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Spruce tips

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

chopped spruce tips

Most of this blog is dedicated to the biology of domesticated food plants that you typically find in a grocery store instead of in the wild, but we make the occasional exception for our favorite feral edibles. Some of these are commercially viable and end up in the grocery store or restaurants anyway, or they otherwise straddle the line between cultivated and wild. Okay, the list of our posts on food plants that are at least sometimes wild harvested is actually pretty long: coconuts, macacarobwalnuts and pecansbamboo shootselderberry, maple, onion-y ramps, blueberries, cranberries, and lingonberries, rapunzel, mulberries and figs, strawberriesand some greens. Spruce tips are now a popular beer ingredient, so I suppose they fall into this semi-commercial category, too.

Regardless, spruce tips are easy to collect in the spring, and they make for fun edible projects. Also, kids can eat them straight off the tree, so for the 5 minutes it captures their attention, it can be a family endeavor. The kids definitely will eat spruce tip shortbread (recipe below). This is the first year I’m trying spruce tip salt (recipe below), which I’m told is pretty amazing on roast veg. Folks here also like drying the spruce tips for tea, pickling them, or making them into jelly.

A spruce tip is an immature shoot, complete with needles (Owens and Molder 1973). It is an entire compressed branch, analogous to the telescoping shoot of young asparagus or bamboo shoots and structurally similar to cabbage and Brussel’s sprouts. Picking a spruce tip removes all of this year’s growth for that particular small branch and neuters its capacity to grow outward from that particular point. Be mindful, then, about how many tips you take from a particular branch or tree. 

The best time to collect spruce tips is shortly after bud burst, when the needles are still tightly bound together. In this stage the needle tips may still be encased in a papery scale.

young spruce tips, still capped with bud scales

The scale is actually composed of many overlapping individual scales, which are modified leaves that protect the developing bud over the winter (see the microscope image below of the scales covering an overwintering bud). They are similar to the papery modified leaves covering onion and garlic bulbs.

Fig. 3 from Sutinen et al. (2009): “(A) Longitudinal section of a vegetative spruce bud sampled in the field on 17 January 2007. The primordial shoot is about one-third of the total length of the bud. The line on the bud shows the measuring point of the primordial shoot and that of the whole bud. The bud scales (Bs) are compact and glossy at the outer surface, but delicate and white around the primordial shoot. Bar = 1 mm. (B) Upper surface of primordial shoot from A. Primordial needles are tightly pressed against the primordial shoot and their tips are all blunt (C) giving a rounded appearance to the tips when viewed around the naked, star-shaped apex at the top of the bud. Bars in B = 0.5 mm and in C = 0.2 mm.”

The immature stem and needles are soft and pale green. Lignification (growing tough wood fibers of cellulose and lignin) hasn’t yet begun (Polle et al. 1994), nor has the hardening of the cuticle. Both the epidermis and the inner leaves are still quite immature. Cellular expansion won’t be complete for several more weeks. They have a high water content relative to mature stems and needles, and green chlorophyll-filled chloroplasts are still developing (Hatcher 1990). See the microscope cross-sections below of immature and mature spruce needles to see the loose, thin structure of the new shoot and the low concentration of chloroplasts.

Fig. 1 from Moss et al. (1998): “(A–D) Light micrographs of transverse sections of first-year red spruce needles, collected at the mid-elevation site on Mt. Moosilauke, showing normal developmental maturation over the 1988 growing season. E, epidermis; H, hypodermis; RC, resin canal; S, stomate. (A) Collected June 29, 1988. Note immature light staining of epidermal tissue system and numerous discrete chloroplasts in mesophyll. (B) Collected August 2, 1988. Note dark staining, thick-walled epidermal system and still immature mesophyll. (C) Collected August 17, 1988. Note fully developed mesophyll with discrete chloroplasts characterizing a healthy needle. (D) Collected September 20, 1988. Note discrete chloroplasts and fine granular, light staining of cytoplasmic contents.”

Spruce tips are often described as “lemony.” While they are full of terpenes, including citrus-scented limonene (Puchalska et al. 2008), I think most of this “lemoniness” has to do with their sharp tang, which is due in part because of their high content of ascorbic acid (vitamin C) (Polle et al. 1996). Vitamin C is part of a robust antioxidant and protective suite of chemicals that protect the developing leaves before the epidermis takes over that job. I think they have a bit of an astringent flavor, too, which is from their high concentration of phenols (tannins) (Puchalska et al. 2008).


Hemlock conifer (Tsuga) tips are safe

If you don’t have locally available spruce (genus Picea), fear not: newly emerged branches of some fellow conifers (gymnosperm family Pinaceae; see our Food Plant Phylogeny page for a description of what this means) will work just fine, too, including: pines (Pinus), firs (Abies), Douglas fir (Psuedotsuga), and hemlock (Tsuga). Not all conifers are safe to eat, though. Yew (Taxus), for example, is deadly poisonous. I think it’s crazy that it is a common landscaping plant. Note here that the conifer hemlock in the genus Tsuga that I just said is safe to eat is different from the plant called “poison hemlock” (Conium maculatum), which is the herbaceous plant in the family Apiaceae (carrot family) that killed Socrates.

expanding spruce tips (white spruce)

Also, you’ll find you have distinct preferences for the aroma and flavor of different species. White spruce (Picea glauca), for example, is one of the common spruce species around here and is, in my opinion, the least desirable from a culinary perspective. One of the ways to identify it in the field is to crush a needle and see if smells, like, well, cat peeIt’s perfectly safe, and I can’t figure out which of the compounds in its essential oil or hydrosol (Garneau et al. 2012) are responsible for the unfortunate pungency, but you may want to keep your species separate while you figure out which ones you prefer. I actually didn’t have a problem with the white spruce tips until they were a bit older and I used them in spruce tip salt. We’ll see how it turns out, and I’m definitely going to specifically try black spruce or Sitka spruce next year.

Spruce tip shortbread

Full disclosure here about these shortbread cookies: I genuinely think they’re delicious. My kids said they’re good, and they don’t shy away from pointing out culinary failures. Other grown-ups also claimed they liked them. Before he realized the joke, though, my husband bit into one and asked: “What are these made out of? Twigs?” This recipe is adapted from the NY Times basic shortbread recipe. The addition of cardamom and orange zest was the innovation of Rosey at Jerome St. Bakery

1 cup/125 grams oat or wheat flour (you can make this yourself by pulsing rolled oats in a food processor)

1 cup/125 grams blanched almond flour

2/3 cup/150 grams sugar

1 teaspoon salt

2 sticks/1 cup/226 grams cold butter, cut into chunks

handful of spruce tips, coarsely chopped

1 tablespoon orange or lemon zest (optional)

1 teaspoon ground cardamom (optional)

Treat the ingredients like biscuit dough: either incorporating the butter into the rest of the ingredients by hand with a pastry cutter or butter knives or your hands, or by mixing it all in a food processor or stand mixer (with paddle attachment) until it is still a little crumbly, just before it becomes a solid dough ball (although I’ve done this, and it turns out fine). You can pat the dough into a 9-inch baking pan (to 1/4-inch thickness) or hand-roll it into a log and slice it into 1/4-inch cookies before baking in a 325-degree oven for 35-45 minutes (until golden brown). I prefer the latter option. If you do pat it into a baking pan, cut it into bars or wedges while it’s still warm.

Spruce tip salt

Blend an equal volume of salt and spruce tips in a food processor. Spread the mixtures out to dry on a piece of parchment, or let it dehydrate in a dehydrator or warm oven. It will keep best in the freezer after it’s dry.

References (below) Continue reading

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—hairlike projections from the epidermis—on the skin of kiwifruits 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

Continue reading

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

Carrot top pesto through the looking glass

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

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 peaches cooked into jam and spread across rough toast lose their buttery mouthfeel and dripping juice. To compensate for textural changes, processed 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

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

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)

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


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