Pruning Bigroot geranium
When and how — Geranium macrorrhizum
Prune your bigroot geranium in March and August — the optimal month is usually August.
The next pruning window is August.
When to prune?
The perennial bigroot geranium is pruned in March and August.
With perennials, pruning is really seasonal management.
You don't prune perennials the way you prune shrubs. The work happens at three moments: (1) deadheading spent flower stems during the season to encourage repeat bloom, (2) optionally cutting back to about 10–15 cm above ground in late autumn, and (3) clearing all the old foliage in March before the new shoots emerge. Many gardeners now deliberately leave the old growth standing through winter — it protects the crown and shelters overwintering insects. Which approach to choose depends on taste and species: evergreen perennials (hellebore, bergenia) look better left alone, while wet-rotting species (hosta) need to come down after the first frost.
How to prune bigroot geranium
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.
Common mistakes
✗ Cutting back too early in spring
Late frost can still strike and the old foliage protects the crown. Wait until the first new shoots are visible (usually mid-March) — then you know the season has actually started.
✗ Skipping deadheading
Hardy geranium, salvia, lupin and delphinium will give a second flush if you cut spent stems back to just above a pair of healthy leaves as soon as the first flowers fade.
✗ Cutting ornamental grasses down in autumn
The dry stems are the whole point of winter interest, AND they protect the crown from frost and waterlogging. Cut down to a fist's height only in late February.
Combine with feeding
In March you can combine pruning with feeding — efficient, and you only disturb the plant once. Read the full care guide for bigroot geranium →
Hold off on pruning
Better to wait than prune at the wrong moment. The next optimal window is August. Until then: leave the plant alone — only remove dead or diseased wood (which you can do year-round).
