Category Archives: Uncategorized

Kiwifruit 1: Why are they so fuzzy?

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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

Continue reading →

Pirates of the Carob Bean

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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

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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 →

Carrot top pesto through the looking glass

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Isomers are molecules that have the same chemical constituents in different physical arrangements. Some terpenoid isomers have very different aromas and are important food seasonings. A batch of carrot top pesto led to an exploration of intriguing terpenoid isomers in the mint, carrot, and lemon families.

“Oh, c’mon. Try it,” my husband admonished me with a smile. “If anyone would be excited about doing something with them, I should think it would be you.”

The “them” in question were carrot tops, the prolific pile of lacy greens still attached to the carrots we bought at the farmer’s market. I have known for years that carrot tops are edible and have occasionally investigated recipes for them, but that was the extent of my efforts to turn them into food. My excuse is that I harbored niggling doubts that carrot tops would taste good. Edible does not, after all, imply delicious. My husband had thrown down the gauntlet, though, by challenging my integrity as a vegetable enthusiast. I took a long look at the beautiful foliage on the counter.

“Fine,” I responded, sounding, I am sure, resigned. “I’ll make a pesto with them.”

Carrot tops, it turns out, make a superb pesto. I have the passion of a convert about it, and not just because my carrot tops will forevermore meet a fate suitable to their bountiful vitality. The pesto I made combined botanical ingredients from two plant families whose flavors highlight the fascinating chemistry of structural and stereo isomers. Continue reading →

Preserving diversity with some peach-mint jam

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We are knee deep in peach season, and now is the time to gather the most diverse array of peaches you can find and unite them in jam. Katherine reports on some new discoveries about the genetics behind peach diversity and argues for minting up your peach jam.

Jam inspiration

Fresh peaches at their peak are fuzzy little miracles, glorious just as they are. But their buttery mouthfeel and dripping juice are lost when peaches are processed into jam and spread across rough toast. To compensate for textural changes, cooked peaches need a bit more adornment to heighten their flavor, even if it’s only a sprinkling of sugar. Normally I am not tempted to meddle with perfection by adding ginger or lavender or other flavors to peach jam. This year, however, as I plotted my jam strategy, the unusual juxtaposition of peach and mint found its way into my imagination over and over again, like the insistent echo of radio news playing in the background. Peach and mint, peach and mint, peach and mint – almost becoming a single word. To quiet the voice in my head I had to make some peach-mint jam. The odd combination turned out to be wonderful, and I’m now ready to submit the recipe to a candid world. As we will see below, it’s not without precedent. Mmmmmmpeachmint jam. Continue reading →

Maca: A Valentine’s Day Call for Comparative Biology

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Sometimes food is medicine, and sometimes that medicine is an aphrodisiac. Such is the case with Andean staple maca. What elevates this high-altitude root vegetable above its cruciferous brethren?

The ancient Greek Hippocrates, the father of modern medicine, famously said: “Let food be your medicine.” For most of human history, categorizing an edible item as either food or medicine could prove difficult or impossible (Totelin 2015). Even in the current era of modern pharmaceuticals, food and medicine exist along a continuum (Johns 1996; Etkin 2006; Valussi & Scirè 2012; Leonti 2012; Totelin 2015). The traditional Andean food Maca (Lepidium meyenii; family Brassicaceae) can be placed squarely in the middle of that continuum. Herbal medicine markets outside of its native Peru have recently discovered maca and loudly and lucratively promote an aspect of maca’s medicinal reputation that has particular relevance on Valentine’s Day: an aphrodisiac that increases stamina and fertility (Balick & Lee 2002; Wang et al. 2007). Continue reading →

Buddha’s hand citrons and a wish for peace on earth in 2017

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Winter is the season for citrus fruit, and January is the month for breaking out of old routines, so stop staring at your navel and learn about one of the weirder citrus varieties.

I’ll never forget the day one of my general botany students brought to class a Buddha’s hand citron, pulled from a tree right outside our classroom. I had only recently moved to northern California from Indiana, and I’d never seen anything like it: it was a monstrous mass of a dozen pointed twisted fingers splayed irregularly from a stout base. It had the firm heft and girth of a grapefruit and the unmistakable pebbled skin of a citrus fruit, so I wondered whether my student had found a grossly deformed grapefruit; but the oil in the peel smelled heavenly and not at all like a grapefruit. In class we cut through a big finger and found no juicy segments, just white citrus pith all the way through.

Immature Buddha's hand on the tree

Immature Buddha’s hand on the tree

We eventually discovered that this fascinating fruit was a Buddha’s hand citron, Citrus medica variety sarcodactylis, meaning fleshy (sarco-) fingered (-dactyl) citron. Since that day many years ago I’ve become an unapologetic (if surreptitious) collector of the fruits from that same campus tree. The citrons do not drop from the tree on their own, yet I often find one or two lying nearby, probably torn off by a curious tourist or student and then abandoned. Obviously these fruits need a good home, and where better than the window sill in my office?

The first time I left one closed up in my office over a weekend, I opened the door on Monday morning to a waft of fruity floral aroma. It turns out that many people in China and India use the fruit to scent the air, although in west Asia and Europe the fleshy fingers are more often candied or used to flavor alcohol. I do both: the fruits make my office smell nice until they are fully yellow, and then I cook them.

It can be difficult or expensive to get your own hands on a fingered citron, but it’s easy to find a navel orange almost any time of the year. Fortunately, the patterns underlying the morphology of the fingered fruit can also be seen in an everyday navel orange. Between our photos of Buddha’s hands and your own navel orange, you should be able to follow along at home. Continue reading →

Closing out the International Year of Pulses with Wishes for Whirled Peas (and a tour of edible legume diversity)

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The United Nations declared 2016 the International Year of Pulses. What’s a pulse? It’s the dry mature seed of a large number of species in the legume family (Fabaceae): various beans, peas, soybean, chickpeas, lentils, peanuts and other groundnuts. 2016 is days from ending, so it’s high time I get up the Fabaceae diversity post I’ve been meaning to write all year long. This rounds out our year of legume coverage, which included Katherine’s posts on bean anatomy, peanuts, and green beans. 

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Christmas Lima beans (Phaseolus lunatus), soaking before cooking

One out of every 15 flowering plant (angiosperm) species is a legume, a member of the large plant family Fabaceae (Christenhusz and Byng 2016, LPWG 2013). Boasting around 19,500 species in 750-ish genera (LPWG 2013), the Fabaceae is the third-largest plant family in the world, trailing behind only the orchid (Orchidaceae: 27,800 species) and aster (Asteraceae: 25,040 species) families (Stevens 2016). By my count, people only use about 1% of legume species for food (my list of edible legume species is found here), but that small fraction of species is mighty. People eat and grow legumes because they are nutritional superstars, can be found in almost all terrestrial ecosystems around the world, and uniquely contribute to soil fertility in both wild and agricultural ecosystems. Continue reading →

Virgin birth and hidden treasures: unwrapping some Christmas figs

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Enjoy Jeanne and Katherine’s holiday take on figs and figgy pudding which will appear on December 19th in Advent Botany 2016. For a longer read, check out our original 2013 version.

Figs reach their peak in summertime, growing fat enough to split their skins under the hot sun. It’s nearly impossible to keep up with a bountiful tree, and many a neglected fig is extravagantly abandoned to the beetles.  

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Beetles gorge on a fig. Click to enlarge

But here we are, halfway around the calendar in dark and cold December, and we feel grateful for the figs we managed to set aside to dry. Their concentrated sweetness is balanced by a complex spicy flavor that makes dried figs exactly the right ingredient for dark and dense holiday desserts. As we mark another turn of the annual cycle from profligate to provident, what better way to celebrate than with a flaming mound of figgy pudding?

Well, except that the traditional holiday pudding contains no figs. More on that later, along with some old recipes. First, we’ll unwrap the fig itself to find out what’s inside. Continue reading →

Who wants some green bean casserole?

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Is there anything good about green bean casserole? Not much beyond its association with Thanksgiving, so Katherine will be brief and just keep you company in the kitchen in case you are stuck assembling said casserole.

Since this year is the International Year of Pulses, we have been focusing on legumes, whether they count as pulses or not. Green beans do not count as pulses, but only because they are eaten as tender and fresh immature whole fruits. The very same species (Phaseolus vulgaris), when allowed to mature, could yield black beans, white beans, kidney beans, or pinto beans depending on their variety – dry seeds that are perfectly good examples of pulses.

This Thanksgiving week we are going to welcome green beans into the fold and give them a special place. It’s too bad that Thanksgiving so often presents them out of the can, overcooked, with funky flavors, and buried in a casserole. Even Wikipedia promotes this peculiar tradition : “A dish with green beans popular throughout the United States, particularly at Thanksgiving, is green bean casserole, which consists of green beans, cream of mushroom soup, and French fried onions.”

And once again, international observers ask themselves what on earth are Americans thinking? That cannot be good for them. But in the American spirit of inclusivity we invite green beans of all sorts to our tables and try to learn something from them. So if you are preparing green beans this week, take heart, take up your knives, and take a closer look.

The outside of the bean Continue reading →