As it turns out, quite hard! I set out to reproduce this nice design:
It’s not just the mass of different shapes here, it is also the very subtle colours - just light shades of blue on some leaves, and very dark blue and green on others. Tracing it went well, and I painted a sketch on graph paper.
Then I ‘painted’ the result with watercolour pencils, just to see what it might look like:
Not toooo bad, I suppose. The tricky parts are the very slightly overlapping leaves, and the small details like the flowers or small vines. I’ve left some of these out, which is a shame as the contrast between the largest features (leaves, artichoke?) and the smallest is what makes this so good.