When you got in the car today, what did you do? You cranked it up and pressed the pedal down to get up to speed. But once you get going, it’s easy to keep the car at the speed limit (you were going the speed limit, right?). Just a little constant pressure on the pedal – a little constant infusion of energy – is all it takes.
But if you have a big obstacle in your way (like tough terrain or a hill), the car takes more energy to maintain speed. If you let the car slow down, it requires extra energy to get back to that constant speed.
Trees may not take you places, but their energy consumption is not dissimilar to the vehicle that brings you to them. A tree needs an extra surge of power at the start of its journey, but once it’s maintaining a steady growth rate, all you need to do is provide a little steady care.