Category Archives: Garden

Caterpillars taking their tithe of the carrot tops

Nightly frosts brush the garden, but botanical energy continues to surge. Carrots, lettuces, and chard are all thriving in the cool sunshine. Black swallowtail butterflies have tapped this energy, laying eggs on the carrot leaves. The caterpillars fall into an inert stupor during the cold nights, but turn into animated single-minded leaf-munchers when the sun touches their skin. They are all in their last stage of molt. The next step will be transformation into overwintering pupae.

For reasons unknown to me, Linnaeus named many swallowtails for prominent figures in Homeric/Greek poems. The black swallowtail is named (polyxenes) for Polyxena, the daughter of Priam, King of Troy. She does not appear in the Iliad but other accounts tell that her death marked the end of the Trojan War. The connection between these tales and North American butterflies seems tenuous, at best. But Linnaeus invented the rules of nomenclature, so he could do as he pleased.

Our caterpillars need not fear Achilles and, with luck, the birds will not find them.

Quicksilver

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After heavy rain, water turns mercurial on nasturtium leaves. The water balls into a skittering drop, seeming to float just over the leaf’s surface. I was reminded of chasing liquid metal over chemistry lab benches in the days before kids were protected from such amusements. But similar delights, minus the metabolic cost, await in the garden.

The drops were dancing. Water on the leaves of other plants was sluggish, gathering in flat pools or damp stains. These plants were wet, soggy, but the nasturtium leaves were perfectly dry, even where silvery drops had sat a few seconds before.

A recent paper by James Bird and colleagues in Nature reported that nasturtium leaves are covered with “superhydrophobic ridges” (literally, “super-water-fearing ridges”). These minute structures on the leaf surface exert a strong repulsive force on water. When a water drop hits the surface, the repulsion is so strong that the drop recoils, shatters into minute droplets, and jumps back into the air. The Nature paper does not mention this, but my observations suggest that nasturtium leaves only shed large drops. On dewy mornings, smaller drops manage to cling, although they still sit as silvery globes.

Leaves of almost all land plants have a waxy covering that keeps water away from the core of the leaf and eventually causes water to run off. But on nasturtium leaves, water doesn’t just run, it springs and sprints. Nasturtium beats even the former superchampion of “hydrophobicity,” the water-shedding upper surface of lotus leaves. What function might this serve? We do not know, but shedding water must surely combat fungal infections by depriving spores of damp places in which to germinate.

All this makes for ephemeral beauty in the garden. It may also be of practical importance. Surfaces that vigorously repel water not only stay remarkably dry, but they self-clean and resist icing. Engineers would love to incorporate these features into all kinds of surfaces, especially cloth, windows, painted walls, airplane wings, and the insides of ketchup bottles (the BBC has a nice overview).

I look forward to venturing into the woods clad in a coat of nasturtium, a fig leaf for rainy climes.

Bee comb

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This week I took advantage of what may be the last warm, sunny days of the season to tidy up the bee hives for winter. I removed unneeded boxes of frames from the tops of the hives and shuffled frames within the boxes to keep as much honey in the hive as possible. Thus prepared, winter hives are less likely to blow over in storms and, more important, all the honey is gathered into one place within the hive. In cold winters, bees huddle in a ball around their honey stores, slowly eating the honey as fuel to keep them warm (the center of the hive is as warm as human body temperature). If honey is thinly dispersed, the balmy bee ball cannot form.

I had forgotten just how beautiful the wax combs of honeybees are. The near-perfect six-sided geometry, repeated hundreds of times is a fabulous piece of natural architecture.

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The wax is secreted from chinks in the abdominal exoskeleton of worker bees. The bees then mold the wax into the six-sided pattern using chewed wax particles. This task falls to middle-aged (2-3 week old bees) worker bees. Younger workers look after the brood; older workers leave the hive and forage.

This weekend marks the 153rd anniversary of the publication of On The Origin of Species. It is therefore fitting to include here Mr. Darwin’s thoughts on the wonders of beeswax.

He must be a dull man who can examine the exquisite structure of a comb, so beautifully adapted to its end, without enthusiastic admiration. We hear from mathematicians that bees have practically solved a recondite problem, and have made their cells of the proper shape to hold the greatest possible amount of honey, with the least possible consumption of precious wax in their construction. It has been remarked that a skilful workman, with fitting tools and measures, would find it very difficult to make cells of wax of the true form, though this is perfectly effected by a crowd of bees working in a dark hive. Grant whatever instincts you please, and it seems at first quite inconceivable how they can make all the necessary angles and planes, or even perceive when they are correctly made. But the difficulty is not nearly so great as it at first appears: all this beautiful work can be shown, I think, to follow from a few very simple instincts. (First edition, Chapter VII, page 224).

He elaborated these thoughts with a series of calculations and experiments, summarized in a recent essay at the Darwin Correspondence Project. As you might expect, Darwin concluded that natural mechanisms could explain the structure of bee comb and that sophisticated combs could have evolved from simple beginnings.

This naturalistic view contrasts with the opinions of Darwin’s contemporaries. After reading Darwin’s passage, I pulled down Langstroth’s Hive and the Honey-bee, an important review of bee biology and bee-keeping published in 1859 (the 4th edition, 1878, is the one that I have on hand; post-Darwinian for sure, although Darwin is not mentioned). Langstroth writes of comb:

To an intelligent and candid mind, the smallest piece of honey-comb is a perfect demonstration that there is a “GREAT FIRST CAUSE.”

These enraptured references to the Divine are peppered throughout his work.

Langstroth was a priest, but depression kept him from many of the usual priestly duties. Instead, he studied insects, especially honey bees. Although his theology seems unsophisticated to modern ears, his entomology was not. His careful studies of bee behavior transformed bee-keeping. In particular, these studies led to him a new design of bee hive, a design that is still the preferred hive for most bee-keepers, especially in North America. Unless you’re eating honey from wild nests, you can almost guarantee that the honey in your kitchen came from a Langstroth hive. I use a modified design: Langstroth in the upper portion (from which come the photos in this post) and open in the lower part (no photos — I never open this part, leaving it for the bees to do as they will).

Crab spider

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Just under the petal’s lip sat a small green spider. The fly landed. The petal twitched. The spider’s tidy fangs sank into the fly’s crunchy exoskeleton.

Next day, the spider sat on the same flower, but this time on the upper surface of a petal. The spider held its arms to the sky, keeping utterly still. Even some pokes from a piece of straw did not break its steely immobility. While I watched, no flies came to visit.

Crab spiders add a streak of danger to the cosy relationship between flowers and their pollinators. There are hundreds of species of these spiders (named, of course, for their crabby look while sitting) and in some habitats (e.g., Sewanee’s fall blooming meadows and roadsides) they are quite common. Their sit-and-wait hunting strategy makes them inconspicuous, but close attention (or the movements of unfortunate flies) will reveal their presence.

How many poems feature thorns and roses? Crab spiders seem so much more interesting. Not just the prick of a thorn, but the dying fall of a poisoned bite. And all the fly wanted was to touch its feet to a flower, to sip a drop of nectar. OK, that’s a pretty overworked theme. How about the flower’s perspective? A display of beauty, a straightforward offering of pollen, yet here come the Arachnid riff-raff, ready to knife the honest customers.

Fall garden emerges

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The slideshow shows a few snapshots of the emerging fall garden (and a gratuitous picture of a Seminole squash bloom — one plant has put on about 200 ft of vine and is still producing). It is very good to see lettuce again after a too-hot summer. I feel healthier just seeing the gentle green of lettuce. Eating is almost an afterthought.

The benign and drawn out autumn weather here make fall gardening quite easy. The weeds grow just a little slower than in the summer and the cooler temperatures are kinder on the soil. Lettuce, Asian greens, and carrots all thrive. And, with a little protection, fall-grown veggies will be good to eat all the way until February.

Unfortunately, a lot of local stores pull their seed racks or offer only turnip greens. If you want to put in a fall garden and need seeds in a hurry, Johnny’s is a good place to start, as is Southern Exposure Seed Exchange. For readers in colder climes, check out Eliot Coleman’s books on winter gardening — the man eats home-grown lettuce in mid-winter in Maine. I can only imagine how good that must look and taste.

“There sleeps Titania sometime of the night, / Lull’d in these flowers”

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Now that late summer is upon us, bumblebee nests are full of worker bees. These bumble-workers often stay out in the field at night, sleeping in flowers. I found this bee in a dewy Yellow Cosmos bloom. She was completely still, paralyzed by the cool morning temperatures.

Like mammals and birds, bumblebees are endothermic, meaning that they warm themselves from internal heat sources. Bumblebees do this by shivering their flight muscles as they wake in the morning. Until they reach running temperature, they are sluggish and can barely move a leg, let alone fly.

In the arctic, some bumblebees use their bodies’ heat to incubate eggs and young bees, just like a mother bird. Without a boost of maternal muscle-heat, the bees would not have enough time to complete their life cycle during the short arctic summer. This endothermic physiology explains why bumblebees, especially northern bumblebees, are furry: like birds (feathers) and mammals (hair), they have a layer of insulation to retain hard-won heat.

Our local bees’ nightly cold stupor saves energy. But immobility is is a dangerous habit, especially for footloose bees who like to sleep outside of the nest in exposed flowers. Yesterday, I watched a European hornet patrolling the profuse blossoms on a clematis vine. Every time it came across a bee or fly, the hornet lunged, trying to grab the victim.

Look sharp, little bee. An evil Puck is after your life.

Ringneck snake

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I found this ringneck snake (Diadophis punctatus) under a piece of firewood from the pile in our driveway. The snake either came as a free bonus with the wood or it colonized the new hiding place in the last couple of days. Either way, the wood is stacked, so the snake is roaming the garden. It is probably joining many others of its kind. This species can, in the right conditions, live at very high densities (hundreds per acre).

I held the snake for just a minute or two, and in that time it demonstrated its two favorite methods of defense. First it writhed around, flashing its bright underbelly at me, then it oozed nasty-smelling saliva from its mouth. Despite a thorough scrubbing, my hands still smell musky. If severely provoked, the snake will bite, but I merely handled it for a photo, then released it, stopping well short of this level of torment. The bite is not dangerous to humans.

Ringnecks are mostly active at night when they hunt for small salamanders, insects, slugs, and any other animal that can fit down their gullet. They, in turn, are preyed on by larger snakes, raccoons, and, occasionally, birds. I’d guess, from the smell, that they taste pretty bad. I usually encounter them under rocks and logs. The contrast between their smooth dark backs and bright bellies makes them one of the more visually appealing (I was going to say…striking…but we’ll leave that word for the copperheads) snakes in our area.

Range maps for the species indicate that this is a “northern” ringneck. But the color patterns are ambiguous. The animal has a complete neck ring (a characteristic of the northern subspecies, D. p. edwardsii), but the belly is patterned (a characteristic of the southern subspecies, D. p. punctatus). Some recent molecular work suggests that this “species” — the ringneck snake whose range covers much of North America — may in fact be a complex of multiple undescribed species. In addition, some of these undescribed species seem restricted to particular habitat types, suggesting ecological as well as evolutionary diversity within the group. So taxonomic revision is coming, I suspect.

Carpentry

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I’ve been using some salvaged wood to make repairs to the goat barn. One of the pieces seemed unusually light. I flipped it over and found a perfectly round hole on one side: the entranceway of a female Eastern carpenter bee, Xylocopa virginica.

The bee that left this hole used her mandibles to gnaw into the wood, then she slowly tunneled through the timber. I’ve seen these bees at work on the rafters of several of the small barns that we’ve built for animals and hay. On a quiet day in early summer you can hear the crunching of chitin on wood as the bees make their slow progress. Below the holes, small piles of sawdust accumulate.

I’ve seen many entrance holes, but never had the opportunity to see the extent of the tunnels inside. So I made a series of longitudinal cuts in my wood scrap, a 4×4 dissection of sorts. Inside, I found the tunnels extended about a foot away from the hole. One or two tunnels branched. This is an impressive hidden network, like a subway with just one exit. No wonder the piece of wood was so light.

The bees make these tunnels for their young. The female makes a ball of pollen and nectar, then lays an egg. All this is sealed into the tunnel with a slug of compressed sawdust. Once the passage is sealed, the mother leaves her offspring to their fates. These futures sometimes involve woodpecker beaks. The drilling of these hungry birds will finish what the bees started. The two species, bee and bird, are an anti-carpentry team. But I also think of these animals as supreme carpenters: they’ve been making homes from wood for millions of years and they spend their lives happily sprinkled with the sawdust of their labor. So they are both über- and anti-carpenters.

Away from wood, the bees do good work as pollinators. They are eager visitors to many species of flowering plant. Some farmers even erect pieces of wood to attract them into their orchards. I’m OK with a few at our place, but a year ago we had an invasion of battalions of barn-destroyers. So I relived my glory days of college squash-playing, dispatching them with a killer backhand from a dustpan. I felt bad, but not as bad as I would have had the barn needed rebuilding. These days we just have a few carpenter bees buzzing around and I leave them alone.

One more smutty webpage

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These are healthy corn tassels, ready to shed their pollen:

And these are tassels that have been infected by a fungus, the “corn smut” (Ustilago maydis; formerly U. zeae):

Smut spores overwinter in the soil, then as the weather warms they blow up onto corn plants and infect leaves, tassels, and ears. Like corn itself, smut is native to Mexico and thrives when the weather is hot and dry in early summer. This Mexican weather came to Tennessee in June, so we’ve had a good crop of fungal growth this year.

The fungus causes grotesque swellings on the corn. These pustules eventually burst and disgorge clouds of dark spores. The whole process is interesting to watch: the civilized, elegant growth of a plant hijacked by an ugly, destructive mob. Depending on your mood, this discord is either disturbing (the world’s order is threatened) or profoundly hopeful (the world’s order is indeed threatened).

Fungal infections are usually unmitigated bad news for gardeners, but this one has a surprising silver lining. The fungus causes uncontrolled growth and swelling of cells in the corn plant, cells that then get filled with…mushroom. In Central America and Mexico, smut is considered a delicacy, called “huitlacoche,” and farmers can get a higher price for infected ears. I was unfortunately not aware of the gastronomic possibilities when I culled the smut from our corn patch. Next year, perhaps?

The word “smut” obviously has another meaning. The etymological common origins here are straightforward: lewd smut and fungal smut are both “dirty.” The Online Etymology Dictionary (one of my favorite websites…a celebration of the anastomosing evolutionary trees of language) traces the word to pre-1500s West Germanic, smutt-, “to make dirty,” through the 1400s where smutten meant “to debase or defile,” then to the 1660s when the word meant both “black mark or stain” and “indecent or obscene language.” There is a botanical irony here, of course. The smut fungus is “defiling” one of the more overtly sexual plants under cultivation, one that sheds its pollen to the air and lets both male and female parts hang exposed (at eye-level, no less; I blush to gaze at a field of corn). But only when these parts become darkened with unbidden strands of fungal desire do they count as smut. Order is indeed threatened.

Snake

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While walking down the garden path, I was stopped by the sight of a black rat snake, its body woven loosely through the low weedy plants. The snake was a youngster, too young to have the heft and scratched hide of a mature adult, but too old to be striped and worm-like. It was about two feet long and was basking in the weak heat of an overcast noon. The snake was entirely still, but its whole being said: alive.

Light hit the snake’s scales and melted. Black. Somehow, an earthy deity had lifted its head from the ground and breathed life into graphite. I’ve never been so captivated by a snake’s quiet presence.

In my admiration and greed, I wanted to catch and remember this beauty. So I walked to the house for my camera. Of course, the snake was gone on my return, leaving a wavy line of pressed vegetation as a mark of its passing.

So far this year, I have not seen the big old rat snake that used to patrol our garden. Even the strong snaky smell around the apple trees has dissipated. This newcomer may have wandered into a deceased old-timer’s empty domain. To stay, I hope.