Bigroot geranium in August: monthly care

Geranium macrorrhizum is evergreen and requires very little pruning, but a light tidy-up twice a year keeps it looking its best and encourages fresh growth. The main pruning window is March, just as new growth begins to emerge. Use garden shears or secateurs to trim back any tatty, winter-damaged, or browned foliage. You can be quite bold—cut the whole clump back by about half if it looks tired or sprawling. This rejuvenates the plant and makes way for the flush of aromatic new leaves and flower stems that follow in late spring. The second pruning opportunity is in August, after the main flowering period has finished. Deadhead spent flower stems by cutting them back to the base of the plant; this tidies the appearance and sometimes prompts a few late blooms. If the foliage has become leggy or untidy over summer, you can give it a light trim to neaten the mound, but avoid cutting back too hard in late summer as the plant needs some leaf cover going into autumn. Because this geranium spreads by rhizomes, you may occasionally need to lift and divide congested clumps or trim back edges that have crept beyond their allotted space. This is best done in early spring or autumn. Otherwise, pruning is minimal—far more important is the removal of any dead leaves in spring and the occasional shear to keep the evergreen mat dense and healthy.

Once established, Geranium macrorrhizum is remarkably undemanding. Its low water requirement means you rarely need to irrigate except during prolonged summer drought, and even then it will usually recover without intervention. Newly planted specimens benefit from watering during their first spring and summer if rainfall is scarce, but after that the rhizomes store moisture efficiently. Feed lightly in March or April with a general-purpose granular fertiliser such as blood, fish and bone or a balanced slow-release feed scattered around the base of the clump. Avoid high-nitrogen feeds, which promote soft, lush growth at the expense of flowers. One feed per year is sufficient; this is not a hungry plant. A top-dressing of garden compost or leaf mould in early spring also helps, especially on poorer soils, and doubles as a mulch to suppress weeds. Geranium macrorrhizum is fully hardy (zone 4–8) and needs no winter protection in temperate Europe. Its evergreen foliage persists through winter, though it may look a little battered by March—simply trim it back as described in the pruning section. Pests and diseases are rare. Occasionally vine weevil larvae may nibble the rhizomes, causing wilting; check for them if plants decline unexpectedly. Powdery mildew can appear in dry summers on congested clumps, but good air circulation and avoiding overhead watering usually prevent it. Otherwise, this geranium is trouble-free, spreading steadily to form fragrant, weed-proof ground cover with minimal input from you.