Repotting guide

When & how to repot Geranium nodosum (Geranium nodosum)

Also called Knotted cranesbill, Knotted geranium.

More about geranium nodosum

About Geranium nodosum

Geranium nodosum · also called Knotted cranesbill, Knotted geranium · flowering

Knotted cranesbill is a tough, shade-loving European woodland perennial with glossy, three-to-five-lobed leaves and long-lasting funnel-shaped flowers in pink to lilac-purple, often faintly veined, from late spring well into autumn. One of the best hardy geraniums for dry shade, it spreads gently, copes under trees and dies back in winter.

Mature size: Typically 30-50 cm tall and 50-60 cm wide, spreading further over time

How to tell geranium nodosum needs repotting

Repotting on a calendar is less reliable than reading the plant. For geranium nodosum, watch for these signs:

Roots spiralling thickly out of the drainage holes or pushing the whole plant up out of the pot.
The pot is so packed that water runs straight through in seconds and barely wets the soil.
It has split a plastic pot, or the rootball is a solid mass with almost no soil left when you slide it out.
Growth and (for geranium nodosum) flowering have clearly stalled despite good light and feeding — but remember this plant likes being snug, so a little crowding alone is not a reason to repot.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot geranium nodosum

Only every 2–4 years, when genuinely crowded. Geranium nodosum is one of the plants that genuinely prefers a snug pot — it grows and flowers better with its roots a little restricted, so resist the urge to repot it on schedule. Clump-forming herbaceous perennial that spreads steadily by rhizomes and self-seeding to form effective groundcover. Produces glossy lobed foliage with airy, branching flower stems; deciduous, dying back to the crown in winter..

What size pot to step geranium nodosum up to

Go up only one pot size — roughly 2–3 cm (about an inch) wider in diameter, no more. Geranium nodosum positively prefers a snug pot: it flowers and grows better when the roots are a little restricted. The single biggest repotting mistake here is over-potting — dropping geranium nodosum into a pot two or three sizes up. All that surplus soil holds water the small root system cannot use, stays cold and wet, and rots the roots within weeks. When in doubt, choose the smaller pot.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot geranium nodosum

Early spring, just as new growth restarts, is the ideal window for geranium nodosum. The plant is moving into its strongest growth phase and re-roots into fresh soil quickly. Avoid repotting in winter dormancy or, for flowering plants, while it is in bud or bloom — recovery is slowest then and you risk dropping the flowers.

Step-by-step: repotting geranium nodosum

Confirm it actually needs it. Slide geranium nodosum out and check the roots. Only continue if it is genuinely packed — this plant prefers a snug pot, so if there is still soil and room, put it straight back.
Pick a pot only one size up. Choose a pot just 2–3 cm wider with good drainage. Resist anything bigger; over-potting is the main killer here.
Ease it out gently. Water lightly the day before, then tip geranium nodosum out, supporting the base. Tease the outer roots free only enough to stop them circling.
Repot at the same depth. Add a layer of fresh humus-rich, moisture-retentive loam, tolerant of poorer soils, set the plant so the soil line sits exactly where it did before, and backfill around the sides, firming lightly.
Settle it in. Water once to settle the soil, then let it sit. Hold off on more water until the top of the soil dries — fresh soil around a small root system stays wet for a while.

Aftercare

Because the new soil holds more water than the old crammed rootball did, ease right back on watering — let the top of the soil dry before you water geranium nodosum again, or you will rot the roots in the very pot you just moved it to. Keep it out of harsh direct sun for a fortnight. Do not fertilise for about 4 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for geranium nodosum

Geranium nodosum wants humus-rich, moisture-retentive loam, tolerant of poorer soils. Best in fertile, organic woodland soil, but adapts to a wide range including drier, root-filled ground beneath trees. Tolerates most pH levels; avoid waterlogged sites. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting geranium nodosum — frequently asked questions

How often should you repot geranium nodosum?

Only every 2–4 years, when genuinely crowded for geranium nodosum. Only repot geranium nodosum every 2–4 years, and only when it is genuinely root-bound — it flowers and grows best slightly crowded. Step up just one pot size in spring using humus-rich, moisture-retentive loam, tolerant of poorer soils. The key mistake is over-potting: a too-big pot stays wet and rots the roots.

What size pot does geranium nodosum need?

When is the best time of year to repot geranium nodosum?

Does geranium nodosum like to be root-bound?

Yes — geranium nodosum genuinely flowers and grows best when slightly pot-bound, so do not rush to repot it. The mistake to avoid is over-potting into a much larger pot: the excess soil stays wet, the roots cannot use it, and the plant rots. Only repot every few years and only one snug size up.

Should you fertilise geranium nodosum after repotting?

Not immediately. Wait about 4 weeks after repotting geranium nodosum. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.