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How to use hydrangea fertiliser: rates and when to stop

Updated: October 2026

You already have a Vitax bag or a Westland tub, or you are about to follow a weekly line on a Topline bottle. The amazon.co.uk bullets, the Vitax label, and the Westland colourant label do not describe the same routine. This page keeps the feed rate and the colourant rate apart, says which number sits on the listing and which sits on the manufacturer label, and says when to stop. It does not rank the packs. The [hydrangea fertiliser comparison](/hub/fertiliser-soil-and-bark-mulch/hydrangea-fertiliser) is the product table. The gram figures below come from the manufacturer labels we cite, not from a lab of our own. A qualifying purchase can earn a commission at no extra cost to you.

You already have a Vitax bag or a Westland tub, or you are about to follow a weekly line on a Topline bottle. The amazon.co.uk bullets, the Vitax label, and the Westland colourant label do not describe the same routine.

Our top picks

Vitax Ltd Vitax hydrangea feed granules, 2 x 1 kg

Best overall

Vitax Ltd Vitax hydrangea feed granules, 2 x 1 kg
9.8/10about £11.98
View offer
Vitax Ltd Vitax hydrangea colourant, 500 g

Alternative

Vitax Ltd Vitax hydrangea colourant, 500 g
9.8/10about £8.48
View offer
Westland Westland hydrangea colourant, 500 g

Best value

Westland Westland hydrangea colourant, 500 g
9.4/10about £6.99
View offer
On this page
  1. 1.Use the label that matches the pack
  2. 2.Vitax hydrangea feed, spring and once more
  3. 3.Colourant on the soil, not the leaves
  4. 4.When to stop, and when to get help

Use the label that matches the pack

The amazon listing for the Vitax granules says planting and a spring top dressing. It does not print grams. The Vitax label does. The Westland colourant listing prints no dose and no eye warning. The manufacturer page does both. A feed is a planting dose and a spring top dressing, then at most one repeat. A colourant is a separate soil drench. Do not add the gram rates together, and do not invent a millilitre rate for the Topline liquid. A shop sheet that prints 4:2:6 or 4.5-2-7 is not on the amazon raw. If you have not decided to feed, read the hydrangea fertiliser buying guide first.

Vitax hydrangea feed, spring and once more

Use the Vitax Hydrangea Feed label, not the empty dose line on amazon. At planting, mix 70–140 g into the soil around the root ball. In spring, spread 70 g per square metre under the branches, and repeat after six to eight weeks if the plant still needs it. A gloved handful is about 35 g. Water it in if the soil is dry. Brush granules off leaves. Pots are smaller. About 30 cm across is about 5 g. About 38 cm is about 7.5 g. About 50 cm is about 15 g. The same label says this feed does not change flower colour. One reviewer says overfeeding killed young plants and that this was their own fault. If you wanted blue, this is the wrong pack. Plant limits are on how to turn hydrangeas blue.
Vitax Ltd Vitax hydrangea feed granules, 2 x 1 kg

Testsieger

Vitax Ltd Vitax hydrangea feed granules, 2 x 1 kg
9.8/10about £11.98
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Colourant on the soil, not the leaves

Westland’s own page, which the amazon bullets do not repeat, says April to September. Work 50 g per square metre into the soil. Then every seven days dissolve 50 g in 5 litres of water and apply it to the soil, not the leaves. One level capful is that 50 g. Pots start at 50 g per 5 litres of compost. On alkaline soil it says ericaceous compost or double the rate. Do not double a dose you have already doubled. The Vitax colourant is weaker. Its 250 g label is 1 part colourant to 30 parts compost at potting, then 30 g per 5 litres of water each week, dissolved first in a little hot water. That mix is about 15.3 percent aluminium sulphate, against about 93 percent for Westland. The two small listings say 30 ml per application and dilute first. Do not assume 30 ml equals 50 g in 5 litres.

When to stop, and when to get help

The RHS warning is soft growth that frost damages, not a calendar date. Do not treat the end of July as an RHS rule. Westland’s colourant window still runs to September, which is later than a cautious feed stop. A weekly nutrient liquid copied from that colourant schedule grows leaf at the expense of next year’s buds. If the leaves look burnt, stop. Do not apply another dose. A collapsed shrub or a whole chalk border is a soil lab or a professional. Westland’s safety data sheet prints +44 1480 443789. Rinse an eye, or call a poison centre if a child or a pet has swallowed the powder.

Common questions

How much Vitax feed do I put on in spring?
The Vitax label says 70 g per square metre under the branch spread, then again after six to eight weeks. At planting the range is 70–140 g. A gloved handful is about 35 g. The amazon listing does not print these grams.
How do I mix Westland colourant?
The manufacturer page says 50 g in 5 litres of water every seven days from April to September, on the soil, after 50 g per square metre worked in. The amazon bullets do not print this dose. Do not pour it on the foliage.
Can I pour colourant on the leaves?
No. Westland says the drench goes on the soil. UK reviews describe white marks when the mix hit the leaves. A foliar splash is not a faster route to blue. Keep the watering can at the base, and rinse leaves if you miss.
When do I stop?
Stop feeding while growth can still harden. The RHS does not give a calendar date. Colourant labels run to September. Do not treat the end of July as an RHS rule.
What if the plant looks burnt after the pack dose?
Stop. One Westland review says the stated pack amount nearly killed a plant. Do not apply a second dose. Get advice if the shrub collapses. A doubled dose on chalk is a soil-lab question.
Do I follow the amazon weekly line or the granule label?
Follow the label on the pack in your hand. The Vitax granule label is a spring rate and one repeat. A weekly line on a Topline liquid is a different product. Do not merge 70 g per square metre with 50 g in 5 litres.
What do I do if it gets in an eye?
Rinse and call a poison centre or a doctor. Westland’s safety data sheet prints +44 1480 443789. The Vitax colourant label warns of eye damage and skin irritation. The amazon bullets for these tubs often omit that text. Wear eye protection before you mix the powder.

Related pages

Hydrangea feed versus colourant

Hydrangea fertiliser

Best hydrangea fertiliser UK by the job, not the stars

How to turn hydrangeas blue on acid soil or in a pot

Hydrangea fertiliser buying guide: feed, colour or none

Sources

Public UK and maker sources from the research digest, used for this page in October 2026. Prices, stars and review counts are from the ten amazon.co.uk listings captured on 19 October 2026. Scores follow the 21 October 2026 shelf note. The NPK 8-4-12 line is the Vitax label, and it is not printed in the amazon bullets. Aluminium percentages and the eye-damage class are from the maker sheets named below, not from an amazon bullet. The March 2026 GOV.UK item was a consultation, not a shopping rule.

  1. RHS, shrubby hydrangea growing guide (retrieved 19 October 2026)
  2. RHS, acidifying soil (retrieved 19 October 2026)
  3. RHS, soil pH (retrieved 19 October 2026)
  4. Agriculture Act 1970, section 68 (retrieved 19 October 2026)
  5. Fertilisers Regulations 1991 (retrieved 19 October 2026)
  6. GOV.UK, new fertiliser regulations, 19 March 2026 (retrieved 19 October 2026)
  7. Vitax Hydrangea Feed label (retrieved 19 October 2026)
  8. Westland Hydrangea Colourant (retrieved 19 October 2026)
  9. Westland Hydrangea Colourant safety data sheet (retrieved 19 October 2026)