Dynamic accumulators are plants with extensive root systems which bring up nutrients from deep in the soil where other plants can’t access them. The top growth is regularly cut and can be added to the compost heap, used to make nutrient tea, or simply left on the ground as mulch.
I’m growing comfrey and yarrow specifically as accumulators, but I’m pleased to note lemon balm, borage and bracken on the list as I have them growing as well. I use lemon balm for herbal teas and I grow borage for the bees—they love the bright blue flowers. Bracken grows all over our bush block and I’ve known for some time that it accumulates potassium. I put it through the mulcher and use it for compost and mulch.
I’m establishing yarrow under all my fruit trees and I’ve put comfrey at low points in the garden to mop up any nutrients that might be wanting to escape via run-off from vegetable beds. Last year I made a batch of nutrient tea by stuffing loads of comfrey into a 60 litre bin of water and letting it rot down (a bit smelly to begin with, but the plants loved it). The yarrow is flowering at the moment and attracting lots of tiny native insects as pollinators.
A word of warning with comfrey: don’t put it anywhere you need to be digging regularly; cut roots will sprout readily and it’s said to be very hard to get rid of. A single undisturbed clump will slowly increase in size.