How to Read Bark Scars in Sourwood Trees

Sourwood trees are among the first to turn colors in the Fall.

The sourwood trees in our outdoor classroom are the first to put on their fall colors for the season.  Sourwoods are wonderful, smallish trees with beautiful foliage and interesting bark.  They are named for the sour taste of their leaves, which you can experience if you touch a bit of torn leaf to your tongue.  The leaves contain oxalic acid, which tastes pleasantly sour (all acids taste sour).  Tasting the leaf is not harmful, but the leaves are not considered edible and shouldn't be eaten.

The small orange-leaved tree in the picture is one of our sourwoods.

We have two sourwood trees.  Above you can see the location of one sourwood - it's the orange-leaved small tree in the center of the picture.  See if you can find the second sourwood tree when you visit the classroom.

Lenticels in young bark of the sourwood tree.

Sourwood bark is wonderful - it has so many visible features that give clues to what the tree is doing and what it has gone through during the tree's life.  A lot of people think tree bark is a dead part of the tree, but the opposite is true: tree bark is a living, important tree tissue that changes as trees grow.  Bark is mostly responsible for moving sugars (a tree's food, made from photosynthesis) between the leaves and roots.  Bark is filled with phloem tubes for transporting the sugar.  The above picture of a young twig contains tiny spots called lenticels.  Lenticels are tiny holes in the bark to allow air to get into and out of the inner tissues of the twig.  Compare the above twig to the one below.

Sourwood twig with cicada damage.

The twig in the picture above is about the same age as the one in the previous picture, but something looks wrong!  This giant gash in the bark is the healed wound cut into the bark by one of last year's cicadas.  Cicadas cut into young bark and lay their eggs in the gash where the developing offspring can feed on tree sap.  The living bark responds by slowly growing a scar to heal the wound and seal off the wood, which is what you see above.  

Older twig with young bark splitting as the twig grows larger.

Bark naturally stretches and tears and re-heals to allow tree twigs and trunks to increase in girth.  The twig above shows the first tears in young bark as the twig is getting thicker through the years.  The stretch marks get bigger as the tree gets bigger, and large branches and trunks might have deep furrows in the bark.

Scar from where a branch broke off the tree.

When branches fall off or are broken off, the bark around the broken area swells up and heals over the scar.  The scar above looks like a pretty big scar, so I suspect the branch that used to grow here was torn off unevenly.  Notice the larger tears in the normal bark above and below the branch scar.

Large gash in bark that is healing over - possibly damage from planting the tree.

Here is an even bigger scar from some major damage to the trunk.  Something cut into the bark of this tree.  Perhaps it was damaged as it was being transported or planted here.  Such an injury can weaken or kill a tree, because it can let diseases into the tree, just like a wound in our skin can become infected.  I wish more people realized this so they wouldn't carve their initials into trees' bark.  Nevertheless, this tree appears to be healing from its damage.  You can see exposed wood through the gash in this bark.  If the wound to this tree were to have cut through the bark all the way around the tree, the tree would have died, since the bark would be unable to move sugars up and down the tree.  Plant managers who need to kill trees use this technique - it's called girdling a tree.

Check out the bark on our sourwood trees and look for lenticels, branch scars, normal tears in the bark, and possible injuries to the bark.  Then take a look at other types of trees and see if you can read the scars in the bark.  Can you tell where branches used to be?  Can you see how the bark split at the tree got bigger?

Click to zoom in and see how the leaf veins connect.

When you check out the bark on our sourwoods, be sure to look at the leaves too.  Sourwood leaf veins are large, and it's easy to see the network of how the veins connect.  Also be sure to look for the remnants of flowers, now turning into fruits, at the ends of some of the branches. 

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.

How to Grill a Pie

When I took the pictures for this post, I didn't know if the title would be How to Grill a Pie or How Not to Grill a Pie.  As you can tell, there's a happy ending to today's blog post!

There has been a giant bag of rhubarb burning a hole in my freezer for about a month now.  I've been dying for an excuse to make a rhubarb pie, the most delicious dessert on the planet.  With temperatures over 105 for the last several weeks and the air conditioner laboring to keep the house under 80, I haven't turned on the oven, dishwasher or dryer since the heat wave started.  And yet, there was the rhubarb.  And it was our turn to host dinner club.  And nothing is better than rhubarb pie.  Maybe the flavor of rhubarb would compensate for our guests having to blot sweat from their faces all during dinner.

Heat-dispersing platform for baking a pie in the grill.

I called Mom to remind me about the perfect ratio of sugar to rhubarb, and she suggested opening a window to vent the kitchen if I must make the pie.  Then I got to thinking about our grill.  It's really just an outdoor gas oven, right?  If I could figure out how to cook the pie out there, the house would still be cool for dinner.  So this time I called Dad, and he thought it would work, but I should put a heat-deflector under the pie dish with some air between the heat-deflector and the pie to allow air and heat to circulate.  The above picture shows my system for evening out the heat from the burners, with the metal grill for elevating the pie off the cast iron pan.  I think any baking sheet would work in place of the cast iron pan for a heat-deflector. 

Pie with edge protector for protecting the crust edge from burning.

To the left of the pan, you see a crucial element for the success of grilling a pie: an oven thermometer.   I preheated the grill to 400 degrees, the temperature required by my pie recipe.  My grill doesn't have any sort of temperature gauge besides purely decorative 'low' and 'high' markings, but after some playing, I discovered that keeping both burners on low would keep the temperature somewhere between 375 and 450 - close enough! 

Success!  One rhubarb pie baked in the grill.

The pie was supposed to bake for 50 minutes.  I checked it every 15 minutes or so, and ended up letting it cook for about an hour and 15 minutes.  It cooked perfectly - no burnt crust and no grill taste - just delicious, tart, heavenly rhubarb.

Some tips:

• Clean the grill really well before you start, especially if your grill is full of meat fat that might burn and smoke your pie with carcinogenic meat fat smoke.
• Use metal pans so they don't crack from uneven heat.
• Elevate your pie dish off of the pan underneath it - this is a must.  I also cooked cornbread in the grill, and I made the first batch straight on the pan and burned the bottom.
• Put foil under the pie to catch any juice dripping out of it - you don't want smoke from burning sugar to flavor your pie.
• Check frequently until you trust your temperature, but just barely crack open the grill to keep the heat inside.
• Maybe try some cornbread or something easy first to learn the process before you use expensive and time-consuming ingredients.

How to Read a Twig

Everyone knows that you can chop down a tree, count the rings in the wood and tell how old the tree is.  Trees grow in spurts, usually one growth spurt per spring/summer, and they add a new layer of tree where the bark meets the wood.  They add a new, microscopic layer of bark, and a layer of wood thick enough to count when the tree is cut down.  More on bark and wood at this previous post.

I bet you didn't know that you can figure out how old twigs are too, and you don't even have to cut them down to tell.  Twigs have so much to say once you know how to read them.  This post is best if you have a twig and a magnifying lens nearby, but in case you don't, I've included some fabulous drawings to help you.  I hired a professional artist and spared no expense.  Twig details are usually too small to photograph well, unless you have a buckeye twig which are out-sized and easy to see.  I haven't found a buckeye in Chicago yet, so you'll have to make do with these drawings instead of photographs.  All the parts I'll discuss here are visible on all twigs, but most are a little smaller.

Artist's rendering of a buckeye twig on archival-quality notebook paper.

 First, find the buds.  Buds are live twig-tips covered in scales and protected to survive the winter.  The end buds, called terminal buds, are at the ends of twigs, and they are usually the largest.  If you cut open a terminal bud under a microscope, you would see layers of yet-to-be expanded leaves and stem material.  In the spring, terminal buds grow long and send out leaves, extending the twig.  There are also axillary buds, which grow just above every leaf a tree has (unless the tree is a sycamore, then axillary buds grow inside the leaf stem base).  Axillary buds can expand into twigs and leaves too, but they are usually much smaller and less mature.  They often only grow in spectacular growing seasons or if the terminal bud is cut off.

Buds - terminal and axillary

 In the winter, you can see scars on the twigs where previously-grown leaves have fallen off.  Axillary buds are above the leaf scars.  Buds are covered by bud scales, tough leaf-shaped brown things protecting the bud in winter.  Bud scales fall off in the spring when the bud starts to grow, and they leave scars that encircle the twig in tiny, bunched lines.  If you look back from the tip of a twig, you can find scars from last winter's bud scales.

Bud scales, bud scale scars and leaf scars.

 Since bud scales are produced each winter and fall off each spring, they leave annual scars on the twig.  You can tell a twig's age by counting back from the tip of the twig and seeing how many sets of bud scale scars are present on the twig.

Twigs also have tiny dots on them called lenticels.  If you zoomed in on a lenticel, you would see an opening with a tiny mouth-like structure that can actually open and close.  The opening is called a stoma, and it is for allowing exchange of oxygen and carbon dioxide into the air - basically it allows the plant to breathe.  You have probably heard of stomata (plural of stoma) on leaves before, and these are the same thing, just on bark instead.

Lenticels and age of twig

 The age of the whole twig can usually be determined by counting back from the longest branch.  You can tell the age of side branches too, by counting the bud scale scars back from their tips.  You can also tell how good the growing season was by the distance between bud scale scars.  A good growing season will have a long distance between bud scale scars.  A dry or cool year will have less growth.

Deer like to eat terminal buds off of edible trees because of the tender, living material inside.  When that happens, axillary buds are activated, and often several side-branches will grow during the next summer.  This can give a branch a bushy appearance.  When you trim a branch by chopping off the end of it, the same thing happens.  Whatever grows back will be bushier.  If you trim off an entire side branch where it joins a larger branch, the next year's growth will not be bushier - instead the terminal bud elongates and the branch just gets longer.  You can influence the shape your trees and bushes by trimming off side branches completely to encourage them to grow in the direction of the remaining terminal buds.

Twig life history

Six Interesting Things About Garlic

I spent the better part of a day harvesting garlic yesterday.  It is a pleasing job made even better by the garlic aroma that ebbs and flows around your head while you work.  At one point, the farm owner was harvesting basil upwind, and I had a wonderful aromatic pesto experience.  I have always wanted to grow garlic in my home garden, and I learned enough yesterday to try it this year.

To grow garlic, you plant a clove in the late summer and let it grow.  It grows a stalk with leaves above ground and begins to build a large bulb underground.  When the above-ground leaves start to die off, you know the bulb is ready to be harvested.  To harvest, stick a pitchfork into the ground a few inches away from the bulb and pull up the bulb and soil.  Gently brush off much of the soil and pull a leaf or two off if they are mushy and dead.  The fresh garlic is fabulous - mild and slightly green tasting, but you can cure it and keep it to use throughout the year.  To cure the garlic, let the whole stalk and bulb dry outdoors for two weeks or so.  Then you can cut off the top of the stalk and roots and store the whole thing in a cool, dry location.

Here is a row of garlic and one fifth of my garlic harvest ready to go to the drying racks:

Garlic is an amazing and powerful plant.  In no particular order, here are some interesting things about garlic:

1. Eating two cloves of garlic a day reduces your risk of cancer.  (reference)  If you crush the cloves, let them sit for 15 minutes, then cook with them, they will cause your body to produce more of its own antioxidant, hydrogen sulfide.  Antioxidants reduce the risk of cancer. 

2. Garlic also helps maintain elasticity of the blood vessels, reducing the risk of cardiovascular disease.  It also has many other health benefits that are less rigorously demonstrated.  Garlic is anti-viral, anti-parasitic, antibacterial and anti-fungal. 

3. Garlic makes any savory dish taste better.  It helps bring out the other flavors in food even as it adds its own richness.  It is good lightly sauteed (don't burn it), roasted whole, cooked in broth, or even crushed raw into hummus or pesto or salad dressing.  To avoid burning garlic when sauteeing, add it as you finish sauteeing the onions and 1-2 minutes before you add the major ingredients to the pan.

4. Garlic scapes are delicious and only available for a flash in the spring.  Garlic scapes are the flower stalks of the garlic plant.  They have a gentle garlic flavor.  They can be stir-fried or sauteed.  Another farm worker brought in pesto made from only garlic scapes, olive oil and pine nuts, and it was fantastic.

5. Garlic is in the onion family, which includes all types of onions, chives, leeks, ramps and shallots.  These plants grow all over the world and are used in almost all cultures' cuisines and medicines.

6. Garlic plants are mostly all clones of each other.  Garlic seeds are not usually planted, and seeds would be the offspring of two garlic plants.  Cloves are parts of one plant, so when they are separated off and planted, they are genetically identical to the plant they came from - clones.  Garlic is very easy to grow from cloves, and the results are predictable.  Seeds take much longer to grow, and each seed results in a plant that may be bigger, smaller, less pungent or otherwise different than the parent plants. 

I'll leave you with my foot - toes looking fabulous from a recent trip to New York and lots of mud from harvesting after a good rain.