Nandina: A Berry Interesting Problem

Oh, nandina, nandina, you trouble my heart!  You are so beautiful all winter with your green foliage and bright red berries, but you are an invasive plant.  What is a good naturalist to do?

Nandina, AKA heavenly bamboo.

Invasive species (species = type of organism) are a problem in Tennessee, and in the rest of the world as well.  They are currently the #2 cause of extinction of other species, just after habitat destruction.   Invasive species are non-native organisms that grow like crazy and take over.  Non-native organisms are moved from one part of the world to another, mostly by humans.  This is usually not a problem, except that for some non-native species, the new habitat has none of their usual diseases and predators, and the habitat seems to fit just right.  In that case....they can take over and crowd out the habitat of other organisms.  Nandina is native in Asia - from Japan west to India.  It is a beloved plant there, also used in landscaping like we use it here. 

Poisonous beauty: these berries contain nandina seeds and cyanide!

In Tennessee, some of our most harmful invasives are bush honeysuckle and kudzu.  Bush honeysuckle uses up habitat for other plants.  Also, birds that nest in it are more likely to get eaten (not sure why).  Kudzu simply crowds out every living organism where it grows.  Nandina is not that bad!  It is usually only found growing wild near where humans have intentionally planted it.  The Tennessee organization that helps keep invasive plants under control (TN-EPPC)  wants more information about nandina in order to keep tabs on the problem.  If you are ever out hiking in the wild (not in a landscaped yard) and you see a nandina, TN-EPPC would like to know about it.  You can report an escaped nandina at the TN-EPPC website: http://www.tneppc.org/

A nandina draws your gaze from behind a sedimentary rock.

Biologists worry about invasive species because they cause the total number of species to decrease.  The loss of a species, or extinction, causes the loss of a participant in an ecosystem.  For example, when a bird species dies out, an ecosystem might lose a seed-disperser.  If honeybees died out, there would be way fewer pollinators and thus way fewer fruits and seeds.  If a type of beetle died out, we might lose a soil recycler. 

Nandina is guilty of taking up a tiny bit habitat that would otherwise be used by native species, though it doesn't appear extremely aggressive.  It has another problem, though.  Nandina berries contain a toxin called cyanide.  Birds in the US haven't figured out how to deal with the poison, and some cedar waxwing birds have died from eating lots of the berries.  The berries can be toxic to any other animal too, so don't eat them. (It probably takes a lot of berries to hurt a large animal such as a human...still...don't eat them.)

Back to the original question: what's a good naturalist to do?  That depends on who you ask.  Some will say to never plant nandinas.  Others say plant them but clip off the berries this time of year when birds start foraging.  Others say don't worry about it - eventually the other species will adapt and nandina will become another important part of our ecosystem.  The only problem with this last option is that adaptation takes hundreds to thousands of years, so we won't find out how nandinas mesh with our Middle Tenneessee ecosystem for a looooonnnngggg time!  What do you think we should do?

In Praise of Black Walnuts

You might want to wear a hard hat next time you go to the outdoor classroom.  There is a black walnut tree in the back corner, and it's walnut season!  If you sit there long enough, you might just witness the loud thud of a walnut hitting the ground.

Here's our black walnut tree.

Black walnuts (Juglans nigra, meaning black Jupiter nut) are beautiful trees.  I like them because they provide light shade (not too dark - their leaves are sparse and let the light through), give us delicious nuts, provide food for squirrels and are an excellent source of wood.  The dark walnut wood is so beautiful, strong and light that a full-grown walnut tree can be worth $5000 or more if it is cut down and sold for wood.  Plant a few walnut trees today and harvest them in 30 years for an excellent return on your investment.  Plus you can eat the walnuts in the mean time!  Just be sure to re-plant what you harvest.

Whole in-shell walnuts are available  in grocery stores this time of year.  They are a great snack, and since they take a while to crack open, you can't spoil your dinner with them.  The grocery store walnuts are English walnuts and ours a black walnuts, but our walnuts are still very good to eat.  In fact, their strong wal-nutty flavor makes them superior for adding to ice cream, fudge and cakes.  You just have to catch them before the animals do.

A black walnut with the husk still on.

Walnuts grow with a husk on them that makes them look like big round limes.  The husk contains a chemical called juglone that makes it smell rather pungent and stain your hands brown if you touch it too much (it won't hurt you, but you can't wash it off).  The juglone in the walnut husks also seeps into the ground under walnut trees and prevents some plants from growing, which helps prevent walnut trees from having too many competitors for sunlight and soil nutrients.  This plant warfare technique is called allelopathy, and it's fairly common among plants to have secret chemical wars going on in the soil.  Smell a walnut husk and notice the bitter juglone smell.  You can also smell the same odor in crushed walnut leaves.  Every fall, the walnut leaves fall and add a new dose of juglone to the soil.  Juglone is also a potent dye and is used by dye-makers to color fabric.  You could try this out by soaking a cloth in crushed walnut husks and water.

Black walnut with squirrel teeth marks in the husk - I bet that tasted awful!

My dad taught me a special technique for removing walnut husks: put a bunch of walnuts in your driveway and drive back and forth on them.  You should be left with a bunch of crumbled husks and intact walnuts.  You could also just wait for the husk to turn black and rot away, but by that time your walnut has probably become infested with worms or fungi.

Chewed hole in a walnut shell with the entire nut removed by a squirrel.

After you remove a walnut husk, the next challenge is to open the walnut shell.  Black walnuts have stronger shells than English walnuts.  My dad's trick for walnut shells is to wrap several walnuts in an old towel and bash them with a hammer.  Very fun.  Then you can use tweezers and a nut pick to pick out the walnut pieces from the shells.  It's a messy business, but totally worth it.

Whole walnut with husk, walnut with husk partially chewed, walnut without husk, and opened walnut.

Search around the bottom of our walnut tree and look for walnuts with the husk on, with a rotted husk, with the husk gone and with the shell open.  Look closely and you will find walnuts with teeth marks from the industrious squirrels that like walnuts for the same reasons we do.  Squirrels have gigantic, orange chisel-like teeth that you can see here.  They scrape their teeth through the husk (ick!) and the shell, then dig out the walnut with their teeth, tongue and claws.  If there are enough new green walnuts, you might want to take one with you and open it yourself - they are delicious!

Black walnut tree.  If you click on the picture, you can zoom in a see clusters of walnuts.

Walnut trees do not grow walnuts in order to provide us with snacks.  The walnuts are actually the offspring of the walnut trees.  The nut part is actually a seed.  If you put a whole in-shell walnut in the ground this fall, it will sprout and grow a new walnut tree in the spring.  The food value of the walnut - the part we like to eat - provides food for the new walnut tree until it can grow enough leaves to use the sun for food.

Here's more information on harvesting black walnuts if you'd like to do a more serious walnut harvest.

Growing Black Chickpeas

I met a fascinating plant on the farm this week - the black chickpea.  I'm accustomed to seeing tan chickpeas in the grocery store, but it turns out that chickpea skins come in the same variety of colors as human skins - light tan through yellow to red, dark brown and black.  Maybe it's because I am reading the Hunger Games trilogy (probably shouldn't have admitted that), but these plants sound like something that would be found in the arena - useful and dangerous at the same time.  You'll have to see if you agree with me - check it out:

Chickpea (Cicer arietinum) flower.

Chickpeas (Cicer arietinum) have miniature pea flowers, with the typical pea's asymmetrical petals.  The flowers each contain a tiny, elongate ovary that will elongate into a pod with seeds once the flower is pollinated.  Each pod contains one to three seeds, many fewer than English peas.  Chickpeas, regular peas and beans are all in the same plant family - the fabulous Fabaceae, or legume family.

Green chickpea pods.

The leaves and youngest green pods of chickpeas can be eaten raw.  The enlarged but green pods can be cooked like regular peas.  The mature pods turn brown and contain dry seeds. These seeds are usually eaten cooked.  The black chick peas do not turn black until they are mature and dry, and they retain their black color even after they are cooked.  Regardless of skin color, all chick peas are the same on the inside - tan. 

Chickpea pods and leaves with acid secretion making the plant glisten.

The really strange thing about chickpeas is that their leaves and pods secrete a liquid that contains a dangerous soup of acids (Katniss would know that!).  When you brush against these plants, they feel moist.  If you have any scratches on your skin, you will notice that the secretion burns painfully.  If you go blackberry picking one day then chickpea harvesting the next, you will be uncomfortable!  I imagine if you picked them all day, you might have some skin erosion.  On large farms, chick peas are harvested by machine, so don't worry too much about fingerless chickpea harvesters.  The acid is very useful to the plant.  If you were a disease organism or an insect looking to eat a garbanzo bean plant, you would definitely change your mind when you were burned by the malic, oxalic and hydrochloric acids on the plant.

Besides deterring pests, the garbanzo bean secretion does another important job.  It works just like sweat and keeps the plant cool!  The plants secrete their sweat later in their lifespan when their seeds are mature, and presumably when the growing season is edging toward summer heat.  The sweat keeps their leaves and pods cooler than non-sweating leaves when the temperature is high.  As what happens when we sweat, the plants lose water.  They are at risk of dehydrating if there is not enough soil moisture for them to absorb.  Also, moist things tend to rot or become infected as a general rule, so the acid is necessary to protect the moist plants from rotting.

Nearly dry chickpea pod.

The acid secretion on chickpea plants is both useful and harmful to people.  It tastes good, since acids taste sour.  In fact, one of chickpea's acids is malic acid, which provides the tartness in apples.  The acid secretion can be collected by draping a thin cloth over the leaves, letting it sit all night until dew forms, then wringing out the cloth.  It can be used to make a unique lemonade-type drink.  The harmful part comes from oxalic acid.  Oxalic acid interferes with the absorption of calcium and some other minerals from food, and it can aggravate kidney stones.  Oxalic acid is also found in spinach, and that's why spinach and chickpea leaves should not be eaten every single day, though moderate consumption is harmless.. 

Black Kabuli chickpea.

Above is a black garbanzo bean (chickpea) freshly picked.

So what's the verdict?  Would chickpeas make a great Hunger Games plant?  Edible but covered in burning acid - perfect!

Salty Language

Chicago is beautiful all dressed up in snow, but after a couple of days, the look becomes pretty dingy.  The snow pushed aside by plows reveals its underside, gross from the street dirt.  The snert (snow + dirt) then melts into brown slush pools that look solid but give way when you step on them.  Dogs also decorate the snow as they are wont to do in our neighborhood.  Then there's the salt grime, white or a rainbow of colors, depending on what variety is used.

A salted bike path by the Navy Pier.

It's remarkable how much salt is applied on this city when it snows or ices.  The streets and sidewalks are quickly covered in the stuff.  It does indeed lower the freezing point of water to about 0 degrees Fahrenheit, enabling the snow and ice to melt and run off the sidewalk, so it's a useful substance when it's not extremely cold.  I can't help but wonder what happens to all that salt as it is washed off the sidewalks and down into the drains or soil. 

Salt has bounced off the sidewalk onto the soil above this tree's roots.

Even though life is thought to have originated in the ocean, where there is plenty of salt, life on land has adapted to a low-salt environment.  Land plants are very vulnerable to excess salt because their cells shrivel and break when exposed to salt water.  Try watering a houseplant with very salty water.  It will die.  If the houseplant is a flimsy, soft one, it will wilt and shrivel in a matter of hours.  The tree in the picture above is going to be very stressed in the spring when rain washes the salt down to its roots.  I imagine the city has to replace many trees and use salt-tolerant varieties as much as possible.  It is not uncommon to see screens erected around street-facing gardens to keep the salt out.

The salt that doesn't seep into the soil washes down into the storm drains.  Some storm drains probably go straight to Lake Michigan, but most go to a sewage treatment plant, thank goodness.  Urban storm runoff contains not just rainwater and salt, but everything that drips off the underside of cars, dog waste, pollution particulates that have settled out of the air, and countless cigarette butts.  It contains more toxic compounds than regular flushed sewage. 

Salt isn't usually removed during sewage treatment, and it is released back into the environment with the cleaned sewage water, usually into a river or lake.  The salt then raises the salinity of the river, increasing mortality for aquatic life.

Road salt is the same chemical as what you sprinkle on your eggs in the morning at breakfast: sodium chloride.  It is a necessary compound, and without any salt we would die.  For us here in North America though, too much salt is usually the problem for humans as well as urban soils and river life.  Salt causes problems in our bodies the same way it does for fish downstream from winter stormwater runoff.  It's essentially a water-balance issue.  Have you noticed how thirsty you get after eating a very high-salt food like Fritos or a cheeseburger or almost any meal at a chain restaurant?  That thirst is a symptom of salt imbalance.  The salt has dehydrated our cells just like it does for plants, and our bodies become thirsty, causing us to drink more water to dilute the salt and unshrivel our cells before they break.  The excess salt and water in our bodies causes swelling and a 1-3 pound increase in body weight (also known as water weight), until our kidneys can filter out the whole mess. 

People who eat a high-salt diet long-term maintain that swelling and high kidney workload for years.  It can, depending on one's genetics and other lifestyle factors, contribute to chronic high blood pressure and eventual strokes or cardiovascular problems.  The tiny capillaries in the body can be degraded from constantly having an elevated amount of fluid in them, which disrupts function in the extremities of the body, the brain, the kidneys, the heart, the eyes, and everywhere else capillaries are essential to body function (which is, really, everywhere).  Fortunately, salt is usually only found in such high quantities in processed food and restaurant food, so if you cook for yourself most of the time and just salt your food at the table, you should be OK.

Very large quantities of salt are toxic in the short term, also known as acutely toxic.  Salt toxicity by oral ingestion has been tested on mice (thankfully not on humans).  A dose of 4g of salt per 1 kg of mouse will kill 50% of mice within one day of ingestion (those numbers are called the LD50, or lethal dose for 50%).  If that number is applicable to humans, let's figure out what it means.  A typical 150 pound person weighs about 68 kg.  4g times 68 kg equals 272 g.  So 272 grams of salt gives a person 50/50 odds of survival.  272 grams is about 15 tablespoons.  Ick.  Hypernatremia (salt toxicity) symptoms of thirst, irritiability, weakness and dizzyness kick in way before coma and death, so the problem can be remedied before it gets too bad.  Hypernatremia in humans is actually more commonly caused by removing water instead of adding salt, and we refer to it as dehydration.

Bacteria and other microbes are killed by excess salt the same way our cells are.  The salt causes their cells to shrivel.  Humans have taken advantage of this trait and used salt to prevent microbes from surviving on some foods and spoiling them.  Beef jerky, for example, is "cured" with lots of salt.  You can demonstrate this phenomenon by taking a piece of beef jerky and a piece of raw steak and leaving both out on the counter in your kitchen for a week.  Be sure to check on them daily to notice any smells or discoloration.  Or flies.

Now back to snow.  Seattle has decided it doesn't want to deal with salt pollution problems, and they handle snow clearing in a different way.  Seattle plows the snow with a rubber-coated plow, leaving some snow in a hard-pack on the streets.  Then they sprinkle sand on top of that.  The surface becomes less slippery, and the sand helps cars grip.  The streets are passable for front-wheel drive vehicles and all-wheel-drive vehicles, but they are tricky for rear-wheel-drive cars, such as the police use (oops).  Even though this solution has a slight logistical cost for getting around in winter, it really cuts down on the costs of environmental damage to Puget Sound.  Salt run-off harms fishing and tourism industries in the sound by reducing aquatic life, and it also slows natural nutrient cycling by killing bacteria, so the sound doesn't stay clean.  Seattle-ites would rather have a clean Puget Sound and drive a little slower in the winter.