Sketch drawing contest #6 - trees

Here's my entry for @sparkyez Sketch Drawing Contest #6. The main rule is to stick to black pen or pencil - no colour! This is my kind of drawing, I love keeping it simple.

The theme is trees!!  🌴  🌴  Plants are amazing, they are way more dynamic than we give them credit. Check out these crazy facts about plants. I wanted to integrate an animal in my drawing, so decided to draw a turtle with a forest on its back. Here's my entry: 

As usual, I've stuck to a small piece of paper (approx 10x14cm). I started by looking at a few photos of tortoises online, did a rough outline in pencil, then added detail. Here are a few pictures showing the rest of process once I'd started drawing with a pen (I forgot to take pictures from the start...)