Episode 20 – Shownotes & Transcript

Welcome to The STEM Sessions Podcast.  I am your host, Jarl Cody.

Every December, I waffle between getting a fresh cut Christmas tree or buying an artificial one

Pre-lighted artificial trees are intriguing

  • You just assemble them and you’re done
  • But we seem to change our decorating style and theme every year – sometime large mono chromatic lights, sometimes small multi-colored fairy lights, sometimes none, so the prelighted trees may not offer the flexibility
  • Plus, artificial trees in general need to be stored, and I refuse to fill up my garage with that much stuff, especially stuff I only use one month of the year

On the other hand, I love the smell and feel a fresh cut tree adds to the house

  • My cats like it, too, and tend to get a wild streak in them with a fresh cut tree
  • But fresh cut trees dry out and get messy as December rolls on
  • Plus, a small part of me is a bit sad it was cut down in the first place
  • Availability of fresh cut trees is usually a function of which weekend I visit the tree lot
  • Because I’m lazy and refuse to get on the Christmas train until well after Thanksgiving, that usually means selection is limited

Past years, I’ve picked out Douglas firs in the six feet height

  • This year, I got a four feet tall Noble fir, and I love the size
  • So much so, I’ve decided future winter solstice holiday seasons will not feature a fresh cut tree, but a live one instead
  • It will be potted and maintained in a quasi-bonsai style, and brought inside and decorated during December

But what type of tree is the question

  • Tree lots sell Noble firs, Douglas firs, Fraser firs, Nordmann firs, Grand firs, spruce trees to name a handful
  • And this got me thinking, what is the difference between a fir and a spruce, and where do pines fit in?
  • Despite exploring North American forests all of my life, my evergreen identifications skills are non-existant

A deep dive into conifers was required, and here is what I learned.

This is The STEM Sessions Podcast Episode 20 – The Cone Bearers

At some point in my education, I learned there are two types of trees – deciduous and evergreen

  • Deciduous trees lose their leaves in the winter and enter a state of dormancy, revitalizing with warmer temperatures in the spring
  • Evergreens do not lose their leaves nor do they experience dormancy in the winter – they are green throughout the year
  • I also learned evergreens and coniferous trees are interchangeable names for the same plants

Unsurprisingly, that explanation is a gross oversimplification

  • First, deciduous trees losing leaves in winter is only a characteristic of trees in colder climates
  • In warmer arid climates, deciduous trees lose leaves and go dormant in the dry warmer season
  • Second, evergreens lose leaves, too – they just do so throughout the year and never all at once
  • Third, the terms evergreen and deciduous are not unique to woody plants like trees and shrubs – they can be applied to most of the plant kingdom
  • Fourth, evergreen and coniferous are not completely interchangeable
  • To be evergreen you don’t have to be coniferous – there are evergreen oaks for example – and not all conifers are evergreen

Even that is an over simplification, albeit not as gross of one

  • Terms deciduous and evergreen are rabbit holes unto their own, and we’ll have to revisit at a later date
  • After all, this episode was inspired by Christmas trees, which are inherently conifers, so we’re going to focus on that term

Conifer is a compound of two latin words: conus (cone) and ferre (to bear)

  • Meaning “the one that bears (a) cone(s)”.
  • So in simple terms, conifers are woody plants – mostly trees, but a few shrubs – whose seeds are contained in cones
  • Confiers are gymnosperms meaning their seeds are not contained within a fruit like those of angiosperms or flower plants.
  • Therefore, the primary purpose of the cone is to protect the seeds

Taxonomically speaking, conifers are found in the division Pinophyta

  • When I read “division” I was confused – there is no division in the taxonomy I learned in high school
  • I learned Kingdom, Phylum, Class, Order, Family, Genus, Species using the mnemonic sentence “King Philip Came Over From Germany Swiftly
  • Is division a buried sub-category that just doesn’t get talked about?
  • It turns out Phylum only applies to the animal kingdom, and is replaced by Division in the Plant and Fungus kingdoms

So conifers make up the division Pinophyta

  • And within the division, all conifers the class Pinopsida
  • Within the class Pinopsida, there are four orders: Pinales, Cordaitales, Vojnovskyales, and Voltziales – the latter three are fully extinct
  • Meaning all conifers living today are found in the order Pinales
  • Incidentally, the fossil record of conifers dates to 300 million years ago

Living conifers are further divided into seven families

  • Some I’ll mention only briefly
  • Others, namely the ones I have firsthand experience, with more detail
  • And for the most part, I will not be using the actual scientific names, because I can’t pronounce them, but they’re in the shownotes if you’d like to read them

Araucariaceae – Araucaria family

  • Three genera and 41 extant species
  • One of the older families of conifers
  • Today found in the southern hemisphere but wide spread during the dinosaur age – petrified wood in Petrified Forest National Park in Arizona is of the Araucaria family.

Taxaceae – Yew family

  • Three genera, approximately ten species
  • Mostly found in northern hemisphere
  • Generally toxic to humans, but medicinal compounds can be distilled

Cephalotaxaceae – Plum-yew family

  • Three genera, approx 20 species
  • Closely related to Taxaceae
  • Exclusive to east Asia, with the exception of two species in southwestern and southeastern US

Sciadopityaceae – Umbrella-pine family

  • One genus, one species – the koyamaki or Japanese Umbrella-pine
  • Exclusive to Japan

Podocarpaceae – Yellow-wood (or Podocarpus) family

  • 18 genera, up to 200 species depending on the classification system
  • Primarily southern hemisphere, with some species ranging north of the equator
  • Many species grown across the world as garden trees – can be trained as hedges, privacy screens

Cupressaceae – Cypress family

  • 30 genera, 140 species
  • Found both hemispheres, world wide
  • Cypresses, junipers, redwoods including the coastal redwood and giant sequoia
  • Largest geographical range of the conifer family

Pinaceae – Pine family

  • When I think of conifers, this is the family that I picture
  • 11 genera, 250 species
  • Found in the northern hemisphere, with one species jumping the equator
  • Pines, spruces, cedars, firs
  • Largest conifer family in terms of species count, and second largest in terms of geography
  • And when a conifer is decorated as a Christmas tree, the species is most likely from the Pine family

Now that we’ve described the family tree, let’s circle back to the cones for a moment, because they are a defining feature of conifers

  • There are male and female cones, just like there are male and female flowers
  • Male cones produce pollen which is dispersed on the wind with the intent of fertilizing the gametophyte inside female cones
  • Resulting seeds are protected by the female cone
  • Both male and female cones can develop on the same tree

Depending on species, the cones take months to years to reach maturity

  • When ready, some cones open allowing seeds to be carried away by the wind
  • Other cones disintegrate to release the seeds
  • Others have evolved to be opened and dispersed by birds and small mammals
  • Some cones require the heat of fire to open

I’m sure most of us have a picture of a pine cone in our heads – a brown, spikey, scaley, woody object

  • But not all conifer species have woody cones
  • Some cone’s scales are fleshy
  • Some are brightly colored
  • Some are sweet
  • I remember the first year my Podocarpus developed cones – They looked like giant blueberries which completely confused me because I knew podocarpus is a conifer species and therefore must have cones – so what the hell were these berries?
  • But my firsthand experience has been limited to trees from the pine and cypress families with each species I’ve encountered developing cones that look like the typical pine cone
  • Just goes to show experience doesn’t always give one the whole picture

After cones, the next defining feature of conifers is their leaves

  • Typical conifer foliage is not the broad leaves of oaks and maples
  • Instead, conifer leaves are relatively long compared to their width
  • Pine family have needle like leaves ranging from an inch to five or six inches long
  • Podocarpus family are not needle like, but are close to it, still much narrower than they are long – the tree in my yard has needles approx a quarter inch wide but 2-3 inches long
  • Cypress family  are not needles at all; they’re flat narrow thin leaves, and are arranged in a scaled finger pattern

Conifer leaves are part of the order’s adaptation to environments inhospitable to other trees

  • Conifers are generally sclerophyllous, meaning they are hard leaved
  • Lose less moisture than broad leafs and can tolerate dry summers
  • Dark green can absorb more sunlight in winter or weaker sunlight in upper latitdues

Physically speaking, most conifers display monopodial growth

  • This is the classic Christmas tree shape: a single, straight trunk with smaller branches shooting off in all directions from that central trunk
  • This shape is maintained through apical dominance: a characteristic in which the central stem of a plant – the trunk in this case – grows more strongly than the side stems or branches
  • Further, any given branch also exhibits apical dominance within itself meaning the branch emerging from the trunk will grow more strongly than any sub-branches or twigs it produces

Apical bud is the location where growth occurs

  • Bud on the trunk releases hormone that inhibits growth of side buds further down the tree
  • If bud is damaged or removed, the hormone dissipates and growth is now concentrated on the lower branches
  • Removing this apical is common when training trees to grow in a specific shape
  • I have two types of conifers in my yard – a podocarpus and several cypress trees
  • Both are used for privacy, but needed to have different shapes
  • Podocarpus needed to be wide, so once it reached the appropriate height, I trimmed the central shoot, and energy was directed to the lower branches causing them to grow
  • Cypress trees were planted in a row, so we allow them to grow tall, keeping the lower branches short
  • Growth mechanic of apical dominance is most likely an evolutionary adaptation
  • If energy can be concentrated at the apical bud on the trunk rather than on side branches, the tree can grow taller allowing it to capture more sunlight for photosynthesis than its neighbors

Growth of conifer trees is the stuff of records – the tallest, largest, thickest, and oldest trees in the world are all conifers

  • Tallest specimen is a Coast Redwood (Sequoia sempervirens) named Hyperion in California at 115.5 m (379 ft)
  • Largest specimen is a Giant Sequoia (Sequoiadendron giganteum) named General Sherman in California with a volume of 1487 m^3 (52500 ft^3)
  • Thickest is a Montezuma Cypress (Taxodium mucronatum) in Mexico with a diameter of 11.4 m (37.5 ft) – though depending on methods of calculation it varies from 9.4 m to 14.0 m (30.8 ft to 46.1 ft)
  • Giant Sequoia which has a more traditionally circular cross section is just shy of 9 m (29 ft)
  • Oldest is a Great Basin Bristlecone Pine (Pinus longaeva) named Methuselah in California at 4853 years – though recently another was dated at 5062 years but that doesn’t seem to have been confirmed yet

Growth has resulted in them playing an important role in our daily lives

  • Conifers live in a wide range of ecosystems and environments
  • Equator to the higher latitudes, deserts to mountains
  • Adorn many of our homes and parks
  • Much of outdoor recreation takes place in conifer forests
  • Comprise the vast majority of material in our timber industry from basic construction lumber (2x4s, etc) to paper
  • Also represent the world’s largest carbon sink thanks to their geographical range and mass

So let’s finally get to the question that started this investigation: Are names like pines, firs, and spruce just colloquial, or is there actual definition behind them

  • Pines, firs, and spruces are all different genera within the Pine family, but they are incorrectly used interchangeable in every day vernacular
  • When shown a photo of a tree from the pine family, a random person will almost certainly say that’s a pine tree
  • They all have needles, they’re all green, they all have cones, but there is a difference
  • Pine trees have long needles, with multiple needles emerging from the same point – they grow in clusters
  • Firs and spruce needles grow individually along the branch
  • Spruce needles are sharp with a square cross-section
  • Fir needles are softer and flat (they can’t be rolled between your fingers)
  • So, yes, there are technical differences

Thank you for listening to The STEM Sessions Podcast. 

This episode was researched, written, and produced by Jarl Cody.

Here at The STEM Sessions, we strive to share accurate and complete information, but we also encourage you to do your own research on the topic we discussed to confirm the accuracy of what we’ve presented.  Corrections are always welcome.

Shownotes, contact information, and details of our other activities can be found on our website thestemsessions.com

If you received value from this episode, and wish to give some back, please visit thestemsessions.com/valueforvalue for ways to support the podcast.

Finally, please remember STEM is not a tool exclusive to experts, policy makers, and talking heads.  Every presenter is susceptible to unconscious and, sometimes, deliberate bias, so always verify what you read and what you’re told. 

Until the next one, stay curious.

REFERENCES

“Frequently Asked Questions”

“Conifer”

“What is the World’s Tallest Tree?”

“What is the oldest tree in the world?”

“Apical Dominance”

“Pinales”

“Conifer”

“Evergreen”

“Deciduous”

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