How to make hydrangeas pink
Pink hydrangeas need soil near neutral. Lime gets you there.
Mophead and lacecap hydrangeas flower pink when the soil is near neutral, from about pH 6.5, because aluminium is locked up and the roots cannot take it in. Below about 5.5 they turn blue; in between, mauve. Raising the pH with Granulated Lime is the fix; expect the colour to shift over one or two flowering seasons.
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- Only mophead and lacecap types change colour. White varieties stay white.
- Test first. Aim for about 6.5 to 7.0; above 7.5 leaves start to yellow.
- In pots, use multipurpose compost rather than ericaceous, and water with tap water.
How much lime
| Where | Rate | When |
|---|---|---|
| New border at pH 6.0 | 0.4 kg (sand) to 0.6 kg (clay) per m² | Dug in, autumn to early spring |
| New border at pH 5.5 | 0.7 kg (sand) to 1.0 kg (clay) per m² | Half dug in, half on the surface |
| New border at pH 5.0 | 1.0 kg (sand) to 1.4 kg (clay) per m² | Half dug in, half on the surface |
| Established hydrangea | 30 to 50 g/m² per half pH unit over the root area | Late winter or early spring; rake in lightly, retest in six to eight weeks and repeat to the test |
New borders: RHS liming table, dug into the top 20 cm to bring the soil to about pH 6.5. Established shrubs: our Granulated Lime top-dressing rates, sand to clay. Scatter rather than dig near established roots, and retest before repeating.
Work out your exact amount. Enter your area, your test reading and your soil type, and the calculator gives the dose, the timing and the bags to buy.
Keeping them pink
- No ericaceous compost. It is acid by design, so it pulls the pH down where you use it.
- Tap water is fine. Hard tap water adds a little lime with every can, which helps here.
- No hydrangea colourant. Those are aluminium sulphate, the blueing agent.
- Retest each spring. Lime again only if it has dropped below 6.5.
Common questions
How long does it take to turn hydrangeas pink?
Lime starts shifting the pH at the surface within weeks, but the plant still holds aluminium. Expect a mauve stage and a full change over one or two flowering seasons.
How do I make hydrangeas pink naturally?
Lime is natural: Granulated Lime is ground limestone, calcium carbonate, bound into granules. Wood ash also raises pH but is less predictable.
Why have my pink hydrangeas turned blue?
The pH has dropped, often after a switch to rainwater, a dressing of ericaceous compost, or as the acid soil underneath reasserts itself. Retest and lime to the rate for your reading.
Can I turn a blue hydrangea pink in acid soil?
In the ground on strongly acid soil it is a constant battle. Growing it in a pot of limed multipurpose compost is easier.
More: Granulated Lime · soil pH calculator · how to make hydrangeas blue · how to test soil pH · how to raise soil pH
Pink starts in the soil
About 98% calcium carbonate in granules that fall back to fine lime when wet. 30 to 50 g/m² per half unit around established hydrangeas.
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Free UK delivery over £40. Buy now goes straight to checkout.
Free UK delivery over £40. Dispatched in 1 to 2 working days. Packed and posted from Stockport.