Repotting guide

When & how to repot Small-flowered alumroot (Heuchera micrantha)

Also called Small-flowered alumroot, Crevice alumroot, Small alumroot.

More about small-flowered alumroot

About Small-flowered alumroot

Heuchera micrantha · also called Small-flowered alumroot, Crevice alumroot · flowering

Small-flowered alumroot is a Pacific coast evergreen perennial native to moist, rocky cliffs and woodland slopes from British Columbia to California. It produces elegant wiry stems carrying tiny white to cream flowers over a long summer season above attractively lobed, often silver-veined, green to bronze foliage. This species is a key parent of many popular foliage Heuchera cultivars, including 'Palace Purple'.

Mature size: 30–50 cm tall (to 75 cm in flower) and 30–50 cm wide (12–20 in tall; to 30 in in flower)

Watch for — Vine weevil: Vine weevil larvae (white C-shaped grubs) feed on Heuchera roots, causing sudden collapse. Apply parasitic nematodes (Steinernema kraussei) in late summer/autumn as a soil drench to container and border plants. Inspect roots during division.

How to tell small-flowered alumroot needs repotting

Repotting on a calendar is less reliable than reading the plant. For small-flowered alumroot, 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 small-flowered alumroot) 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 small-flowered alumroot

Only every 2–4 years, when genuinely crowded. Small-flowered alumroot 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. Mound-forming, evergreen to semi-evergreen perennial with kidney-shaped to shallowly lobed leaves, often with silver or pale veining; very slender, branching flower scapes carry open panicles of tiny flowers.

What size pot to step small-flowered alumroot up to

Go up only one pot size — roughly 2–3 cm (about an inch) wider in diameter, no more. Small-flowered alumroot 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 small-flowered alumroot 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 small-flowered alumroot

Early spring, just as new growth restarts, is the ideal window for small-flowered alumroot. 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 small-flowered alumroot

Confirm it actually needs it. Slide small-flowered alumroot 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 small-flowered alumroot 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, moist, well-drained loam with good organic content; ph 5.5–6.5, 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 small-flowered alumroot 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 small-flowered alumroot

Small-flowered alumroot wants humus-rich, moist, well-drained loam with good organic content; ph 5.5–6.5. Naturally found in humus-enriched, slightly acidic rocky soils with excellent drainage. Amend garden soil with leaf mould or fine-grade bark. Unlike some Heucheras, this species prefers a slightly more acidic soil than neutral. Avoid heavy clay. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting small-flowered alumroot — frequently asked questions

How often should you repot small-flowered alumroot?

Only every 2–4 years, when genuinely crowded for small-flowered alumroot. Only repot small-flowered alumroot 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, moist, well-drained loam with good organic content; ph 5.5–6.5. The key mistake is over-potting: a too-big pot stays wet and rots the roots.

What size pot does small-flowered alumroot need?

When is the best time of year to repot small-flowered alumroot?

Does small-flowered alumroot like to be root-bound?

Yes — small-flowered alumroot 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 small-flowered alumroot after repotting?

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