Repotting guide

When & how to repot Lacecap Hydrangea (Hydrangea macrophylla 'Mariesii Perfecta')

Also called lacecap hydrangea, Blue Wave hydrangea.

More about lacecap hydrangea

About Lacecap Hydrangea

Hydrangea macrophylla 'Mariesii Perfecta' · also called lacecap hydrangea, Blue Wave hydrangea · flowering

'Mariesii Perfecta', long sold as Blue Wave, is a classic lacecap hydrangea with flat flowerheads of tiny fertile florets ringed by showy sterile sepals. Flowers turn blue on acidic soil and pink on alkaline. It is a rounded deciduous shrub for part shade, blooming on old wood in summer, and prefers moist, fertile soil.

Mature size: Around 1.2-1.8 m tall and wide at maturity, forming a broad mounded shrub.

Watch for — Powdery mildew and leaf spot: Fungal patches appear in humid, crowded conditions. Improve airflow, avoid overhead watering late in the day, and remove badly affected leaves.

How to tell lacecap hydrangea needs repotting

Repotting on a calendar is less reliable than reading the plant. For lacecap hydrangea, 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 lacecap hydrangea) 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 lacecap hydrangea

Only every 2–4 years, when genuinely crowded. Lacecap Hydrangea 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. Rounded, bushy deciduous shrub with broad mid-green leaves; flowers on the previous season's wood (old wood) in mid to late summer..

What size pot to step lacecap hydrangea up to

Go up only one pot size — roughly 2–3 cm (about an inch) wider in diameter, no more. Lacecap Hydrangea 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 lacecap hydrangea 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 lacecap hydrangea

Early spring, just as new growth restarts, is the ideal window for lacecap hydrangea. 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 lacecap hydrangea

Confirm it actually needs it. Slide lacecap hydrangea 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 lacecap hydrangea 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 moist, fertile, humus-rich, free-draining loam, 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 lacecap hydrangea 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 lacecap hydrangea

Lacecap Hydrangea wants moist, fertile, humus-rich, free-draining loam. Wants moisture-retentive yet well-drained fertile soil. Soil pH governs flower colour: acidic soil (low pH, with available aluminium) gives blue, alkaline soil gives pink, and intermediate pH yields purple-mauve. Add ericaceous compost or sulphur to push blue. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting lacecap hydrangea — frequently asked questions

How often should you repot lacecap hydrangea?

Only every 2–4 years, when genuinely crowded for lacecap hydrangea. Only repot lacecap hydrangea 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 moist, fertile, humus-rich, free-draining loam. The key mistake is over-potting: a too-big pot stays wet and rots the roots.

What size pot does lacecap hydrangea need?

When is the best time of year to repot lacecap hydrangea?

Does lacecap hydrangea like to be root-bound?

Yes — lacecap hydrangea 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 lacecap hydrangea after repotting?

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