Tag Archives: farm

Physics on the Farm: Brassica in a Whole New Light

At the farm, we gently wash the vegetables in preparation for the distribution. It’s a meditative process: gently we lay the earth bedecked root crops in the first tub of water. Swish, swish! Swish, swish! One can imagine radish tops as the tail of some exotic koi. One by one, each vegetable in turn, passes through a couple of changes of cool water, so that they’re free of clods and are radiant when you pick them up.


One afternoon, while washing the collard greens, John noticed that the leaves took on a silvery sheen when submerged. Green above water, silver below. What was going on? The answer is a combination of botany and physics.

Collard Green leaves (as well as the leaves of other Brassica) are covered with a waxy cuticle, a waxy layer that the plant secretes to deter pests from munching its leaves. The waxy cuticle makes the leaf slightly waterproof and that means air bubbles adhere to the surface when the leaf is plunged under water. (Fire ants take advantage of a similar development in their exoskeletons when they make waterproof rafts of themselves to cross rivers or survive floods … but that’s another story!)

But why would a miniscule layer of air look all silvery? This is where the physics comes in.
Light bends when it travels from one medium to another medium of a different density. In the case of our submerged collard green, from the water into the air bubble on the leaf’s surface. When passing from a more dense (water) to a less dense (air) medium, it is possible for the light to get “trapped” in the bubble and not be refracted back out again. This happens if the angle at which the light enters the less dense medium is greater than 48.6 degrees. At that angle, the light entering the air bubble is reflected off the boundary between the air and the water and does not refract – bend or have it’s speed changed enough to pass back through the boundary. This results in what is called ‘total internal reflection’, and we see a silvery surface. Neat, huh?


For a more detailed explanation of the physics involved see: http://www.physicsclassroom.com/class/refrn/u14l3b.cfm

For more on the fascinating fire ant rafts see: http://www.uvm.edu/~cmplxsys/newsevents/pdfs/2011/ant.pdf


The Farm Festival Haedalia ~ Hooray! A Success!

What a wonderful day! The weather was pleasantly cool, a true fall day, the farm was resplendent, and the festival was a success!

Blazing yellow chrysanthemums graced the barn entrance where people were greeted by our cheerful crew and had a chance to take a chance on the exotic, elegant, beautiful, tasty, and homey goods being offered in our silent auction and raffle.

Before our very eyes, with paint and brush, Kristina captured the essence of the pasture in her plein air painting demonstration while Molly spun skeins of wool into soft warm woolen thread and Tyler tatted a delicate lace.

The Hetherstons fascinated everyone with their demonstration beehive and vast knowledge of all things apiary.   And the honey they sold from their own bees – how delectable!

Mike with his bike powered wood lathe and metals forge was a wonder to behold.

At the face painting table the children became pirates and princesses and walking works of art.

They grew quiet, mesmerized by the round and round of the potter’s wheel as Sam took a simple lump of clay and, in an instant, drew it up and out into an elegant bowl or vase.  And who could have imagined that a few longish sticks and a hoop or two could provide such hilarity at the children’s game area.

Trip, trip, trip, trot, trot, trot, clomp, clomp, clomp went the three billy goats gruff across the bridge while, “Who’s that tripping, trotting, clomping across my bridge?!” exclaimed the troll. The children gasped as he raised his horn bedecked head and woolly    shoulders up from beneath the bridge. The playlet thrilled and amused everyone, no matter their age.

There were delicious treats to eat, charming shopping bags with the farm’s logo for sale,

and all kinds of information posted everywhere: all about the chickens and what goats eat, the new fruit trees, the tools of our trade, and our many future projects.

Best of all, people stayed to chat, tell stories of their childhoods, breath the fresh air. Parents let their children wander about the meadow and traipse down the secret path.

Young people read books by the paddock, or lay lounging in the grass, or gazed across the peaceful fields, completely at ease in such a welcoming place. Just as it should be, just as we had hoped.

As one little 9 year old observed with a sigh,  “This is the best festival I’ve ever been to.”

You’re welcome, and thank you.

The Mystery of the Missing Kernel

Ever rip open an ear of corn and find gaps where plump kernels should be? Sometimes a whole row will be missing, sometimes a kernel here or there.  Have you ever wondered why that happens?  What makes one kernel develop and another not?  It’s really quite remarkable.  To understand what’s happening, we first have to realize that corn (Zea Mays) is a flowering plant.  By flowering plant we don’t necessarily mean a plant with large showy blossoms or one that richly perfumes the air.  Flowering plants are plants which produce a seed that is protected by a fruit. In the corn plant each corn kernel develops from the female part or ovule of the plant; each kernel is actually an individual fruit with a seed inside.  If the ovule isn’t fertilized by pollen, the fruit won’t develop and voila, gaps amongst the rows of kernels in an ear of corn.

But, as you will have observed, a corn plant doesn’t seem to make it easy for the pollen to reach the ovule given that the male and female parts of the plant are in separate flowers, the tassel (male) and the ear (female), and the cob is so tightly wrapped by leaves.  So how can the pollen get to the kernels?   This is where corn silk comes into play.

Reproductive parts of a corn plant

The tassel on a corn plant is the stamen which contains the anthers, the part of a flowering plant that produces pollen, the male component of reproduction in plants. The silk on an ear of corn is the stigma and style, the means of collecting pollen and providing a pathway to the ovule, the female component of the plant.  Pollen shaken from the tassel by the wind falls on the silk.  It is at this point that the mystery deepens.  In order to form a kernel, how does the pollen get down the silk, under the leaves, and through the ovule wall?  It burrows. Or more precisely, the gamete burrows.  Within a grain of pollen are three nuclei: one whose job is to fertilize the ovum, one whose job is to help produce the endosperm (the kernel, the starchy food for the seed) and a third, whose sole job is to create a tube for the other two to travel down the interior of the silk into the ovule.

A pollen grain forges a path.

Modified from: http://www.agry.purdue.edu/ext/corn/news/timeless/silks.html

Timing is essential for a full ear of corn to occur. Pollen can be released only after the tassel is dry enough, normally mid-morning after the morning dew has been burned off. If the weather is too wet or too dry, the anthers will not open to release the pollen.  Pollen is very light and distributed easily by the wind, which is why it is important to plant corn in a block of rows rather than a single row to increase the likelihood of pollination.  Fortunately pollen doesn’t travel far (from 20 to 50 feet from the parent plant) and silks are covered with fine, sticky hairs that trap the pollen grains.  A pollen grain, once released, can only successfully fertilize an ovule for between 18 and 24 hours.  Fortunately, a single tassel can produce up to 25 million pollen grains and more than one grain of pollen will fall on any given silk. Plus, pollen gametes are speedy!  Pollen tube growth begins within minutes of the pollen grain’s contact with the silk.  A pollen tube can grow the length of a silk (up to 12 inches!) and fertilize the ovule in 12 to 24 hours.

So quite a few things have to go right to grow a single kernel of corn: temperature and moisture levels, silk development timed with pollen release, and pollen viability. And then, of course, there are corn borers and smut to control.  Getting an ear of corn is a bit more complex than one might have supposed!

For more fascinating information about silk growth and the timing of pollination, read: http://www.agry.purdue.edu/ext/corn/news/timeless/silks.html

And for an overview of pollination: http://ohioline.osu.edu/agf-fact/0128.html



  Skunks are adorable with their thick, glossy coats, dainty hands, liquid black eyes, and inquisitive noses.  How do we know?  We accidentally caught one!

One of our farm managers, John Detwiler, noticed that groundhogs would often make their way along the chicken run’s fence line near the old rowboat that is overturned on the rocks between the concrete wall and the fence.  We’ve been having good luck with catching the groundhogs by placing traps at the mouths of their dens or on the paths they habitually travel, so he thought to put one of the Have a Heart traps there.  One morning, on our way out to the fields, John noticed something in the trap and went to investigate.  His “We caught a skunk!” stopped us all dead in our tracks followed by someone else asking, “So how do you get a skunk out of a trap without getting sprayed?!”  With great trepidation and a lot of ingenuity as it turns out.

Have-a-Heart Traps are tricky.  To release an animal and reset the trap, there’s a lever at the top that needs to be pulled back and held back, a ring that needs to be released from the front, and a flat panel that needs to be shoved forward into the trap until it snaps in place.  Trying to manipulate all three would bring us within squirting distance of the skunk.  Hmmm.  So how do we do all three at a distance?

We first determined that we had to move the trap out farther into the yard.  We threaded a 15 foot piece of PVC through the handle on the top so that two of us could swing the trap away from the fence line and into the yard.  Easy.  Until we realized that a corner of the trap had snagged on a trailing edge of the netting that covers the chicken run.  Jiggling the trap to untangle the netting did little more than rouse the skunk who stood up, arched his back, raised his tail and fixed his earnest gaze on the nearest jiggler.  That put a stop to that!

One of us went into the chicken run to try to pull the netting free.  But as we tugged, we nearly upset the trap (and the skunk!)  We discovered the skunk had begun building a nest by gathering grasses and the netting and dragging them through the steel mesh into the trap.  It seemed a cozy nest, and we were sorry to have disturbed his sleep, but we had to evict him.  After carefully drawing the net back out of the trap, we swung the trap into the yard and hastily covered all but the front of the trap with a tarp.

Whew! We breathed a sigh of relief.  It seems that just like the smaller mammals, we were, on some lower mammalian level of our own, working on the premise  that what you can’t see can’t hurt you.  In this case, it may be true.  We all, the skunk included, seemed a little less tense, and the rescuers could set about their work with less trepidation.

There’s an old maxim, “Always use the right tool for the right job.”  Well, at-a-distance-skunk-releasing-tools aren’t the run of the mill tools we usually have on hand at the farm.  The next best thing is to improvise.  Here’s where the ingenuity comes in.  Ingenuity means standing in the barn and seeing what you have to convert into the right tool for the right job. It means seeing the qualities of something and their application in the broadest context and seeing if those qualities overlap with the qualities needed to address the current issue.  In this case we found:  a 15 foot length of rope, a 10 foot piece of thick wire used to make cover cloth hoops,  a 15 foot piece of 2” bamboo, a garden hoe, and duct tape.  With these handy supplies, we could construct the necessary implements to effect the skunk’s release at a distance.

The metal wire was bent in half to form an open loop at one end; this would be used to pul back the lever.  The hoe was duct taped to the bamboo pole resulting in a 20 foot long lever depressor.  The rope would be attached to the release ring at the front of the cage by some courageous soul .  We all took our places, and after the rope had been attached to the front ring, on the count of three we, yanked, pulled, and pushed and then ran away!

It only took a few moments for our unintentional captive to make a dash for the closest  cover—the old overturned rowboat.  He huddled in the weeds at the base of the wall and extended his clever little paws up and up until he found a section of the wall low enough for him to clamber up and over .  In an instant, he had scurried under the rowboat to safety.

What would we have done had the skunk actually sprayed us?  Applied Skunk Smell Remover.  As it turns out, tomato juice doesn’t actually eliminate skunk odor, it simply disguises it.  Wash off the tomato juice, and the stench of skunk remains!  To be rid of skunk smell, you have to create a chemical reaction that will break the bond between the sulfer molecule in the skunk smell and the oxygen molecule in the proteins that make up whatever has been contaminated.  The following recipe works wonders!  How do we know?  Some of us have had to use it!

 Skunk Smell Remover

 1 qt. of 3% hydrogen peroxide

¼ to ½ cups baking soda

1 – 2 tsp. dish soap

1.   Mix hydrogen peroxide, baking soda and dish soap.

2.   Wet the smelly object or surface with warm water.

3.   Liberally douse the offending object, person, dog, etc. with the Remover.  Rub in  thoroughly.  (Rubber gloves might be a good idea!)

4.  Leave the skunk odor remover on for 5 – 10 minutes so it can set, rinse thoroughly, and then repeat this process as necessary.

It’s important not to store this in a closed container since the mixture of these ingredients creates pressure and could burst.  The solution’s effectiveness also diminishes very rapidly.

The addition of dish soap is important; the soap contains the surfactants that will encase and wash away the smelly molecules that the Remover has released through the breaking of the chemical bond.  Fancy smelling soaps are a bonus!


It’s hot! But no drought … not quite, not yet.

Not us! Not yet.

“Crunchy” is not an adjective that one usually wants to apply to one’s lawn.  But that’s precisely what the grass is this blazing, thirsty July … crunchy.   And yet, according to the weather service, we’re not in a drought.  Well, that all depends on how you define a drought, now doesn’t it?  What’s a drought?

Hydrologic drought is when the groundwater aquifers, reservoirs, and stream flow are below normal. The massive snows of this past winter recharged the aquifers and while the stream flow for the Christiana River is running between the 24th and 74th percentiles (See http://md.water.usgs.gov/surfacewater/streamflow/christina.html ) this is still normal for this time of year on average.  In addition, the large, established trees that rely on subsurface water tables seem in good shape, their leaves full and plentiful. (See http://www.drought.unl.edu/vegdri/VegDRI_Main.htm)  So, accordingly, there’s no drought by these measures, close maybe, but not yet.

A meteorological drought is defined as “a period of abnormally dry weather sufficient to cause a serious hydrological balance.” (Huschke, R.E., ed., 1959, Glossary of meteorology: Boston, American Meteorological Society, 638 p.)  This can be variously defined as an “absolute drought”, a “partial drought”, or a “dry spell”.  An absolute drought is a period of at least 15 consecutive days with less than 0.01 inches of rain or more on any given day. A partial drought is a period of at least 29 consecutive days, the mean daily rainfall of which does not exceed 0.01 inches. A dry spell is a period of at least 15 consecutive days with less than 0.04 inches or more on any given day. If we check the monthly rainfall for June and July, we’ll discover that, meteorologically speaking, we’re not only not in a drought, we’re not even in a dry spell!

But from a farmer’s (or lawn owner’s!)  perspective, it’s quite another thing.  A more recent delineation of the different types of drought includes “agricultural drought”.    Agricultural drought isA climatic excursion involving a shortage of precipitation sufficient to adversely affect crop production or range production.” (Rosenberg, N.J., ed., 1979, Drought in the Great Plains–Research on impacts and strategies: Proceedings of the Workshop on Research in Great Plains Drought Management Strategies, University of Nebraska, Lincoln, March 26-28: Littleton, Colorado, Water Resources Publications, 225 p.) Agricultural drought occurs when there isn’t enough soil moisture to meet the needs of a particular crop at a particular time. Agricultural drought happens after meteorological drought but before hydrological drought. (From: http://www.drought.unl.edu/whatis/define.htm )

Yep. Our crops and your grass have definitely been adversely affected.  Sounds like a drought to me!

For the farmer, the difficulties are threefold:  too much warmth too soon, too little or inconsistent, intermittent rain, and too much sun. Warmer than normal temperatures with abundant rain early in the growing season cause plants to put forth lots of top foliage before they are ready to flower.  If the rain shuts off later in the season as the blossoms are becoming fruits, then the plant struggles to maintain the greenery it initially grew to the detriment of the fruits we look forward to eating.  Warmer than normal temperatures encourage abundant growth, but too much sun, and the tender leaves burn resulting in the loss of entire crops of tender leafy green crops: lettuces, spinaches, etc. and the damaging of newly germinated seedlings.  In fact, sometimes the seeds themselves bake in the too warm soil and never germinate at all.  Rain could to some degree help, but without it, there isn’t much we can do for the seeds already planted. That’s one reason why we do multiple plantings over time of the various crops and have plenty of additional seed on hand.  It’s not a cure-all, but it does mitigate the effects of the drought IF it doesn’t last too long!

So what do we do?  Well, last year we could  water, and did water, sometimes three times a day. The plants were thirsty, and we were glad to do it. Early in the morning, in the evening, and sometimes even in the dark!  With watering cans in hand we walked along the rows, becoming cloudy, indistinct forms after sunset.  There’s something very fairy tale like about watering by moonlight while the deer roam nearby in the hush of the night.

But this year, this crunchy July, we’re giving up our water cans for drip irrigation.  Hooray!  More on that in our next newsletter.

The Circus Comes to Town!

Aeronautical acrobats and high wire acts

Birds abound at the farm.  Barn swallows, bluebirds, a red wing blackbird, and 2 pairs of goldfinches flash amongst the more subdued colors of crows and grackles and mourning doves.  We’ve discovered another denizen recently, a hummingbird.

Thera was walking out by the tomato trellises when she noticed two birds sitting on the topmost trellis bar.  One was a fairly large songbird, the other a tiny fellow only a quarter the size.  She wondered what it could be until it rose into the air and began the hover, flit, hover, flit dance so definitively hummingbirdesque.  What a delight! Now we get to watch the hummingbird two-step in addition to the swallows’ waltz!

Occasionally our bird friends pass from the sublime into the comical.  And once again the trellises are involved.  The metal tubing that forms the frame of the trellis is a handy and sturdy perch.  The twine that the vines clamber up, is not.  The birds haven’t quite figured that out.

For whatever reason, the birds will try to perch on the netting, and will not give up, even when the harmonic motion sets in.  And so … A bird lands on the twine.  Whoops! The twine sinks away under his slight weight.  To the bird, it’s a simple matter of adjusting his balance by flapping his wings – it works with tree branches, it ought to work here – or so instinct says.  But the twine, unlike a tree branch, is not anchored to anything as unmovable as a tree trunk; it’s attached to another equally moveable bit of twine. And that’s when the high wire act begins. Gripping the twine, finding himself unsteady, he flaps his wings to balance himself, setting the twine in motion, which makes the little fellow flap all the harder, which makes the twine swing all the more wildly so that he flaps more wildly… back and forth, faster and faster, he swings and balances and will not let go!  Eventually, sometimes, he succeeds; the twine’s arc is the obverse of his wings’, and bliss! All is still. But, add a second and a third and a fourth bird, and the farce truly begins.  For as one little fellow gains his balance, another has not, and in trying to correct himself, sets everyone else into fluttering, clutching, swaying, and flapping.  No circus clown or tight rope walker was ever so amusing!

Braconid Wasps versus Tomato Hornworms

          Ah, tomatoes.  We’ve harvested the first of the season.  How plump, how juicy, how tasty!  With such bounty in the offing, we look down the long days of summer with delight.  But there’s a kink in our path, a stumbling block, a veritable bug in the program, you might say.  Tomato hornworms. Neon green and gaudily stripped and dotted, these voracious destroyers can grow to an enormous size and devour an entire tomato plant in a day or two if not stopped.  What to do?  We go on hornworm hunts.  Dawn and dusk are best when they aren’t hiding under the greenery away from the blazing sun, but hornworms, for all their great size, can be elusive, and the hunt time-consuming.  Fortunately, we have allies.

In sustainable agriculture, we use the most natural methods of pest control that we can.  One of these is to encourage natural predators to take up residence in our fields so that they can eradicate those pests that they find tasty and we’d rather be gone.  A good example are ladybugs whose favorite food are the aphids that suck the juices from plant stems. We are now fortunate that braconid wasps have been making their appearance among the tomatoes.

There are three kinds of parasitism in the natural world:  predators, parasites, and parasitoids.  We’re familiar with predators: foxes, hawks, ladybugs. Usually larger than their prey (on the farming, not the Africa veldt scale!), they eat many individuals over the course of their lives.  We’ve also heard about parasites which live in (or on) a single host their entire life, occasionally debilitating, but rarely killing it.  And then there are the parasitoids.  These are the ‘predators’ that seem most alien to us. A parasitoid spends only a portion of its life in or on a host, using the host for food, and in the process, killing it.  Even the definition can give one the shivers!

Braconid Wasp drawing from Pacific Horticulture

Braconid wasps, small black wasps with transparent wings that are rarely over a 1/2 inch long, are parasitoid.  The adult wasp lays her eggs just under the skin of the tomato hornworm, and while the hornworm is munching along on the tomato leaves, the wasp larvae are eating the worm alive from the inside out!  The larvae once ready to become wasps, burrow out from under the hornworms skin and spin cocoons where they pupate until ready to emerge as full-grown wasps.  Usually, only then, does the tomato hornworm expire.  It’s a long, and to human sensibilities, a gruesome demise, but for the braconids and hornworms, it’s the way nature works.

One of the drawbacks of relying on parasitoids to protect crops is that it is a long-term solution.  It may take a year or two for braconid wasp colonies to have grown in sufficient numbers to adequately control the hornworms, and until then our crops are in danger.  So while we will leave a braconid-infested hornworm alone to suffer its fate, we still pick off and feed the others to the chickens.  In sustainable agriculture, we use a mix of approaches; in the end, we and the wasps will win.

For more on braconid wasps, see: http://www.pacifichorticulture.org/garden-allies/69/2/


3rd Year Experiment: Trellises

We do a lot of “experimenting” on the farm. What will be more efficient?  What increases the health and productivity of our crops?  What have others tried?  What’s worked or not, and why?  We’re always trying something new (or old, as the case may be with sustainable farming.)

There has been an addition to the landscape at the farm – trellises.  Many plants benefit from trellising: peas, beans, tomatoes, cucumbers, melons, and peppers to name a few.  Any plant with a vine like stalk can be trellised. Trellising is also good for humans; it takes up less room for those with smaller yards and an urge to garden, and it makes picking the fruits a little easier on the knees and back!

Bamboo Trellis

This is our third foray in trellising.  Our first experiment was based on one that we read about in a book by Shepherd Ogden.  He recommended using lengths of bamboo leaned against and tied to each other, to make a sort of elongated tee-pee, with twine tied into a net.  We chose to do this because we had a free supply of bamboo from a friend’s backyard.  We grew beans on these. They were picturesque and worked well until about two-thirds of the way through the season.  The trellises started to collapse because they were rotting through in places.  While wondering why that might happen, we noticed that Mr. Ogden resides in Maine, where the growing season is cooler, dryer, and much shorter – and we live in the middle of a swamp.  As with so many things about farming, moisture is key!

T post and Twine

We used a second variety of trellising for tomatoes last year.  This approach was one that Thera had used on a farm on which she had interned.  In this version, t-posts were spaced every few plants, and twine was tied horizontally between the posts on both sides of the plant to support it by sandwiching it between the strands of twine.  That worked, but required frequent attention: the addition of more twine, the tightening of old twine, and the weaving of errant tomato vines between the strands.

We’re trying this year’s design, which we hope will be an improvement, because it should last for many years, and be much easier to maintain. Each trellis is composed of two 4′ pieces of rebar, two 10′ pieces of ½” EMT electrical conduit, bent into shape, a 5′ piece of ½” EMT electrical conduit, and two set-screw couplings (to join the 5′ piece to the two 10′ pieces), and twine.

As with all new approaches, we sometimes have to learn as we go. To make the trellis frames, we used a conduit bender, a “cut-off saw,” and a metal grinder.  We thought it would be an easy matter to fit the conduit over the rebar, but were frustrated in this when we discovered rebar often has a burr at the point at which it was cut.  About half the pieces of rebar couldn’t be used, and the other half had to have the conduit forced over them.  To respond to this, we borrowed a grinder, to grind the burr off one end of each piece of rebar, and now the conduit fits neatly over just about every piece of rebar.

Two stem, Vertical Twine Trellis

Once the plants are sufficiently mature, a piece of twine will be looped over the plant, wound around the main stem, and tied to the conduit above.  Each plant will be trimmed back to one or two main growing stems which will climb up this single line of twine.  It’s very exciting to see what will result!

For more on how to trellis various types of plants, see: http://www.gardenguides.com/79086-vegetables-can-grown-trellis.html

From E, I , E, I …OH!   the Omnia Humanitas Farm Newsletter

vol 3 issue 2  / June 2011