Organism of the week #16 – From tiny acorns do mighty oaks grow

There’s something very satisfying about growing plants from seed, and none more so than growing a monster from next-to-nothing:

Sequoiadendron giganteum eighteen months old [CC-BY-SA-3.0 Steve Cook]

Sequoiadendron giganteum, eighteen months old

At the moment, this little redwood seedling is just 18 months old. Given 500 years or so, it’s going to get a wee bit bigger:

Sequoia sempervirens in California [CC-BY-2.0 Alex Lomas]

Somewhat more elderly Sequoia sempervirens in Muir Woods

The seeds of redwoods are absolutely titchy, as you can’t see in the picture, below because the idiot who took the photo forgot to put a scale bar on it. Each seed has a mass of about 5 milligrams.

Sequoia sempervirens strobili and seeds [CC-BY-SA-3.0 Steve Cook]

Sequoia sempervirens strobili and seeds

The adult trees are about 70 m in height (h), with a girth at ground-level of about 10 m, hence a radius (r) of 10/2π = 1.6 m. Modelling them thoroughly inaccurately as big cones of water, which has a density (ρ) of 1 tonne per cubic metre, means a typical redwood tree has a mass (M) of about:

M = ⅓ πr² h ρ = ⅓ π × 1.6² × 70 × 1 = 187 t

This is as much as a blue whale, but much larger specimens exist, so this is a conservative estimate of just how astonishingly massive these trees can become.

These trees take about 1000 years to get to this size, which is about 32 billion seconds:

1000 × 365 × 24 × 60 × 60 = 31 536 000 000 s

The trees won’t be growing at a constant rate for their entire life-span, but if we pretend they do (as anything cleverer is beyond my patience), then these trees would put on about 6 milligrams of mass per second:

187 000 000 g / 31 536 000 000 s = 0.006 g s⁻¹

Satisfyingly, this means that if you were to plant one redwood seed, and then spend the next thousand years adding redwood seeds to a pile, one every second, then the tree and the pile would have the same mass by the end of the millennium.

I’m all about the practical gardening tips.

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