an immersion blender is much safer than a regular blender for hot liquids.

Pour the blended beans into the large stock pot with the rest of the boiling water. Turn the heat to the lowest setting possible. After about 5 or 10 mins, put a lid on the pot and let it cook for another 45 mins. Add a dash of salt about midway through.

Do not leave the pot alone until it has been simmering without trouble for a while. The mixture has a tendency to boil over and make a huge mess within the first 5-10 mins.

Allow the mixture to cool for an hour or so and strain it. Refrigerate the milk right away.

The remaining solids can be flavored and eaten as they are, stirred into breakfast oatmeal or grits, baked into muffins, etc.

References

Krizek, B. A. (2009). Arabidopsis: flower development and patterning. eLS, 1-11.

Rudall, P. J., & Bateman, R. M. (2010). Defining the limits of flowers: the challenge of distinguishing between the evolutionary products of simple versus compound strobili. Philosophical Transactions of the Royal Society of London B: Biological Sciences, 365(1539), 397-409.

Spruce tips

It’s nearing the end of the spring spruce tip season here in southcentral Alaska.

chopped spruce tips

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Kiwifruit 2: Why are they green?

Why are some kiwifruits green when they are ripe? Or avocados or honeydew melons? The answer involves genetic accidents, photosynthesis, hidden pigments, and the words “monkey peach.”

In our kiwifruit fuzziness essay we described how the type and density of trichomes—the hairlike projections from the fruit’s skin that create the fuzziness—in the Actinidia chinensis species complex is correlated with the habitat in China to which a particular population is adapted and the ploidy level of its genome. Only polyploid (having multiple genome copies) Actinidia chinensis occupy the harshest environments—the high, arid reaches of western China—and have the highest trichome density and the longest trichomes. And those fuzzy, resilient, polyploid kiwifruits are all green on the inside (1). They are the plant kingdom’s version of an unshaved vegan after backcountry skiing for a week. The hardy plant had no trouble growing outside its plateau of origin and became the most common commercial kiwifruit in the world (A. chinensis var. deliciosa), followed closely by yellow-fleshed (“golden”), less fuzzy variants of the same species (A. chinensis var. chinensis).

An expanded view of the dozens of Actinidia species reveals orange, red, and purplish pigments that color fruits in the genus. While beautiful, this warm palette strikes me as noteworthy only in contrast to the bright green displayed by the fuzzy A. chinensis var. deliciosa that initially grabbed my attention, and, later, in green kiwiberries (A. arguta). A non-green (for lack of better terminology, “colorful”) ripe fruit, after all, is a common end point for species with fleshy fruit.

Fig. 1 from Crowhurst et al. (2008) of some fruit diversity in the kiwifruit genus Actinidia. We describe the botany and anatomy of kiwifruits in our kiwifruit fuzziness essay.

It is not difficult, however, to bring to mind other examples of species with green-ripe fruit: avocado, green grapes, some citrus, honeydew melon (I’m specifically thinking here of the pericarp or mesocarp tissue under the skin and exclude from this discussion immature fruits that lose their greenness when fully ripe, like green beans and olives). Green ripe fruit, then, in Actinidia and other taxa, seems to me to be something to explain. What, if any, function might it serve, and what are the mechanisms responsible?

While the literature on the subject is far from exhaustive, there is a fairly pedestrian explanation at least for the mechanism, if not any adaptive function, of unusually green fruit flesh outside of Actinidia: fruits start green, and straightforward mutations in a few key genes cause them to remain so. Like that intrepid, hirsute montane vegan, though, Actinidia performs the task a little differently, and it is a bit of a mystery. To understand why that is, we need some backstory on pigments in fruit and how and why they change as fruit ripens, with a focus on Actinidia. Continue reading

Kiwifruit 1: Why are they so fuzzy?

Kiwifruit is not covered in hairs. It’s covered in trichomes. And only if you’re talking about green Actinidia chinensis var. deliciosa. But, why? One answer is: pretty much to keep it from drying out. Another is: because it’s a polyploid from western China and was kind of chosen at random to be the most commonly grown kiwifruit, and they’re not all fuzzy. Those aren’t mutually exclusive answers. Put on your ecophysiology hats and grab a paring knife.

Think of fruit growth as a balancing act between ingoing and outgoing fluxes. When the balance is positive, fruits grow. When it is negative, they shrink—or shrivel. The main fluxes in question are carbon and water, which enter the fruit from the xylem and phloem of the plant vascular system. Water is lost mainly to the atmosphere via transpiration (evaporative water lost through stomata and other pores and from the skin surface). Keeping the ledger positive isn’t an easy job for a fruit. Hot, dry, and windy weather encourages transpiration and thereby increases the odds that a fruit will experience water stress. Excessive sunlight may cause sunburn. Fruits also need to avoid attack from pathogens and herbivores before the seeds within mature. A fruit’s skin—its cuticle and epidermis—is its first line of defense against abiotic and biotic threats. Some fruits resort to creative coverings to get the job done.

Here I’ll take a close look at the skin of kiwifruits. Why, exactly, are they so fuzzy?

A heart-shaped green kiwifruit (Actinidia chinensis var. deliciosa), covered in fuzzy trichomes

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Pirates of the Carob Bean

Maybe the name takes you back to gentler days of Moosewood Cookbook and the dusty spicy local co-op. Or maybe you were a kid back then and fell for a chocolate bait-and-switch. Whether you are sweetly nostalgic or wary and resentful, it’s worth giving carob another chance. Katherine argues that it’s time to pull this earthy crunchy 70’s food into the superfood age. She offers foraging tips and recipes to help you get to know carob on its own terms.

From November through January, the carob trees in my neighborhood dangle hard, lumpy, dark brown fruits resembling lacquered cat turds. They are delicious and nutritious and of course I collect them. I am, without apology, a pod plundering, legume looting, pirate of the carob bean. CarobPiratesIf you seek adventure and happen to live in California, Arizona, or on the Mediterranean coast, you can probably pilfer some carob fruits yourself and play with them in your kitchen. If you lack local trees or the pirate spirit, you can order carob powder and even whole carob beans with one simple click.

Although plundering season begins just as the year is ending, I always wait until January to gather carob fruits for two reasons. First, carob functions mainly as a healthful chocolate substitute, and during the holiday season, fake chocolate just seems sad. In January, however, eating locally foraged carob feels virtuous and resourceful. Second, November and December are when my local carobs make the flowers that will produce the next year’s crop, and those flowers smell like a pirate’s nether parts after a shore leave. Or so I imagine, and not without precedent. A man who should have been inured to such salty smells, Pliny the Elder, natural historian and commander in the Roman Imperial Navy, described the flowers as having “a very powerful odor.” It’s not clear why these flowers have a sort of seaman scent, since the main volatiles wafting from the flowers – linalools and farnesene – smell like lilies and gardenias (Custódio et al., 2006). In any case, I keep my distance until the flowers have finished mating season.

Carob trees

Despite their stinky flowers, carobs make great street trees and produce a valuable crop in many Mediterranean-type climates. They are beautiful, tolerant of dry and poor soils, pest resistant, and tidy. Carobs are legumes – like familiar peas and beans – but they belong to a different branch of the legume family (Caesalpinioideae), one that contains mostly trees and woody shrubs with tough inedible fruit (Legume Phylogeny Working Group, 2017). Carob pods look about as edible as Jack Sparrow’s boots, and the species’ scientific name, Ceratonia siliqua, means “horny long pod,” which well captures the intimidating nature of their leathery fruit. But as you will see below, the fruits are easy to harvest and process, and their sweet pulp is worth seeking out. Continue reading

A holiday pineapple for the table

This deep dive into pineapple anatomy is our contribution this year to the very fun Advent Botany essay collection, a celebration of plants that are at least somewhat tangentially connected to the winter holidays. In previous years we’ve contributed essays on figs, peppermint, and sugar.

December is the time to bring out the fancy Christmas china, polish the silver pitchers, and . . . bedeck your best bromeliads. In 2017, as in 1700, no proper hostess can be without a pineapple for her centerpiece. Here we unpack the botany of pineapple, which is as complicated and fabulous as its cultural history. A proper hostess, after all, should also be able to dazzle her guests with tales of tropical fruit morphology. Continue reading

#Celery

It’s hard to get too excited about eating celery, but if you can manage to see a dip-drenched celery stick as a dynamically loaded cantilevered beam, then its stringy bits suddenly start to look like incredible feats of bioengineering. The mildest mannered member of the crudité platter turns out to be a misunderstood superhero.

If you are about to celebrate Thanksgiving, chances are good that you have a lot of celery in your immediate future. It shows up in dressing and cranberry relish and especially in leftovers, like turkey salad sandwiches. When I was growing up, my sister and I were tasked with picking the carcass for turkey hash, which, in our family, was basically turkey soup stretched with lots of celery and potatoes and never enough salt. Although frugal and nutritious, this one-pot crusade against food waste did not inspire a lifelong love of cooked celery. But you don’t have to like celery the food to admire its alter ego, celery the plant.

Leaves, not stems

Celery the food may not excite you, but celery the plant – the bundle of dynamically loaded cantilevered beams – is a biomechanical superhero worth exploring in the kitchen. Celery (Apium graveolens) is one of the clearest examples of how a plant’s life in the wild over tens of millions of years yielded anatomical adaptations that determine how we use it now. Because of its evolutionary responses to biomechanical challenges, it is now perfectly built to hold peanut butter or scoop dip, and when sliced, its crescent moon shapes are pretty in soup and chopped salads. On the other hand, its tough strings catch between teeth and are not easy to digest.

Celery stalks are the petioles (“stalks”) of compound leaves. They are not stems, in spite of widespread misrepresentation in elementary school lesson plans. They may look like stems to some people because they are thick and fleshy and have prominent veins running lengthwise through them. But there are several morphological clues to their leafy identity, including these: Continue reading