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The growth pattern of conifers in general follow the same pattern of growth
as found in broadleafed though there is the tendency to the conical form.
What effects the growth pattern more than anything though is the proximity
of other trees and available light. Assuming that wind is not a factor (as
with isolated bristlecones), one can expect the tree to spend most of its
energy as a juvenile growing toward the light source as quickly as
possible. This means that in a dense wood the tree would sacrifice branch
growth in favor of trunk growth until it reaches an acceptable light source
when it would then begin to branch more laterally. To say that any one of
these trees has a "pure form" would be incorrect as the tree will take
advantage of its situation either as a single, isolated plant or as part of
a dense wood.
Today we can see ornamental, non-hybridized conifers planted in isolation
and given proper care will have a tendency to the conical (Christmas tree)
form but this situation is uncharacteristic of their growth in the wild.
The simple reason why lower branches are not present in most wild
specimens is simply because there is not enough light at lower levels to
warrant spending the energy to grow branches beneath the canopy level.
Same is true in a rain forest. Trees which are singular (not in a stand)
will not grow as tall as trees in a stand because there is no need to
expend the energy to out-compete the smaller undergrowth or the rest of the
woods in general. Fourth level forests (the most mature stage of forest
growth) comprise trees of all kinds that sacrifice lateral for vertical
The "ancient" trees we have left today are few, but telling. The umbrella
pine, dawn redwood, and larch are all strongly conical when left in
isolation from competition and truly they have very rigid forms but they
are not known to have ever developed in the wild this way. The gingko is
special because we know from Japanese records that the trees were selected
over the eons for broader shape so that they would produce more thick
branches and provide more wood for building houses (because gingkos are
very fire-resistant), however there is a strongly pyramidal variety that is
less common then the broad-branched variety which is most popular for
ornamental purposes. What each of these plants has most in common is the
ability to throw sports of leaves along the trunk. In the days of the
dinosaurs these trees were most likely only going to survive by growing as
tall as possible and producing as few branches and leaves as possible until
they reached above the reach of dinos looking for a tasty meal.
The umbrella pine grows excruciatingly slowly (6" in a good year) while the
dawn redwood can grow exceedingly fast (6' in a good year). If speed is a
factor in survival then why the big difference? The theory is simply that
umbrella pines were not favored food and in any event are not known to grow
very tall (80') today though they are exceedingly dense in needles. They,
like the laughable monkey puzzle, probably used their needles as a defense
to make them less palatable. Dawn redwoods had to use speed because the
soft fronds are very palatable to animals even today so the effort to
redirect energy into growing above edible level was an immediate need.
What the dawn redwood does do, besides growing so fast, is to grow its
lower branches higher than edible level as a form of defense. Lower
branches of dawn redwoods grow "up" along the underside of the tree and
once they have reached beyond the width of the tree leaf profusely. Leaves
in the inner part die though there are always (this is important) sports
along the trunk defended by dense branches with no leaves on them until the
end of the tree. That's why dawn redwoods look like other conifers in that
there are no leaves on the interior. But in the dawn redwood you get the
sports on the trunk. So what's going on is the tree has prepared a "last
defense". In case all the outer leaf bracts are eaten the tree still has
leaves which are unreachable to all but the most determined predator. Left
alone and totally de-leafed the tree still has a chance to gain
photosynthesis from the sports along the trunk while it concentrates on
re-leafing itself and growing taller. This kind of event is naturally
disasterous to the tree but it works. Larches work the same way.
Gingkos are no different but you have to see them in the lesser-known
conical form. An interesting note is that today nothing eats gingko
leaves. Also the tree knows no pests or disease of any kind (ask my deer,
they eat everything else!).
You might guess what the "safe height" was in the case of all these ancient
trees but particularly in the two oldest: the gingko (Cenozoic) and dawn
redwood. If there were forests comprised of either trees you might guess
how high sauropods could reach based on what natural height these trees
would reach before branching out into a canopy in a forest environment.
Unfortunately neither of these trees has ever been seen in such a state.
Gingkos can no longer propagate naturally without direct human
intervention. Insects nor birds seem to do the trick. Gingkos have not
been planted in forest-like situations and it would probably take two or
three hundred years to find out if they were planted in such a way now.
Dawn redwoods were found only so recently (1945) and then only from a small
stand of trees which averaged about 60' and they were not densely packed
together in a forest setting. The stand was isolated and on a mountain
which could further explain the apparent slow-growth of the trees and the
dwarfed stature of them. Soil was also poor and dry. This combination of
factors may have caused their reason for survival, stunting growth and
retarding aging. Today's oldest dawn redwoods grown from that stand are
cultivated as specimens isolated from each other and thus we aren't able to
judge how they would act in the wild (largest one I know of is now 160').
We would need a trial stand grown as a laboratory forest in order to
determine how they would act in the wild left to their own devices. That
might not be too much help either given that we do not know what kind of
element they would have prospered in except that we do know they favor wet,
loamy soils with a fairly shallow water table (6'-12'). Would there have
been other plants growing nearby that formed a symbiotic relationship
necessary for mutual survival? Certain organisms, insects, something we
don't know? It's hard to say.
I've loved each of these trees and have grown and watched them with morbid
curiosity since I planted them when I was 11 (my parents thought I was
crazy asking for a tree for a birthday present), 12 (even more nuts), and
15 (certifiable), but I was lucky to live on a very large parcel of land
and I thought, 'If I can't have dinosaurs, I could at least have their
trees!'. A monkey puzzle will not live as far north as where I am sad to
say. The dawn redwood is my favorite because it is so genuinely beautiful.
The fronds are airy and bright green while the wood is dark red. In
autumn it is bronze and there is nothing like it. Pick one up! They grown
fast near a stream and once the roots reach the water, POW! you get up to
6' a year. The deer will eat it but it defends itself and has faced more
far, far, more dangerous predators...........
Hope this helps!! Any thoughts about dawn redwoods, gingkos, or umbrella
pines I'm happy to entertain (monkey puzzles too).