Author Archives: Jeanne L. D. Osnas

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

Botany Lab of the Month: Jack-O-Lantern

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


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

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

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

Botany Lab of the Month, Presidential Inauguration Edition: Saffron

If you like your spices gold-colored and expensive, find some fresh Crocus sativus flowers and grab ‘em by the…disproportionately large female reproductive organ. Small hands might work best, though it might turn your skin orange. Saffron is probably from the Middle East. If that bothers you, you may want to ban it from your spice shelves, however ill that bodes for the quality of your cabinet. After all, there is a stigma against that sort of thing.

The most expensive oversized reproductive organ in the world


A pile of dried saffron stigmas (“threads”). Photo from Wikipedia

You may know that saffron is the most expensive spice in the world. A Spanish farmer sold his crop of high quality saffron this year for four euros per gram, which is a ninth of today’s price of gold (36 euros per gram). Saffron is expensive because its production requires a huge amount of labor and land. Saffron production is labor- and land-intensive because saffron is a botanically unique food item that defies mechanical harvest and accounts for a miniscule proportion of the plant that bears it. The saffron threads sold as spice are the dried stigmas of the flowers of the saffron crocus (Crocus sativus, family Iridaceae). Recall that the stigma is the part of the flower’s female reproductive organs that catches pollen. Pollen travels from the stigma through the style into the flower’s ovary (collectively, the stigma, style, and ovary comprise the pistil). 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

Botany Lab of the Month, Easter edition

Dying Easter eggs with homemade vegetable dyes today made for some superb kitchen botany. Making the dyes is easy, fun, and offers insight into the fascinating evolution of plant pigments.

2016-03-26 11.58.08

Pigments serve a variety of roles in plants. Many pigments protect plant tissues from sunburn and pathogens and herbivores or perform other physiological functions (see review by Koes et al. 2005). Most noticeably, however, their brilliant colors attract animal pollinators to flowers and seed dispersers to fruit. Humans are also interested in plant pigments, which color and sometimes flavor our food, are potentially medicinally active, and have been used as natural dyes and paints for millennia. Continue reading

Winter mint

This is our second of our two contributions to Advent Botany 2015. All the essays are great!

An early image of candy canes. From Wikipedia

An early image of candy canes. From Wikipedia

The candy cane, that red- and white-striped hard candy imbued with peppermint oil, is a signature confection of the winter holidays. Peppermint has a long history of cultivation and both medicinal and culinary use. Infusions of the plant or its extract have been used for so many hundreds of years throughout Europe, North Africa and Western Asia that the early history of peppermint candies, including cane-shaped ones, is murky. Fortunately, the biology behind peppermint’s famous aroma is better known than the story of how it came to be a Christmas staple. Continue reading