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Compost for flowers buying guide

Updated: October 2026

You have a patio pot or a window box to fill, and the bag has to match that job before the price does. A compost for flowers buying guide starts with how long the plant stays, then the peat words, then the litres you can check. Heap compost from a bin is a soil improver for open ground. Bagged potting compost is what goes in the container. The [Flowers compost comparison](/hub/fertiliser-soil-and-bark-mulch/flowers-compost) lists seven amazon.co.uk multi-purpose bags, with shelf prices in GBP from those listings on 21 October 2026. We did not run a lab trial.

You have a patio pot or a window box to fill, and the bag has to match that job before the price does.

Our top picks

Munnie Munnie multi-purpose compost 60 L

Best overall

Munnie Munnie multi-purpose compost 60 L
8.1/10about £9.34
View offer
GROWMOOR Growmoor multi-purpose compost 50 L

Preis-Tipp

GROWMOOR Growmoor multi-purpose compost 50 L
8.0/10about £9.25
View offer
Miracle-Gro Miracle-Gro peat-free compost 20 L

Rank 3

Miracle-Gro Miracle-Gro peat-free compost 20 L
8.6/10about £7.95
View offer
On this page
  1. 1.What the bag is for
  2. 2.Type before brand
  3. 3.Litres, peat wording and feed
  4. 4.Weight and what to leave
  5. 5.Which check comes first

What the bag is for

Potting compost and a garden heap solve different problems. The heap is for a bed. A retail bag is the mix you tip into a pot. Spreading it on a border wastes a product priced by the litre. Every kept listing here is multi-purpose or potting compost, and none prints an NPK. Who each bag is for sits on the best compost for flowers page.

Type before brand

The RHS splits container compost by the stay. One-season bedding can use peat-free multi-purpose. A plant that stays for years is pointed at peat-free John Innes No. 3. Acid-loving plants want ericaceous compost. Seed wants a finer mix, then you pot on. John Innes is a recipe name, not a legally binding standard. None of these seven listings is John Innes or ericaceous. Buy the type for the stay first.
Munnie Munnie multi-purpose compost 60 L

Testsieger

Munnie Munnie multi-purpose compost 60 L
8.1/10about £9.34
View offer

Litres, peat wording and feed

Four checks sit on the listing: litres that agree, the words peat-free if that is what you came for, a printed feed window, and a weight you can carry. Only Miracle-Gro prints peat-free here, with a feed of up to 3 months. Growmoor 60 litres is about £13.98 and 14 kg. Munnie is about £9.34 at 60 litres, about 16p a litre only if the price is one bag, because the packs field says 2. Laeto is 120 litres at about £24.99, and some reviews describe 40 litre bags. DIVCHI claims 10 litres at about £7.70, listed at 680 g, and in the Amazon reviews it is a compressed block. The CB Fuels listing is about £21.71, with 2 × 60 litres in the title and 60 litres in the volume field, so there is no single pence-per-litre figure. The England timetable is on peat-free compost for flowers.

Weight and what to leave

A 12 to 15 kg sack is awkward on a bus. Miracle-Gro at 6.15 kg is the lightest loose bag. A smaller peat-free bag can still be the right buy when a larger sack is cheaper per litre.

Which check comes first

If the flowers are out by autumn, match peat-free multi-purpose, then litres that agree. If the plant stays for years, this set is the wrong shelf. A lower pence per litre only wins when you can lift the sack.

Common questions

Is multi-purpose compost the right bag for summer flowers in pots?
For bedding and baskets that last one season, the RHS points you at peat-free multi-purpose compost. Every bag in this set is multi-purpose or potting compost, and only the Miracle-Gro 20 litre listing prints peat-free. A shrub you will keep for years, or an acid-loving plant, wants a loam-based or ericaceous mix. None of these seven is John Innes or ericaceous. Match the stay first, then the words on the bag.
How many litres does a patio pot actually hold?
Love The Garden, a brand guide rather than a British Standard, lists about 5 litres for a 22 cm pot, 10 litres for 28 cm, 15 litres for 32 cm, 23 litres for 37 cm, and 33 litres for 42 cm, filled about 2 cm below the rim. Other calculators disagree, so treat the figures as a sketch. A 20 litre bag then covers roughly two 28 cm pots. Measure the pot if the rim is oval or the sides taper sharply.
Does organic or reduces peat use mean peat-free?
Those phrases are different claims. Peat-free is the sentence the listing has to print, and in this set only Miracle-Gro does that. Munnie says the blend enables less peat use. Laeto and DIVCHI use organic wording with no certifier named. The RHS advice is to treat a bag that does not say peat-free as peat-containing. A reduced-peat line can still include peat.
How long does the feed last if the bag says nothing?
Only Miracle-Gro states a window, up to 3 months, and you follow that line before you add more feed. The other six print no window and no NPK. Where a soil-less bag is silent, Gardeners’ World describes a fortnightly liquid feed from about six weeks for plants already in growth. Summer flowers then want a high-potassium liquid feed. That fallback is public advice, not a reading of these bags’ ingredients.
Is a cheaper large sack always better value than a 20 litre bag?
On these shelf prices Growmoor 50 litres is 18.5p a litre and Miracle-Gro 20 litres is about 40p, so the larger sack is cheaper per litre when the litres agree. It is still the wrong sack if you need the words peat-free, if you cannot lift 12 kg, or if the litre fields conflict. CB Fuels at £21.71 has no single pence-per-litre figure, because the title says 2 × 60 litres and the volume field says 60 litres.

Related pages

How to use flowers compost

Flowers compost

Best compost for flowers: match the bag to the job

Compost for hanging baskets: litres and daily water

Peat-free compost for flowers: England ban explained

Sources

Public UK sources from the research digest, used for this page in October 2026. Prices, stars and review counts are from the seven amazon.co.uk listings read on 21 October 2026. There is no laboratory test. Peat-free means the listing prints peat-free. An announced retail end date is not an Act. The Growmoor 50 litre and 60 litre review texts in this set are one shared sample.

  1. Defra, sale of horticultural peat to be banned (retrieved 21 October 2026)
  2. Written question 99957, 18 December 2025 (retrieved 21 October 2026)
  3. Deposited letter, 29 January 2026 (retrieved 21 October 2026)
  4. RHS, hanging baskets (retrieved 21 October 2026)
  5. RHS, growing plants in containers (retrieved 21 October 2026)
  6. RHS, peat-free tips (retrieved 21 October 2026)
  7. RHS, John Innes compost (retrieved 21 October 2026)
  8. RHS, minimising health risks in the garden (retrieved 21 October 2026)