Mike Turner

Should have been more specific.   I'm asking about dicot trees, not monocots or plant growth types that have no temperate zone equivalent (palms, papayas, etc.).

When growing trees native to temperate zones, practically every angiosperm or gymnosperm species that has multiple cultivars has at least one columnar cultivar.  But columnar cultivars of trees native to tropical zones seem to be practically nonexistent, at least I can't find any.  Even among popularly grown species with multiple cultivars such as avocado, cultivars described as "columnar" are still fairly broad, just not as broad as the non-"columnar" cultivars.  There are none as narrow as a lombardy poplar or columnar apple or plum tree.  Why is this?

It doesn't have that bitter flavor normally associated with the green skin .  Perhaps the purple pigment in the flesh absorbs enough light to keep the green reaction from occurring.

Daron Williams wrote:

Mike Turner wrote:Potatoes are a perennial vegetable here, producing 2 crops a year.  They grow from March through June, then going dormant until September, then growing until first frost in November.  Any tubers I miss or leave in the ground go on to grow in the next appropriate growing season.

That's great--I actually have volunteers coming back up in my area to. I debated making the case for them to be considered a perennial root vegetable and just decided to leave them out. But you make a good point about growing them in warmer areas. Do you move yours around? Just wondering if you ever have pest issues with them growing in the same spot for a longer time period. I hear conflicting views on that being an issue. Thanks for sharing!

No pest or late blight problems. My chickens take care of the potato beetles and my climate is too hot and dry for leaf blights.  I'll move them every couple of years.  The main problem with perennializing them is they tend to set the tubers higher in the soil with each season, so I have to mound them up a bit to keep all of the tubers underground.  Also you have to identify the bad tasting "glassy" potatoes that sprouted and gave their all to produce the new crop, but they are usually easy to distinguish by their aged skins.  Also potatoes left in the ground a few months before harvesting may have a few wireworm tunnels through them.  Purple potatoes don't have the green skin when exposed to light problem that you have with red or brown skinned potatoes.

Potatoes are a perennial vegetable here, producing 2 crops a year.  They grow from March through June, then going dormant until September, then growing until first frost in November.  Any tubers I miss or leave in the ground go on to grow in the next appropriate growing season.

If you look at the earth's history since the Cambrian, compared to prehistoric norms, our current time has unusually low temperatures and CO2 levels.  The only time that came close was the latter half of the Carboniferous through the first part of the Permian era.  Through most of their evolution, plants were living in a world with ice-free polar regions and a CO2 level 3 to 4 times higher than the current levels and those are the  CO2 levels that .they are best adapted for.  The fall line along the east coast of North America is where the sea shore was located for the majority of the time since the Atlantic ocean was formed and it left its mark on the topography.  

There was an entire plant community, the polar deciduous forest, that existed above the arctic circle in North America until the poles started freezing up about 8 million years ago.  This plant community was populated with the tree species that are now found in the temperature zone.

With C3 and C4 photosynthesis, plants absorb CO2 and release O2 when they are exposed to light.  There is the side reaction of photorespiration in C3 plants where plants absorb O2 and release CO2 that occurs when CO2 levels are low.  

The only plants that absorb CO2 and release O2  at night are plants with crassulacian acid metabolism (CAM), C3 and C4 plants do this during the day.  

The terms "light reaction" and "dark reaction" in photosynthesis can sometimes be confusing , thinking that light reactions occur during the day and dark reactions occur at night. Light reactions can occur whenever the plant is in light.  Dark reactions don't require light to occur, all they require are the chemical products produced by the light reactions and, for most plants, occur alongside the light reactions when the plant is exposed to light.

O2 levels were below present day levels during the Cambrian era.  The first O2 peak didn't occur until the Carboniferous era and a second lower peak occurred toward the end of the Cretacious.  

Neither insects or land animals existed during the Cambrian era, insects first appeared during the Ordovician era, and the first land animals appeared during the Silurian era.

There has been no correlation between CO2 and O2 levels through the ages as there are factors in addition to plant and animal activity that effect their levels.  CO2 is added by volcanic activity, especially the super eruptions that formed the Deccan and Siberian traps.  CO2 is removed by newly exposed rock when new mountain ranges are formed.  O2 is also removed by oxidation of newly exposed rock during mountain building sessions.

Not all of the carbon put into the soil by plants is respired by soil organisms, especially when deposited into anaerobic conditions.  Coal and oil deposits are the result of this.

If you look at a graph of world CO2 levels and temperature from the Cambrian era to the present, you see little to no correlation between the two.  But there a strong trend downwards in CO2 levels starting from 7000ppm in the Cambrian and dropping down to 180ppm during the Quaternary glaciation, the most recent downward excursion being 20,000 years ago.  This drop in CO2 levels is to be expected since plants are busy pulling CO2 out of the air with the resultant fixed carbon being deposited into the ground and on the sea floor.  A portion of this sea floor carbon gets subducted deep into the earth's interior via plate tectonics, becoming forever lost to the biosphere except for what little bits of it get released via volcanoes and mid-ocean hydrothermal vents.   So the general long term trend is for atmospheric CO2 levels to drop as carbon gets pulled out of the air and put into the ground.  

Angiosperms first appeared during the Cretaceous when CO2 levels were in the 1700 to 1800ppm range and have had to adapt  to steadily dropping CO2 levels from that time forward. C3 photosynthesis is the original chemical pathway that evolved in algae during the Precambrian era  and is found in all sea plants and most land plants. But 7 million years ago some groups of monocots and dicots evolved C4 photosynthesis in response to the extremely low CO2 levels they were experiencing during the Quaternary period.  A drawback of C4 is that it works best at hot tropical temperatures, limiting its use in the cooler parts of the globe, so 85% of the world's plants are still C3.

If you look at a curve of plant growth rate vs. CO2 levels, it rises sharply with increasing CO2 levels until CO2 levels reach 1200ppm where the growth rate starts to level off.  This increased growth rate at higher than current atmospheric CO2 levels has long been known to commercial greenhouse growers, many of whom use CO2 generators to maintain a CO2 level in the greenhouse of between 1000 and 1500ppm.  At these higher CO2 levels, plants grow faster, have higher yields, produce larger, thicker leaves, larger flowers, require less water, and are more resistant to environmental stresses.   Leaves grown at these higher CO2 levels produce fewer stomata and have to open them less to obtain the required CO2, increasing their drought tolerance.

Photorespiration, an inefficiency in the photosynthetic process where the enzyme RuBisCO reacts with 02 rather than the desired CO2, disappears at 1200ppm, but gets worse and worse as CO2 levels drop below that point, and is apparently as artifact of low CO2 levels.  C4 photosynthesis minimizes losses due to photorespiration.

At the other end of the scale, growth and seed production in C3 plants drops off rapidly at lower than current CO2 levels.  An Arabidopsis growing at 180ppm, the lowest CO2 levels experienced during the last ice age, had only 8% of the growth rate of the same plant growing at current CO2 levels.  Below 150ppm, C3 plants essentially stop growing, so the 180ppm lows during the Quaternary glaciation came within spitting distance of killing off many C3 plants.  

CO2 levels were 180ppm st the peak of the ice age, slowly rose to 270ppm as we came out of the ice age, then continued rising as human activity added CO2 to the atmosphere and is over 400ppm now.  This boost in CO2 levels has goosed plant growth rates and is part of the oomph behind the increase in crop yields helping to feed the growing human populations.  Satellite images are showing an 11% increase in foliage cover in arid regions around the world from 1982 to 2010.  The spread in the  seasonal cycle in CO2 levels monitored at Moana Kea observatory increased from 14ppm in 1975 to 17ppm in 2013 as worldwide plant photosynthetic activity is ramping up with rising CO2 levels.

So it looks like plants are best adapted to growing in the mid-1000's ppm CO2 atmosphere they originally evolved in, are showing reduced growth rates/seed production and displaying metabolic derangements like photorespiration in our modern CO2 impoverished atmosphere.  So while some humans might be concerned about rising CO2 levels, the plants are saying "bring it on, we're half starved out here".

Flower pollinating birds found outside of the tropics is unique to the New World.  Sunbirds, the hummingbird's counterpart in Africa and Asia, are native to tropical regions and don't migrate into the temperate zones during the summer, unlike hummingbirds that range north to Alaska and south to Tierra del Fuego during their respective summers.

Sunbirds have bright, jewel-like colors, but aren't as good at hovering as hummingbirds, so flowers that are primarily pollinated by them often include a built-in perch into their flower structure. A good example is the bird of paradise flower (Strelitzia) where the "beak" of the flower provides a perch for the sunbird to perch while it probes for nectar in the orange flowers that form the "bird's crest".

Despite being a native of Asia and not having evolved with the hummingbird, the mimosa tree is one of the best hummingbird food sources that can be grown in upstate SC, providing two and a half months of continuous bloom from June to August during which time the tree is alive with hummingbirds,  butterflies,  bees, and pollinating flies.

My ducks have been very effective at controlling deerflies and horseflies on my property.  Not by eating the adults, but rather by their feeding activities along the margins of my 2 acre pond and in various boggy areas where their feeding activities target deerfly and horsefly larvae that live in mud and shallow water.  When I first moved here, during deerfly season (May) I would typically have 2 to 3 flies buzzing around my head whenever I was outside.  Within 2 years after getting 14 ducks, deerfly populations have dropped to where I see less than 5 of them during the entire season.  Horsefly populations in late summer have also dropped to where I only see 1 or 2 during their season.

The duck's feeding activities have changed the profile of the pond's shoreline.  Where there used to be a constant slope entering the water where it becomes a mud floor sloping away into deeper water, there is now a mini 1 foot high cliff with the several inches of water at its base.  The duck's mud filtering dabbling feeding activity has removed the loose mud in the shallows and into the bank along with any fly larvae living in it.