Category Archives: Vegetables

Botany lab of the month – August edition: Rocky Top Corn Soup

It’s August, and everyone from the American Midwest knows that late summer means fresh sweet corn, and a lot of it. When I was growing up in Indiana, every few days during corn season we would pick up a dozen ears from my family’s favorite roadside stand, just hours after harvest, and cook them right away, before the kernels could start converting their sugar into starch. 

Corn season typically peaked the final week of the Indiana State Fair, which always fell between my sister’s birthday and mine. We felt like the whole world was celebrating with us since the Indiana State Fair really is just a giant party, with rides and games and food and music and anatomically impressive hogs. So every year we went to revel in the indulgent atmosphere of the fair alongside thousands of unbridled Hoosiers from all over the state sweating in tank tops and showing off their best pickles. But I most looked forward to the corn. The fair was littered with vendors serving huge ears of fresh-picked local corn straight from a grate set up over a large open flame. As soon as the charred husks were cool enough to peel back into a handle, we sidled up next to our fellow Hoosiers at a trough (literally a trough) of hot melted butter and plunged the roasted ears into it, right up to the hilt. Then we gave them a generous coating of salt from oversized aluminum shakers, passed from hand to greasy hand around the trough and down the line to us. Best birthdays ever.

For this month’s botany lab, I have created a cold summer soup that is as much a celebration of decadent State Fair food as an homage to the millennia of cultivation and adaptation that makes that food possible. The soup features corn four ways, and its various ingredients are available to us only because people have been growing corn (more accurately, maize) and creating distinct varieties for a very long time over an unusually wide geographical area. Maize as a crop goes back to Mesoamerica about 9 thousand years ago, and it had become a substantial part of people’s diets there by about 4500 years ago (Kennet et al. 2020). The spread of maize throughout much of North America was slow because the right mutations had to arise before Native Americans could select for genotypes that were well suited to the local day length, season length, and altitude (Doebley 1990). In the process, people created the varieties we know now, including those in the soup: sugary sweet corn, eaten while immature; dent corn, with soft starchy kernels good for grinding into fine cornmeal, masa, and grits; and flint, with hard round starchy kernels that can be popped or ground into polenta.

Photo of a bowl of cold corn soup with bourbon-infused grits croutons and popcorn
Cold corn soup with bourbon-infused grits croutons and popcorn

The Indiana State Fair and its unabashed celebration of big agriculture most probably sits atop ancient hand-tended corn fields. It is important to recognize that the Fairgrounds occupy land that was traditionally held by the Miami Tribe of Native Americans and lost through a series of coercive treaties in the 19th century. Many members were forced to relocate, but not all, and the Miami Nation of Indiana maintains a cultural presence in the state. The many indigenous tribes throughout the region have a long tradition of agriculture, and as far back as a thousand years ago people would have made corn (Zea mays) the main staple of their diet (Emerson et al. 2020).

Now that corn is big business in the US, dent corn is the most widely grown type because it is used for animal feed, corn oil, high fructose corn syrup, and the many processed foods that have become modern dietary staples. The luckiest dent corn, however, ends up as mash to be fermented into bourbon, which brings me to the name of the soup.

photo of the horse Rocky Top. Credit Sara Baggett Preston
Good old Rocky Top. Photo: Sara Baggett-Preston

When I was about to turn 13, my mother, who grew up riding, brought a horse into the family. He was a big palomino named Rocky Top, with a mane the color of corn silk and some Tennessee Walker genes that occasionally showed themselves. Naturally, the Osborne Brothers’ song “Rocky Top” was a favorite in our house, especially since my father was, as he described himself, a “tolerable” bluegrass musician who could sometimes be coaxed into singing it.

Corn won’t grow at all on Rocky Top,
Dirt’s too rocky by far.
That’s why all the folks on Rocky Top
Get their corn from a jar

In the song, Rocky Top is an idyl somewhere down in the Tennessee hills. Personally, when I drink corn from a jar, I choose a nice aged bourbon from Kentucky, but that’s beside the point. As long as it’s mostly corn, with just a bit of rye and barley, I’m happy.

This cold late-summer soup features corn four ways, with different flavors and botanical properties that will be obvious as you prepare it. Observation notes are included in the recipe. Like vendors at the Indiana State Fair, this soup plays around in the corners of midwestern and southern food traditions and comes up with something new and delicious. The fresh raw corn base is almost dessert like while croutons of bourbon-soaked grits add intense corn flavor infused with smoke and caramel, and a scattering of buttered popcorn balances the sweet creamy texture of the soup with salty crunch. The soup’s name, of course, honors the inimitable Rocky Top, who was a beloved equine member of our family for over thirty years. The croutons and popcorn might even remind you of rocky outcrops in the Tennessee hills.

Rocky Top soup with corn four ways

Serves 4-6

The preparation is simple, but leave ample time to cook the stock and grits and to chill the ingredients at various stages.

Ingredients

6 large or 8 medium ears of fresh sweet corn in the husk, preferably from a local farm stand or farmers market and as recently picked as possible

1/2 cup of uncooked grits, stone-milled if available, but definitely not “quick”

1/2 cup bourbon (corn in a jar)

1/4 cup unpopped popcorn

Salt (both regular and smoked, if you’ve got it)

Black pepper

White pepper (optional)

1 stick of butter (or olive oil for a vegan version)

Cold soup base

This part of the recipe is quick; my observation notes are long.

1. Before removing the husks, use a large knife to cut the top inch or two from each ear. If insect larvae have gotten into the ears, this is where they will be, and you may prefer not to see them.

2. Remove the husks, which are leaves enclosing the bud of a giant flowering stalk. Notice their shape and the arrangement of their veins, then take a look at the short bit of stem at the base of the ear to see its scattered vascular bundles. Corn (Zea mays) is typical of monocots in having long narrow leaves with parallel veins and vascular bundles scattered throughout its stems (not in a clear ring). Wash and save the tender inner layer of husks for the stock.

Click to enlarge

3. Look closely at the corn silk and notice that the strands seem to originate from between the kernels. That is because each one is (or was) attached to the top side (the side facing the tip end) of a single kernel. Amazingly, a strand of silk is the extremely long stigma and style through which germinated pollen grains traveled to fertilize the cells inside what is now a kernel. Sometimes you can see that the silk strand is rough or slightly hairy on one side, the better to capture pollen with. (For more details, see Jeanne’s terrific essay, Super Styled.)

Corn silk emerges from between kernels
Corn silk emerges from between kernels
Close up of corn silk, showing pollen-catching hairs
Close up of corn silk, showing pollen-catching hairs. Click to enlarge.

4. Rub the ear under water to remove as much silk as possible. Their race is run, and their job is done.

5. Take a moment to appreciate that each kernel of corn on a cob was once a flower, embedded alongside other flowers in a thick flowering axis. The flowers never had functioning sepals or petals or stamens. (Separate stamen-bearing flowers make the pollen and are found in a tassel on top of the plant). Each flower was essentially a single pistil: an ovary with a style and stigma (those silks!) long enough to protrude beyond the husks where it pollen could find it. The mature product of an ovary is a fruit, so it follows that a kernel of corn is a fruit, not a seed. The fruit functions as a seed, however, because it is essentially just a thin wall fused tightly to the single large seed inside. This type of fruit is called a caryopsis (or, simply, a grain). Fresh corn on the cob is immature, and the fruits are soft, but they would become hard if allowed to mature.

The attachment points of the corn silks (super long styles and stigmas!) are clearest where kernels are uncrowded, near unpollinated flowers. Click to enlarge

6. Cut the kernels off the cobs and into a bowl. First, cut the cobs in half, then stand them on their cut ends and run a large knife down the sides to remove the kernels. When all kernels have been removed, pull the knife blade across the cobs over the bowl to pull out any residual “milk” (actually endosperm, described below).

kernels cut from a cob to show embryo
The corn embryo is embedded in sweet soft endosperm. The kernel is surrounded by a fringe of paleas, lemmas, and glumes.

7. Notice the very small opaque flattened round structures that pop out of the cut kernels and milked juice. These are embryos. The milky juice is endosperm, the tissue that would supply the embryo with energy and nutrients during germination. At this stage, most of the endosperm is soft and some is still liquid. The liquid portion contains many nuclei because it has not yet been divided into walled cells. Refrigerate the bowl of kernels until the stock has been made and cooled.

8. Look closely at one of the empty cobs. Notice that the sockets that once held kernels are ringed with short papery ruffles. These structures – paleas, lemmas, and glumes– are evidence that the corn cob is much more complicated than it seems. Those empty sockets held not one but two corn flowers, one of which simply never developed. The flower pairs were borne on a very tiny branch with two short glumes at its base. Each flower, in turn, was enclosed by a pair of thin structures, one palea and one lemma. The raggedy ruffles are glumes and paleas and lemmas and are left behind when you eat corn off the cob or shave off the kernels with a knife.

9. Place the cobs and the reserved tender husks into a saucepan, add water to barely cover them, and simmer for about 30 minutes to make a stock. Remove the cobs and husks and allow the stock to cool to room temperature.

10. Move the kernels and milky endosperm from the bowl into a blender and add about 1/4 cup of the stock. Blend very well until the soup is a fine silky purée. Add small amounts of the stock as needed to ease the blending and achieve the consistency you prefer. Salt very sparingly; you want to retain the grassy sweetness of the raw fresh corn. Chill thoroughly.

This soup should be made no more than a day ahead for peak flavor. It is raw and may start to ferment after several days.

Grits croutons

In a pinch, you can use polenta, but the texture will be less interesting and the cuisine will be less American. 

1. Place the grits and the bourbon in a heavy-bottomed saucepan, and allow the grits to soak for 30 minutes.

2. Notice that grits, especially traditional stone milled grits, vary much more in particle size than polenta does. Could that be why most people treat “grits” as plural and “polenta” as a singular mass noun? It won’t be obvious, but grits are generally made of dent corn and polenta is made of harder flint corn.

4. Add a tablespoon of butter, a teaspoon of salt, and several grinds of white pepper (about 1/4 teaspoon). If you have smoked salt available, use it here.

3. Cook according to the directions for your particular grits. If you have leftover corn cob stock, use it, supplementing with water if needed.

4. Continue to cook and stir the grits until they are thoroughly done and very thick, like mashed potatoes. You may need to cook longer than directed to get the grits thick enough.

5. Spread the grits into a couple of buttered loaf pans or a square cake pan and chill them for at least an hour, until they are well set. The grits should be about half an inch thick in the pan.

6. Use a table knife to cut the chilled grits into one-inch squares and turn them out into a roasting pan. Toss them with soft butter or olive oil and bake them at 350º for 20 minutes or until crispy on the outside. (It is also possible to fry them in a pan, but they tend to fall apart because they are more fragile than polenta squares.)

7. Croutons should be room temperature or warm but not hot when you serve the soup. You want to keep the soup cool. Croutons may be reheated if needed.

Popcorn topping

1. Notice that popcorn is hard because it has been allowed to mature before harvest, and the once liquid endosperm has been divided into separate cells containing the previously free floating nuclei. Popcorn is a variety of flint corn, so it has a round end without the depressed center seen in dent corn. The nutritive endosperm of popping corn is much starchier than sweet corn would ever get. Although popcorn seems very dry, there is some residual water inside. When heated, that water becomes steam and swells the starch until it bursts the kernel open.

2. Pop the popcorn using your favorite method. Admire the fluffy white expanded endosperm.

2. Butter and salt the popcorn generously, using about 4 tablespoons of melted butter.

Assembling the soup

1. Pour the chilled soup into bowls

2. Scatter several grits croutons over the soup. Most will sink

3. Top generously with popcorn and grind some black pepper over the top

4. Serve immediately to maintain the contrasts in temperature and texture

References and resources

My favorite sources of stone-milled grits are Anson Mills and Nora Mills. Anson Mills also sells popcorn and their website has several interesting pages about the history and botany of the foods they mill.

Doebley, J. (1990). Molecular evidence and the evolution of maize. Economic Botany, 44(3), 6-27.

Doebley, J. F., Goodman, O. M., & Stuber, C. W. (1986). Exceptional genetic divergence of northern flint corn. American Journal of Botany, 73(1), 64-69.

Emerson, T. E., Hedman, K. M., Simon, M. L., Fort, M. A., & Witt, K. E. (2020). Isotopic confirmation of the timing and intensity of maize consumption in greater Cahokia. American Antiquity, 85(2), 241-262.

Kennett, D. J., Prufer, K. M., Culleton, B. J., George, R. J., Robinson, M., Trask, W. R., … & Gutierrez, S. M. (2020). Early isotopic evidence for maize as a staple grain in the Americas. Science Advances, 6(23), eaba3245.

Nickerson, N. H. (1954). Morphological analysis of the maize ear. American Journal of Botany, 87-92.

Weatherwax, P. (1916). Morphology of the flowers of Zea mays. Bulletin of the Torrey Botanical Club, 43(3), 127-144.

Mberkery1, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons

The leftovers of 2020

Do you still have a bunch of celery leftover from Thanksgiving in the back of your fridge? With no holiday parties this year, you won’t be able to sneak it onto a holiday crudités platter. You could assemble silly little peanut butter and celery reindeer snacks, but that would just generate messier leftovers. Katherine tells you why you should put it all into a very elegant silky soup for the grownups.

Some of my happiest teaching days begin when I drag a rattling cartload of vegetables and razor blades over the paving stones and across the quad to my classroom. Then, for a couple of hours, edible roots and stems and leaves are handled, poked, hacked at, licked, bitten into, and passed between lab partners. Some of them become projectiles. Most become snacks right there. Potatoes fall into backpacks to be cooked later in the dorm. By the time we clean up, the scant inedible scraps fit into one small bag that I can tip inconspicuously into a campus compost bin.

It’s hard to imagine those days now. Before the pandemic, the only real potential hazards of these labs were food allergies and dissecting tool injuries. While I did provide hand wipes, nobody used them. Now after nine months of pandemic protocols, even just describing the labs triggers aversion.

Trying to teach botany during a pandemic is exactly why I ended up with leftover celery, and much too much of it. The week before Thanksgiving, Jeanne and I taught a virtual botany lab by video conference with some of the volunteers for the Friends of Edgewood Park. We imagined a plant-based Thanksgiving dinner and walked the volunteers through each of the main plant ingredients, while they dissected their own samples at home. The participants were good sports, and it was fun, even if nobody started a Brussels sprouts fight.

Celery (left) and fennel (right)

Celery (left) with close relative fennel (right)

After the event, it was a boon to have the remaining potatoes, sweet potatoes, herbs, leeks, oranges, green beans, and cranberries I had gathered for the demonstration. They were mostly still intact and free from community spittle, and I had plans for each of them. But then there were also those two imposing bundles of celery – stringy, strong tasting, and too long for the fridge. There was nobody I could send them home with. I certainly did not want to eat that much raw celery. Braising it à la Julia Child was no more appealing as I have always hated cooked celery.

Or so I thought. After consulting with Jeanne, a genius with umbel-bearing species, I improvised a basic celery and potato soup and added a little bit of the leftover rosemary. Slow cooking and a whirl in the blender transformed it into something silky and rich and delicious, without any of the strong overcooked green flavor I associate with celery chunks in soup. The recipe is below. But how did this simple treatment completely change the celery flavor?

base of a bunch of celery, showing leaf arrangement

Base of a bunch of celery, trimmed to show leaf arrangement

Fortunately for us all, the amazing Harold McGee has just published an instant classic, Nose Dive: a Field Guide to the World’s Smells. For his book, McGee has compiled table after table of the dominant smells (and their source molecules) for a wide array of vegetables and herbs, including celery. His painstaking work helped me understand why I should stop omitting this complicated species from my mirepoix.

From heavy scented to heaven scented

Raw celery has a fresh green scent to match its crisp texture, but it’s not bland, and it won’t hide behind the rest of the crudités on the platter. Its scientific name is Apium graveolens, and while the genus name has something to do with bees, the species name means “heavy-scented.” Its distinct celery smell comes largely from a volatile molecule called sedanenolide, which is a type of phthalide (McGee 2020). As assertive as it can be, this molecule affects our perception even at concentrations below what we can detect. One study found that a small amount of sedanenolide added to chicken broth raised all eleven measured positive flavor qualities relative to plain broth, as rated by a panel of tasters (Kurobayashi et al. 2008). So in addition to contributing a bit of its own flavor, the sedanenolide in celery boosts our sense that a dish is thick, savory, and complex.

Sedanenolide is not altered chemically by boiling, although it is volatile so some of it probably evaporates when celery is cooked. But cooking celery also transforms some of its chemical components to generate a completely different flavor arising from my new favorite molecule, sotolon.

Sotolon is described as tasting like fenugreek, which may not be helpful information if you have never tasted fenugreek by itself. Fenugreek seeds taste like maple syrup, but with a funky edge that veers into what some authors describe as “curry” at higher concentrations. It reminds me of the faint onion scent that lingers in the wood grain of a well used cutting board.

Fenugreek seeds. Click to enlarge.

Sotolon also contributes warm maple-like flavors to sherry and Madeira wines. I sometimes add it to oatmeal along with cinnamon, cloves, nutmeg, and ginger. You have to be careful with ground fenugreek, though, because the scent remains on your fingers all day, and you don’t want your oatmeal tasting faintly of onions. Reading about sotolon made me crave it, so I spiked some tea with fenugreek, and alongside the maple flavor, I caught occasional hints of celery seed in the steam.

Rosemary

Thanks to McGee’s masterful book, with an incredible index, I learned about some of my soup’s other scents as well. For example, cooked potatoes develop a nutty and earthy flavor because of pyrazines. Of course they also carry some sweetness from the carbohydrates stored in their flesh. Rosemary contains several interesting molecules that give it a resinous camphor scent, but in the soup, the rosemary notes mainly reflected its more woodsy compounds, borneol and peppery rotundone.

Borneol is a monoterpenoid that contributes to the scent of some pines and cypress, as well as ginger and citrus peels (McGee 2020). Rotundone is the sesquiterpenoid molecule that imparts a characteristic black-pepper aroma to Australian shiraz wines, and that’s where it was first discovered in 2008. It has since been identified in (of course) French syrah, some other wine varietals, black pepper, rosemary, basil, and even apple and mango (Geffroy et al. 2020). A substantial proportion of unlucky humans cannot smell rotundone at all. In one panel of French wine professionals and connoisseurs, 31% failed to detect it (Geffroy et al. 2017). Sadly, in COVID times we have all learned the term for this: anosmia.

With all that maple pepper woodsy pine aroma wafting from the bowl, no wonder my simple little three-plant soup turned out to taste like a walk in the woods on a sunny early winter’s day. Not bad for leftovers.

Portion of an advertisement from 1951 for Campbells soup

Portion of a 1952 advertisement from Better Homes and Gardens for Campbells soup. Click to enlarge.

Leftover celery and potato soup

  • Celery stalks (petioles, the part of the leaf below the flat compound blade)
  • Unpeeled chopped potatoes, at twice the volume of the celery. I used several small waxy types and a baking potato because they were left over from the virtual lab demonstration. The type may not matter that much
  • Several tablespoons of butter (1-2 tablespoons per bunch of celery)
  • Olive oil
  • Fresh sprig of rosemary, 2-3 inches long
  • Salt and pepper to taste

Chop celery petioles (“stalks”) and take note of their raw volume. Put the celery and the sprig of rosemary into a large stock pot and cook them slowly and gently in a generous dollop of butter, about one mounded tablespoon for each bunch of celery.

When the celery is very soft and translucent, but not brown, add chopped potatoes. The volume of potato  should be about twice that of the raw celery. Add a dash of olive oil and stir for a few minutes but do not brown the vegetables.

Add water to twice the depth of the vegetables and simmer until the potatoes are completely soft. Add salt and pepper.

Remove the rosemary sprig, but leave any leaves that have fallen off of the stem. Let the soup cool and purée it. Reheat to serve and add water to thin if necessary.

I was lucky enough to have some fresh goat cheese flavored with fennel pollen and black pepper from Pennyroyal Farm. I put a quenelle rustique (a plop) of cheese in the bottom of each bowl and poured the soup around it. Fennel is in the same family as celery, but its florets and pollen produce their own lovely set of volatile scents (Ferioli et al. 2017) that complement the celery without replicating it.

References

Ferioli, F., Giambanelli, E., & D’Antuono, L. F. (2017). Fennel (Foeniculum vulgare Mill. subsp. piperitum) florets, a traditional culinary spice in Italy: evaluation of phenolics and volatiles in local populations, and comparison with the composition of other plant parts. Journal of the Science of Food and Agriculture, 97(15), 5369-5380.

Geffroy, O, Descôtes, J., Serrano, E., Calzi, M.L., Dagan, L., & Schneider, R. (2018). Can a certain concentration of rotundone be undesirable in Duras red wine? A study to estimate a consumer rejection threshold for the pepper aroma compound. Australian Journal of Grape and Wine Research 24: 88-95.

Geffroy, O., Kleiber, D., & Jacques, A. (2020). May peppery wines be the spice of life? A review of research on the ‘pepper’aroma and the sesquiterpenoid rotundone. OENO One, 54(2), 245-262.

Kurobayashi, Y., Katsumi, Y., Fujita, A., Morimitsu, Y., & Kubota, K. (2008). Flavor enhancement of chicken broth from boiled celery constituents. Journal of Agricultural and Food Chemistry, 56(2), 512-516.

McGee, H. (2020). Nose dive: A field guide to the world’s smells. New York, NY: Penguin Press.

The Botanist Stuck in the Kitchen, rummaging for beets

Over these many weeks, humans have been forced into an uncomfortably close study of our own species’ behavior. Observations haltingly stream in through the internet and the TV, through hurried forays into the sparse public square, and through sometimes painful introspection. We are finding what we’ve always known, that humans are petty and petulant, compulsively social, and surprisingly sublime.

Meanwhile, without our clueless interference, non-human animals have gone about their business as normal. The male bi-colored redwing blackbirds where I live are putting on the biggest and flashiest red patches I’ve seen in years. Good luck, guys!

And the Canada geese, which normally annoy me with their poop and their nasty moods have become adorable as they sashay in pairs down the road towards their new nests on the empty golf course. In a few weeks they will be justifiably nasty again, hissing as they protect their babies from me, a silly runner, just trying to shed my own cranky mood into their territory.

Recently, after a run through a muddy patch of the trail stamped with goose footprints and lined with wild sea beets, I remembered that I had some old beets in the refrigerator. Time to do some botany!

For much more information about beets and their relatives, see our longer posts.

Botanizing in the kitchen with kale

The farmer’s market this weekend in late March of 2020 was disorienting, and not only because I was wearing a mask and gloves. It was hard to see which line of widely spaced people was snaking into which farmer’s stand, and many vendors had hung tarps and were helping customers through windows. But everyone was as community-spirited as usual, and many of us were uncharacteristically patient.

Yet again, I was beyond grateful for both the opportunity and the means to fill my fridge with fresh green vegetables, including kale. And I was way more excited than usual to find a bunch of kale that had started to elongate its stem and flower because I knew I could use it in another video in our special COVID-19 series of dispatches from our kitchens.

Here’s hoping you stay in good health and good spirits.

 

For many more details about Brassica oleracea see Jeanne’s many terrific posts from the past that cover B. oleracea diversity, chemistry, and comparative morphology.

The Botanist Stuck in the Kitchen, Saturday night artichoke edition

Welcome to another installment of our new special feature: a series of videos and posts that bring you into our kitchens as we join millions of people sheltering in place. So far, my local farmers market is open for business and local farmers are continuing to bring fresh food to our community, at some real risk to themselves. So so many of us are grateful.

I was lucky enough last week to pick up some gorgeous giant artichokes to prepare for Saturday night, which presented the opportunity for a virtual botany lab. Wherever you are sheltering, I hope that you are able to find some for yourself. Artichokes are full of antioxidants, specifically polyphenols, that have generally health-promoting effects. They are also rich in dietary fiber, which is a good thing if you have spent too much time on the sofa lately. And if you eat them with melted butter or olive oil, well, that can’t hurt your mood, now can it?

This video was only lightly edited and entirely unscripted, so please be patient with the pace and the occasional interruption by Caltrain.

For more details about artichokes, see my written explanation in an earlier post: How to make an artichoke: the facts about bracts, part 1

 

 

The Botanist Stuck in the Kitchen

It’s the spring of 2020, and like millions of others, we Botanists in the Kitchen are sheltering at home, trying to help flatten the curve. In other words, we are stuck in the kitchen. However, neither of us is complaining right now. Personally, I (Katherine) feel secure in my home, and I am (for now) healthy. I have access to fresh and nutritious food (thank you small-holder farmers), and at the end of the day I can go for a long run along a lovely creek lined with trees and birds. Both are opportunities to connect with plants, and this blog has always been about helping people connect to plants that might just be sitting in their refrigerators.

Like many other educators, I have also been preparing to teach a spring quarter botany course, from my sofa, through a laptop. In rethinking what is essential to the class and what might be necessary for my students in this moment, I decided to assign a new reading. It’s a 2015 study by some Stanford colleagues who found, basically, that a walk through a natural green space reduced anxiety compared to a similar walk through an urban area. Maybe that’s not surprising, but they also investigated potential mechanisms by measuring the way people’s brain activity differed in the two situations. Their data suggest that an immersive experience in “nature” (with plants) reduces the kind of unproductive rumination that feeds anxiety. Nobody has done the same experiment comparing our anxiety levels after scrolling through social media or after carefully preparing broccoli and marveling at the fractal arrangement of its unopened flower buds. I do have a prediction, though. Under the current conditions, maybe it’s time to move into the kitchen and see what’s in the fridge.

 

P.S. If you are food-secure and financially able at this time, please consider giving to your local food bank. Everyone should have nutritious fresh food for body and mind.

Reference

Bratman, G. N., Hamilton, J. P., Hahn, K. S., Daily, G. C., & Gross, J. J. (2015). Nature experience reduces rumination and subgenual prefrontal cortex activation. Proceedings of the national academy of sciences, 112(28), 8567-8572.

Botany lab of the month: Contrasting brassica plants in the garden

This is just a quick post about some instructive cruciferous vegetable (family Brassicaceae) anatomy and within-species diversity apparent in my garden at the moment.

Red Russian kale, rutabagas, and canola oil are all different varieties of Brassica napus. Red Russian kale and rutabagas are in my garden now, and the amplification of leaves and roots, respectively, through domestication is evident.

Red Russian kale (Brassica napus)

The rutabaga leaves are large, lobed, and somewhat grayish, like the Russian kale, but they are tougher and not as numerous as on the kale.

rutabaga plant (Brassica napus; Brassicaceae)

You’ll just have to take my word for it that there is no giant rutabaga-like root (technically a swollen hypocotyl, the fused lower stem and taproot, like a turnip, radish, or maca) straining the soil surface on the kale plant.

rutabaga

Anatomical differences amplified through domestication on otherwise vaguely similar-looking cruciferous vegetable plants is also visible on Brussels sprouts and collard greens, two different varieties of Brassica oleracea. A farmer or gardener familiar with the gestalt of the plants will easily identify a Brussels sprouts plant from afar as distinct from a collard greens plant, although the large plant and leaf size are similar.

Brussels sprouts plant (Brassica oleracea)

collard greens plant (Brassica oleracea)

Up close, though, you’ll see that the larger, more tender collard greens leaves have only a very tiny bud in their leaf axils (where the leaf joins with the stem).

Giant collard green leaves subtend very tiny axillary buds.

The developing Brussels sprouts, though, are not nearly done growing and are already much larger than the axillary buds  in any other variety of B. oleracea.

Young Brussels sprouts are really just giant axillary buds developing on the stalk.

While red Russian kale is Brassica napus, most of all the other kales are leafy varieties of Brassica oleracea, along with collard greens, Brussels sprouts, cabbage (which is the enlarged terminal bud, similar to the axillary bud), kohlrabi, broccoli, and cauliflower (read about this diversity and more about the anatomy involved in our essay The extraordinary diversity of Brassica oleracea). Last year we let one of the B. oleracea kales, a curly green winterbor variety, overwinter. Many of these brassicas retain the biennial life cylce of their weedy Mediterranean ancestor (read about it in our essay Caterpillars on my crucifers: friends or foes?), so overwintering is something for which a kale plant can prepare itself. The term biennial means that the plant’s life cycle requires two years to complete. In the first year the plant produces a profusion of leaves (the “rosette”). In the second year the plant flowers, sets seed, and dies. The leaves from the first year die over the winter. It is the job of those axillary buds to survive the winter as tightly wrapped bundles of overlapping leaves that will be familiar to Brussels sprouts fans. In the spring those leaves in the axillary buds unfurl and grow as the tiny stem that supports them elongates. This unfurling of leaves from otherwise small axillary buds was apparent this spring in our overwintering kale.

This winterbor kale stem overwintered. Above each leaf scar (from last year) new leaves are expanding on a new lateral stem from the axillary buds.

If you’d like to read even more about cruciferous vegetables in the mustard family (Brassicaceae), we have a few other longer essays that fill in some of this back story:

Thanksgiving turnips and the diversity of the genus Brassica

The most political vegetables: a whirlwind tour of the edible crucifersGreens: why we eat the leaves we do

Maca: A Valentine’s Day call for comparative biology

The Beet Goes On

In this Valentine’s Day edition, Katherine brings you a love song with a beet. Sweet and red, sort of heart-shaped, bearing rings, and definitely divisive – beets should be the unofficial vegetable of the holiday. And if you don’t feel like celebrating, then you can just sit alone and eat dirt.

Throughout two years of dating and our first six months of marriage, my husband and I had never discussed our feelings about beets. Then again, I had never made beets for him before. When I did, they were a cheap but healthy way to bulk up a vat of stew that would feed us every night for a week. In my husband’s version of the story, it lasted for three weeks. “I hope you like beets,” I announced that evening. “I may have added too many.”

Whether you love or hate beets, it is probably because they taste like dirt. Some people (my husband) can’t get over the flavor, and others can’t get enough of it. Some people experience beeturia, the appearance of bright red or hot pink urine after they eat red beets. Maybe this sight unsettles you. Or maybe you embrace the opportunity to track the transit of beet pigments through your body. You may admire their lovely rings and be inspired by the rich and brilliant colors that beets bring to salads. Or you might have picked up a lifelong aversion after too many canned pickled beets on a school lunch tray. Beets are a pretty polarizing vegetable. If you are among the haters, I’m going to do my best to turn the beet around for you.

Red and white beets

Why beets taste like dirt

Beets taste like dirt because they contain a compound called geosmin (meaning “dirt smell”). Geosmin is produced in abundance by several organisms that live in the soil, including fungi and some bacterial species in the genus Streptomyces. Humans are extremely sensitive to low concentrations of geosmin – so much so that we can smell it floating in the air after rain has stirred it up from the soil (Maher & Goldman, 2017). While people generally like that rain-fresh scent in the air, it’s less welcome elsewhere. For example, we perceive it as an off taste in water drawn from reservoirs with a lot of geosmin-producing cyanobacteria. In wines, geosmin contributes to cork taint. 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

Botany Lab of the Month: Jack-O-Lantern

Happy National Pumpkin Day! Turn carving your Halloween Jack-O-Lantern into a plant dissection exercise.

IMG_7963

The first Jack-O-Lanterns were carved out of turnips in 17th-century Ireland. While the large, starchy hypocotyls (fused stem and taproot) of cruciferous vegetables are anatomically fascinating, this post will be about the stuff you are more likely cutting through to make a modern Jack-O-Lantern out of squash. Continue reading