In reply to GrahamUney:
Yes - heather is totally bomber
Grass - very seasonal and difficult to get enough in your hand to give a reliable handheld, I generally 'dig' my fingers into the dirt if possible (thistles are pointless, bit like vegetable midges)
Woodruff (I'd forgotten the name) promises so much delivers so little.
Braken- hated on here, but it's reliable, pretty sure you could belay off it, a la snow bollard, must add never tried that, great for descending, much better than bare wet grass January through to March