Pruning Hemp Agrimony

Hemp agrimony requires very little pruning, but a single annual cut-back in March keeps plants tidy and encourages vigorous new growth. The stems die back naturally over winter, and the dried seed heads provide food for finches and other birds, so resist the temptation to tidy up in autumn. Leave the dead stems standing until late winter; they also offer shelter for overwintering insects. In March, before new shoots emerge, cut all the previous year's growth down to ground level using secateurs or a pair of sharp hand shears. The stems are hollow and quite brittle when dry, so they cut easily. Remove all the old material and add it to your compost heap, or leave small pieces on the soil surface as a light mulch if you prefer. If clumps become congested or outgrow their space after several years, March is also the time to lift and divide them. Dig up the entire root ball, split it into sections with a spade or two forks back-to-back, and replant the healthiest outer portions, discarding any woody central growth. This rejuvenates flowering and keeps plants compact. During the growing season, deadheading is not necessary unless you want to prevent self-seeding. Hemp agrimony can seed around freely in moist soil, which may be welcome in a wildlife or naturalistic planting but less so in a formal border. Snip off faded flower heads in late summer if you wish to limit spread. Otherwise, let the flowers mature into fluffy seed heads—they're attractive in their own right and highly valued by goldfinches.