Looking Over Clover

To any person who has spent enough time sitting on a patch of lawn to get a little bored, the leaf in the picture below will be instantly familiar. 

One clover leaf.

It's a leaf of the white clover plant, and there is plenty of it at out outdoor classroom right now.  One clover leaf has three parts, which is reflected in the Latin name of the plant: Trifolium repens.  Tri- means three, and folium means leaf.  Repens means reclining, which this plant does well, as it spends its entire life within about 3 inches of the ground.  Clover leaves usually have faint white lines in them, and they are never heart-shaped.  Another common lawn plant called oxalis has leaves divided into three heart shapes, and sometimes people get confused about it.

A patch of clover.  See any lucky ones?

White clover has several claims to fame.  First, they are tough little plants, and they survive well on lawns even under heavy foot traffic, so they grow everywhere there is a lawn.  People who are sticklers for uniform-looking lawns consider the plant a weed, but many people value the plant for its ability to grow in harsh conditions where grass can't grow.  Second, clovers are known and loved for their sweet-smelling flowers, which are white or pinkish clusters on stems.  I bet you have made a flower chain from clovers before.  Bees love the flowers even more than humans do, and they make great honey from it.  The sight of clover flowers on a lawn should serve as a warning to wear shoes, since bees are likely to be on the flowers, and stepping on a bee will get you stung.  Clover's third well-known benefit is its value as a food source for animals.  Clover seed is often included in the mix of seeds farmers plant for growing cattle forage (the plants cattle eat).

A small clover plant with leaves, stems and roots.

Clover also has a secret.  Most people don't know much about the hidden power that makes clover so important in nature and explains some of its better-known characteristics.  If you dig up a small clover plant and look at the roots, you see something that is not usually present on plant roots: tiny lumps.  Those lumps are called nodules, and they are actually little areas where clover keeps its own pet bacteria.  The clover provides food and housing (and maybe even affection) to the bacteria in return for the services the bacteria provides to the clover.  The bacteria produce an otherwise almost unobtainable nutrient called nitrogen.  Nitrogen is a nutrient used to make protein - the microscopic parts of organisms that provide much of their actual structure as well as much of the machinery to conduct life's processes.  Other plants can only get nitrogen by absorbing leftover nitrogen from dead clover-type plants or from decomposing animals or animal manure, but clover has its own constant supply.

Root nodules on a clover - where nitrogen is fixed.

Clover's source of nitrogen means it can grow on poor soil where grass can't.  It also means it has a high nitrogen content, making it more nutritious than grass for animals to eat.  When clovers die, they leave behind richer soil with more nitrogen, where other plants can now grow.

Clover is related to bean-type plants (pinto beans, Limas, black beans, lentils, peas), and all types of bean plants have the same pet bacteria for making nitrogen (actually called fixing nitrogen).  This type of interaction between two organisms that live in close contact and help each other is called mutualism.   Can you think of other examples of mutualisms?

Have you ever found a four-leaf clover?  Sometimes the plant makes an error when growing its leaves, resulting in our four-leaf symbol of good luck.  If you look at a patch of clover for long enough, you will probably find a four-leaf clover.  If you do, press it flat between pages of a book for a week or so, then you can glue it to paper or press it between clear tape to preserve it.

Why Don't Fish Need Mittens?

Brrrr!  It's been cold the last few nights!  Air temperatures dropped into the mid 20's, which is way lower than freezing.  I bundled up in many layers to survive being outside for about an hour last evening.  I felt a little bad for the fish in our outdoor classroom - they are stuck in cold water without any hats or mittens or even hot cocoa to warm them up.

A mosquitofish alive and well after several nights of freezing temperatures.

Humans are like tropical animals in terms of their thermal comfort zone.  We are comfortable living in temperatures in the 60's to 90's on the Fahrenheit scale.  We have created many devices to keep ourselves at a comfortable temperature: clothes, buildings, heat, air conditioning, insulation and ice cubes all help us maintain comfortable body temperatures whether we are in the tropics or in the Arctic.  Animals can be classified as endotherms or ectotherms, and we are of the endotherm variety.  Endotherms use some of the energy in the food they eat to keep their bodies warm.  Even though the temperature of the air inside our buildings is usually around 72 degrees, our bodies stay at 98.6 degrees.  Mammals, birds and even some fish like tuna can keep their body temperature warm using energy from food.

Mosquitofish are happy as clams in a much broader range of temperatures than we can stand.  They can live in the very warm water of shallow sunny pools in the summer, and they can survive a fairly cold winter too.  Mosquitofish are ectotherms, like most fish, amphibians, reptiles, insects and mollusks.  They don't keep their body temperature warm - they let it cool off when the environment cools off.  And as the temperature drops, they simply slow down.  Their bodies move more slowly, they eat less food, and they stay more hidden.  Many ectotherms hibernate, essentially sleeping in a cold state until the weather becomes warm enough to move around again.  If you watch our mosquitofish, you will notice that they are much slower on cold days than warm days. 

Mosquitofish can't survive if the pond freezes all they way through.  Fortunately for them, water temperature usually doesn't get as low as air temperature, so the pond is going to be warmer than the air temperature, and it won't usually freeze.  Also, ponds freeze at their surface, then the ice acts as an insulator, keeping the lower layer of the pond from freezing.  So even if you see ice on our pond this winter, it is likely that the mosquitofish will be swimming slowly in the water under the surface. 

Do mosquitofish feel cold?  I don't know.  I suppose you would have to put a mosquitofish in a fish tank with a cold area and a warm area and see where it chooses to spend its time!

Here are some other ways you can see organisms responding to the temperature at the outdoor classroom this week:

It's easy to see which plants survive freezing right now.  I'll write about this more in the deep winter, but it's probably easier to see now before the dead plants blow away and decompose.  The dead leaves in the picture below didn't survive freezing.  Either their seeds will survive the winter or their roots will survive in the ground, but it will not grow again until the spring.  The plant on the left is just fine with freezing temperatures, and it will stay growing, though very slowly, through the winter.  there are lots of winter-growing plants in our classroom.

The fern on the left survived freezing, the plant on the right did not.

The honey bees are still drinking at our pond on warm days!  They must have a fairly warm location for their hive.  Bees do some temperature regulation of their hives by eating food then shaking their wings really hard inside the hive to generate heat.  Our bodies do a similar thing - they shiver to generate heat.  Bees also flap their wings to fan the hive if it gets too hot.  Even though insects are ectotherms, bees have some endotherm ability.  Neat!

Honey bees are still drinking from our pond on warmer days despite the freezing nights.

Tube Flowers and Their Pollinators

Butterfly bushes (Buddleja sp.) are very well-named.  The ones in our outdoor classroom are usually surrounded by several butterflies flying from flower to flower and filling their butterfly bellies with nectar.  If you look closer, you'll notice that lots of types insects like butterfly bush nectar, and even hummingbirds have been known to drink from these flowers.  Because of the shape of butterfly bush flowers, not all nectar-feeders are able to use these plants.  All butterfly-bush-feeders must have long, thin mouthparts that fit into the flowers.  Notice the long curved proboscis on the skipper in the photo below.  The proboscis works like a silly straw, curving and extending into the base of each flower for a sip of nectar.

A skipper sipping nectar on a butterfly bush.

Below you can see one individual flower of the butterfly bush.  The green bit is the base of the flower where nectar is produced.  The purple petals form a tube that opens at the top of the flower.  The tube shape does a good job of keeping out insects that steal nectar without pollinating the flower.  Insects that can reach their mouthparts into the flower receive a dusting of pollen as they sip nectar.  When the insects move to the next flower, they drop off the pollen, allowing the flower to produce seeds.  Nectar-sippers and flowers have a trade-off where each organism benefits from the arrangement: flowers are pollinated and the pollinators get food.  This relationship is called a mutualism, and it is a type of symbiosis where two organisms benefit from the interaction.

A single tube-shaped flower of the butterfly bush.

The purple tube-shaped flowers have orange centers to help insects find their way into parts of the flower where the nectar is produced.  Most flowers have nectar guides in their centers.  Usually nectar guides are yellow or orange regions with lines pointing to the center of the flower.  Next time you are at the outdoor classroom, look for nectar guides in butterfly bush flowers and any other flowers you'll see.

Yellow/orange nectar guide inside a butterfly bush flower.

Below you can see two more organisms that are mutualists with butterfly bushes: bees and longhorn beetles.  Both pollinate the flowers and get fed in the process.  There are some insects that 'cheat' the butterfly bushes out of their pollen.  Some types of caterpillars, beetles and ants chew through the base of the flower, drink the nectar, and leave without pollinating the flower.  Look carefully at our butterfly bush flowers for some crime-scene evidence:  if you see holes chewed through the base of their tubes, you know the nectar has been stolen with no pollination payment in return!

Bumblebee and longhorn beetle working the butterfly bush flowers.

Interesting side not:  The bumblebee in the photo above was not actively feeding.  It was just holding on and resting.  This time of year, the temperatures are dropping, and insects that don't overwinter are nearing the end of their lifespan.  It could be that this bee is slowing down because it is old.  Alternately, the bee could be finding its home for the night, since I took this photo in the early evening.  Bumblebees often sleep in large flowers or near small flowers so they have a food source in the morning (wouldn't you love to sleep in a flower?).  A third possibility is that the bee is just slow because the temperature is lower.  Some bees just slow down when the temperature drops, stay in a torpor through the cold winter, and then speed back up again in the summer when it's warm.

Drinking Bees

The waterfall at our outdoor classroom attracts more than just people.  It's the ideal place for some insects to stop for a drink.  There must be a honeybee hive somewhere near the school, because our waterfall has become a bee watering hole!

Honeybee drinking water on an algae-coated rock.

Honeybees are my #1 top favorite insect, which is ironic since I was scared of them as a child.  Once I learned about them, I grew to love them best of all.  Not only do honeybees make honey to feed their offspring and feed themselves, but while they are collecting nectar to make the honey, they pollinate flowers.  Most of our agricultural crops need to be pollinated by insects, and honeybees are the best pollinators.  Honeybees are so helpful to humans that farmers often have honeybee hives on their farms to make sure their crops are pollinated.  If you like nuts, berries, apples, cherries, squash, tomatoes or avocados, thank the bees for making them possible.  I love to think of our pond as helping the bees.

Honeybees drinking on our waterfall.

We've all seen bees pollinating flowers, but I bet few of us have been able to watch honeybees drinking.  A good, clean water resource is incredibly valuable to bees, especially in the city where water is hard to find.  Bee keepers make sure their bees have access to clean water, or they provide water dishes to their bees.  Bees, like all creatures, need to drink water.  The bees use the water to make the fluids in their bodies, and they also sweat like we do to keep their bodies cool.  Bees carry water back to their hives to help keep the hives cool and to dilute the honey to feed their larvae.  Bees fan wet surfaces in their hives with their wings, causing the water to evaporate, which cools the wet surface and the hive.  You can observe this phenomenon if you dangle a wet towel in front of a fan. 

The top level of wet rocks is safest for bees to drink from.

Water is a tricky substance for small creatures like bees to deal with.  It might be strange to think about, but water is sticky to most surfaces.  In fact it's so sticky, that you have to use a towel to get it off of yourself after you shower.  The more surface something has, the more water sticks to it.  Think of how difficult it is to dry your hair, which has millions of surfaces all packed together, compared to drying your skin, which is one surface.  The stickiness of water is both helpful and dangerous to bees.

The good part about the stickiness of water for bees is that it's easy for bee mouth parts to soak up water.  Bees have a feathery tongue that sticks to water like hair does.  The bee just has to touch its tongue to water, and water wicks into it.  You can see the phenomenon of wicking if you touch the edge of a paper towel to water and watch how the water climbs further on to the paper towel.  Paper towels that are thicker with more microscopic fibers to provide more surface wick better than thin, smooth paper towels.  Bee's feathery tongues have lots of surface and are good wickers.   You can see a bee tongue sipping nectar on the flower from my garden in the picture below, but the picture is not magnified enough to tell that the tongue is feathery.

Honeybee soaking up nectar and pollinating chive flowers.  Note battered wing and pollen sack.

The dangerous part about water's stickiness is that bees' bodies can easily get stuck to open water.  If a bee lands on the surface of the pond, its body will stick and it won't be strong enough to get unstuck from the water.  The bee will likely drown unless someone scoops it out and sets it on dry land (careful - it will likely be stressed and possibly sting if you use your hand to do this).  To protect themselves, bees must stand on hard surface and drink from water that has seeped onto the surface.  Leaves and sticks on the surface of a pond are good platforms for bees to drink from.  The rocks in our waterfall are perfect surfaces from which bees can safely soak up water.

Surprises of Fall

Fall came so quickly this year.  Today is the first day of fall, but we have had fall weather for the past several weeks.  Spending entire days every week interacting with the earth and plants has made me notice the season's changes much more acutely this year.  Here are the things I've noticed most as the weather has changed:

• The bees and wasps are already gone.  The flowers are still going strong, but that cloud of buzzing has disappeared.  There are still a few slow bumblebees here and there. 
• The spiders are out in force.  Many blooms have their own resident flower spider, and there are lots of webs strung up between the plants.  We had the biggest garden spider I've ever seen in the hoop house. 
  

  

  Garden Spider Source
  

• It feels strange to eat cherry tomatoes when it's cool and cloudy.  The tomatoes taste the same, it's just not as heavenly to pop them in my mouth when I walk by the tomatoes.  Now I want to nibble the turnip leaves.
• The smell of tomatoes rotting in the field is almost intoxicating.  It's difficult to describe why this is so wonderful, but there's a toasty, dusty, cheesy, roasted tomato smell all around the tomato rows from the unusable tomatoes that makes my head spin.  Rotting squash smell great in the field too.  Don't try this at home - it doesn't work without sunshine and dirt.
• The crops are all different now.  Instead of tomatoes, squash and melons, we have turnips (the best vegetable), chard and beets.  It happened so fast.
• The weeds have slowed down a lot, thank goodness.  Even though I can see the scattered crab grass seeds everywhere, and I know what's ahead for next summer, the pressure's backed off a bit for now.
• It's easy to get a LOT done now that it's not 100 degrees.  In the extreme heat, work slows down due to the body's physiological constraints.  These crisp, cool days mean that I can work fast and easily, and everything feels good.
• I only go fill my water bottle once or twice a day now, instead of four or five times.
• Ironically, the work is starting to taper off even as our capacity to do it increases.  Since fewer crops grow during the winter, a lot of the fields are lying fallow, and we have planted cover crops.  Here is the melon field, all disked in and planted with a mixture of vetch, radish and rye for the winter:

  

  This field is done for the year.
  

• The farm is looking more neat and tidy.  With things growing more slowly, there is time to organize and clean up.  June and July felt like a race to keep up with the creeping jungle of crops and weeds, and now it feels like we are getting ahead.

I only have one or two more days to work on the farm, then I'm moving to the heart of Chicago for a while.  I expect the contrast to be a little jarring.  I'll be reporting on what biological phenomena I observe in the city.  In the mean time, I'm savoring the last few hours of fresh air, big skies and working on the earth here in Middle Tennessee. 

Bug Beds

Imagine you are an insect, and the nights are getting colder.  You don't really have a home to go to, but you need a place to snuggle in to survive the cooler nights.  There are a million places you could go.  You could hang under a leaf or sit on a tomato flower, but the real Ritz-Carlton of the insect world is the celosia flower, seen here.

Celosia

Celosias are gigantic, fuzzy, and filled with little crevices to lodge for the night.   There is even breakfast in bed for their guests, because the flowers provide plentiful nectar for bees, wasps and other insects.  I imagine it must be very pleasurable to settle in to these soft, velvety flowers.

Hive-less, or solitary bees will often nestle into or under a flower to get through the night.  If you go into your garden very early in the morning, you will undoubtedly find some sleepy bumble bees or wasps curled up inside your squash flowers or daisies.  If the morning is cool, you can even touch the bees - they will be too cold to panic. 

This week, we had an exceptionally cool day.  It was 95 degrees one day and 60 the next.  The bees and wasps (and the rest of us) were caught off guard, and they didn't leave their flowers for the entire day.  As I harvested celosias, I noticed bumble bees, cicada killer wasps, ichneumon wasps and many other wasps and bees sitting inactive amongst the celosia blooms.  I could get as close to them as I wished without disturbing them.  Unfortunately it was also raining, so I didn't get pictures.  You'll have to make do with this picture of a cart loaded with gorgeous celosias that I harvested. 

Cart of celosias

Not All That Buzzes is Black and Gold

The airspace on the farm is busy.  There is no air traffic control, but no one seems to collide.  I'm a giant lumbering along amongst the cloud of busy insects as I work my way down rows of flowers and vegetables.  They hardly seem to notice me as they go about their work.  With so much time and so many insects, I've gotten to know their sounds well.  You can tell an amazing number of buzzing insects by the qualities of their buzzes.

The easiest to recognize are the cicada killer wasps I wrote about a few weeks ago (here).  They have a steady bass tone - a low buzz in which you can occasionally hear individual wing beats.  They are loud and their pitch only changes from the Doppler Effect, lowering a bit as they fly away.

Cicada killer wasp.  Picture source.

Bumblebees are the most common on rows of flowers.  Their buzzing is all fits and starts as they whiz from one flower to the next.  They seem to have trouble steering because they swerve around a flower's entrance before crawling onto it, so their pitch varies widely as they try to align themselves for landing. They are generally loud and low in pitch.

Bumblebee.  Picture source.

Honeybees are quiet and unfortunately rare on the farm.  They move and sound a lot like quiet, higher-pitched bumblebees.  If bumblebees are the bases, honeybees are the tenors.  Sweat bees are the sopranos.  They have these little tiny, quiet buzzes as they try to wedge themselves into the backs of your knees so they can sting you when you squat down.  They are usually unnervingly near you, and they whiz off when you try to swat them.

Sweat bee.  Picture source.

The bugs, stink bugs and assassin bugs, are hilarious once you get used to them.  They buzz so stereotypically that I expect them to have little captions over their heads filled with z's.   They hide amongst the green parts of plants instead of the flowers, and they wait until the last minute to try to escape from a perceived threat.  I'll be harvesting tomatoes and all of a sudden a loud buzzing bug will be flying erratically very near by.  No other buzzing insect buzzes so close and loud. 

 

 

 

Leaf footed bug.  Picture source.

There are some stealth insects too.  Wasps usually don't make a sound.  If you are very quiet, you can hear a little purring noise when they are very close, but usually they just seem to float by noiselessly.

Paper wasp.  Picture source.

Birds Do It, Bees Do It........Even Zucchinis Do It

I am the only person in the world who seems to have trouble growing zucchini.  They are notoriously generous in fruit, and you always here gardeners joke about being overwhelmed by their zucchini crops. There are even stories about gardeners secretly dropping of baskets of zucchinis at their neighbors' houses just to get rid of them.

I've gotten better at growing zucchini plants through the years, but still have little luck with the actual fruits.  (Yes, they're fruits, according to the botanical definition.  Any plant part that contains seeds is a fruit.  Don't worry - I call them vegetables when I'm cooking.)  My home garden has a lot of shade for a garden, and my first few years of planting zucchini in the shadier regions allowed the plants to be overcome by a dusty white mildew.  Any zucchinis would wither and rot before they grew two inches.  Now my plant is in the sunniest patch I have, and it's healthy, but my zucchinis are still withering prematurely.  Here is this year's zucchini plant, recovered from the hail damage:

After talking with the farm owner where I'm working this summer, we agreed it might be a pollination problem.  Pollination is how plants reproduce, and seeds and fruits are the offspring of plant reproduction.  Pollen, is the plant equivalent of sperm, and it must reach the botanical equivalent of eggs, called ovules, for seeds and fruits to develop.  There seem to be two possible pollination problems in my case:  maybe there aren't enough bees to pollinate the flowers; or maybe there must be two plants for successful pollination.

Option 1, not having enough bees, is a distinct possibility.  There aren't many bees in my neighborhood.  I do see bumble bees, but they tend to cluster out front where all my ornamental flowers are.  I have seen no honey bees this year, which I fear is due to colony collapse disorder - see a future post on this.  To remedy this problem, I could plant some bee-attracting plants near my zucchinis so there is more of a reason for the bees to fly all the way over there.  I could also start a honeybee hive in my back yard, which I will do some day if my neighbors aren't reading this blog.  Or, I could hand-pollinate the flowers when they open every morning, which is what I have been trying.

To hand-pollinate the flowers, you must understand a little about the reproductive organs of zucchini plants.  Flowers are always reproductive organs for plants, but each type of plant is a little different.  Zucchinis and all squash-type plants produce separate male and female flowers.  Most types of plants have male and female in the same flower, but some may have entirely separate male plants with only male flowers and also female plants.  Hollies have separate genders, which is why only some hollies grow berries - only females can grow fruits and only males can produce pollen.

On zucchinis, the female flowers grow out of what looks like tiny immature zucchinis.  This organ is the female flower's ovary, and it is filled with ovules.  The ovary will one day actually become a zucchini, and the ovules will become seeds after the flower is pollinated.  Notice the thick regions behind the female flowers below - they are ovaries.

Male flowers have a normal stalk, and inside the male flowers are pollen-producing organs called anthers.  Here is a male flower:

For pollination to occur, the pollen must be transferred to sticky pads, called stigmas, inside the female flower.  Each pollen grain then produces two actual sperm cells that burrow down through the flower to an ovule and fertilize it.  Many pollen grains are needed to fertilize all those ovules inside a zucchini ovary.  When the ovules are fertilized, the fruit begins to enlarge and grow into a mature zucchini with mature seeds.  If no pollen is transferred, or only a little is transferred, there is no signal to the plant to grow the fruit, and the ovary just withers and rots like mine have been doing. 

I have been hand-pollinating for a couple of days now, by touching my finger to the anthers in the male flowers and smearing the pollen on the female flowers.  I think it may have worked!  Here you see the stigmas inside of a female flower and what I think may grow into an actual zucchini:

Regarding the second possible pollination problem, I may have to plant two zucchini plants next year.  Since I only have one zucchini plant, the pollen I used came from the same parent plant as the flower I transferred it to.  Some plants don't mind reproducing with themselves, but zucchinis may be somewhat pickier.  The zucchini that seems to be growing could have been pollinated by pollen from a neighbors plant.

On the farm, the year they had a bee hive, the squashes were much more productive, since all their flowers were being pollinated.  It really makes you appreciate the bees more when they are not there to do that garden task for us.