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

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: 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. 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 π*r*² *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.