Repotting guide

When & how to repot King of Hearts Brunnera (Brunnera macrophylla 'King of Hearts')

Also called King of Hearts Siberian bugloss.

More about king of hearts brunnera

About King of Hearts Brunnera

Brunnera macrophylla 'King of Hearts' · also called King of Hearts Siberian bugloss · flowering

King of Hearts is a robust Siberian bugloss with large, heavily frosted silver leaves veined and edged in green, giving strong all-season shine in shade. Sprays of small blue forget-me-not flowers appear in spring. This clump-forming woodland perennial is more sun- and heat-tolerant than green forms but still needs cool, evenly moist soil.

Mature size: 30-40 cm tall and 45-60 cm wide.

How to tell king of hearts brunnera needs repotting

Repotting on a calendar is less reliable than reading the plant. For king of hearts brunnera, 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 king of hearts brunnera) 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 king of hearts brunnera

Only every 2–4 years, when genuinely crowded. King of Hearts Brunnera 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. Vigorous, clump-forming herbaceous perennial forming a dense mound of broad silver basal leaves, with sprays of blue flowers on wiry stems in mid to late spring..

What size pot to step king of hearts brunnera up to

Go up only one pot size — roughly 2–3 cm (about an inch) wider in diameter, no more. King of Hearts Brunnera 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 king of hearts brunnera 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 king of hearts brunnera

Early spring, just as new growth restarts, is the ideal window for king of hearts brunnera. 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 king of hearts brunnera

Confirm it actually needs it. Slide king of hearts brunnera 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 king of hearts brunnera 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, well-drained loam (ph 6.0-7.5), 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 king of hearts brunnera 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 king of hearts brunnera

King of Hearts Brunnera wants humus-rich, moisture-retentive, well-drained loam (ph 6.0-7.5). Work in leaf mould or compost for a woodland feel. Tolerates heavier soils if drainage is adequate; avoid waterlogging the crown, and avoid thin dry soils that trigger scorch. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting king of hearts brunnera — frequently asked questions

How often should you repot king of hearts brunnera?

Only every 2–4 years, when genuinely crowded for king of hearts brunnera. Only repot king of hearts brunnera 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, well-drained loam (ph 6.0-7.5). The key mistake is over-potting: a too-big pot stays wet and rots the roots.

What size pot does king of hearts brunnera need?

When is the best time of year to repot king of hearts brunnera?

Does king of hearts brunnera like to be root-bound?

Yes — king of hearts brunnera 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 king of hearts brunnera after repotting?

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