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Multi purpose compost vs seed compost

Updated: October 2026

You have a packet of seed, a bullet that says the bag is fine for seeds, and a doubt about whether that bag is seed compost. This page compares multi purpose compost vs seed compost, then applies the difference to the five bags on the [compost soil comparison](/hub/fertiliser-soil-and-bark-mulch/compost-soil). The recommendation has a condition: stay with these multi-purpose bags for containers and for potting on, and buy a seed compost when the seed is fine or the bag in front of you is coarse. None of the five listings prints an NPK, so this page does not claim that any of them is high in feed.

You have a packet of seed, a bullet that says the bag is fine for seeds, and a doubt about whether that bag is seed compost.

Our top picks

Munnie Munnie multi-purpose compost 60 L

Best overall

Munnie Munnie multi-purpose compost 60 L
8.0/10about £9.34
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Growmoor Growmoor multi-purpose compost 50 L

Rank 2

Growmoor Growmoor multi-purpose compost 50 L
8.5/10about £9.25
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Growmoor Growmoor multi-purpose compost 180 L

Alternative

Growmoor Growmoor multi-purpose compost 180 L
6.8/10about £30.00
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On this page
  1. 1.Two jobs, two mixes
  2. 2.What these bags claim about seeds
  3. 3.When multi-purpose is enough
  4. 4.When to buy seed compost instead

Two jobs, two mixes

Seed compost is milled fine and kept low in nutrients so that a small seed can push through and a young root is not sitting in a strong feed. Multi-purpose compost is the coarser, usually richer mix for plants that are already growing, and for pots you will plant with something that has roots. BBC Gardeners’ World is more permissive on the first step. Its indoor sowing guide says a multi-purpose compost is fine for most seeds, and that some very small seeds may still need a seed compost. Both can be true together: many larger seeds tolerate a multi-purpose bag, and fine seed is where a seed compost earns its place.

What these bags claim about seeds

Growmoor’s bullets put seeds, cuttings, and seed compost in the same line as containers, beds, and baskets. A fine texture in a review is not a seed grade, and the shared review texts also mention lumps. Munnie’s title says seed compost, and the bullets talk about germinating seeds. Laeto’s bullets include seed sowing.
Munnie Munnie multi-purpose compost 60 L

Testsieger

Munnie Munnie multi-purpose compost 60 L
8.0/10about £9.34
View offer

When multi-purpose is enough

Stay in this set when the plant is already a plant. Potting on a tomato, a basil, or a bedding plant into a patio pot is the job multi-purpose compost is sold for. The RHS points you to multi-purpose once seedlings are large enough to handle. Larger seeds are the other stay case. Peas, beans, and squash are the examples the RHS peat-free sowing notes treat as less fussy. Gardeners’ World’s “most seeds” line points the same way for anything that is not tiny. Munnie reviews that mention peas from seed fit that stay case. If the bag you open is fine and moist, you can sow those larger seeds in it and accept that you are using a multi-purpose compost, not a tested seed grade.

When to buy seed compost instead

Leave this category when the seed is fine. Lobelia, begonia, and similar small seed are where Gardeners’ World and the RHS both point you to a seed compost. A lumpy or woody bag will bury that seed even if a bullet says seed compost. Leave as well when the bag will not wet. Gardeners’ World warns that soil-less compost can fail to rewet once it dries, which matches the Growmoor 180 litre reviews. Those reviews are a handling problem, not a seed grade. Wetting a dry sack is on how to use multi purpose compost. Buy a compost sold as seed compost when the seed is fine or the multi-purpose bag is coarse.

Common questions

Can I sow seeds in multi-purpose compost?
You can sow many larger seeds in it. Gardeners’ World says multi-purpose is fine for most seeds, while the RHS prefers a seed compost for sowing and multi-purpose after the seedlings are established. Peas, beans, and squash are the less fussy cases. Fine seed is the case for leaving this set. None of these bags prints the nutrient level that would settle the argument.
When is seed compost the better buy?
Buy seed compost when the seed is very small or the bag you have is coarse, woody, or dry enough to shed water. Seed compost is milled finer and sold as lower in feed. These five listings claim seeds in the bullets and do not show an analysis, so they are not a substitute specification. The extra purchase is justified for a tray of fine seed, not for potting on a plant that already has roots.
Does a bullet that says seed compost make the bag seed compost?
No. Growmoor puts seed compost in a bullet next to baskets and borders. Munnie uses the words in the title. Laeto says seed sowing. A seed compost is defined by a fine milling and a low feed, which these listings do not document. The bullet is a job list. The bag you open may still be lumpy.
What about larger seeds such as beans and peas?
They are the seeds most likely to tolerate this set. The RHS treats peas, beans, and squash as less fussy than fine seed, and Munnie reviews include peas sown in that compost. You are still using a multi-purpose bag with no printed analysis. If the sack is the smelly, woody Laeto pattern, even a bean is better in a different mix.
When do I move seedlings into multi-purpose compost?
Move them when they are large enough to handle, or when roots show at the base of the module, which is the RHS timing. That is the point of these bags: containers and potting on, not the first day of a fine-seed tray. A 50 litre sack is enough for a small pricking-out session. The 180 litre title is a lot of compost for a windowsill.
Will a fine Growmoor bag replace a seed compost?
Not as a grade. Reviewers describe a very fine mix used for seeds, and they also describe lumps. You could sieve a little for a trial tray and accept the unknown feed. Do not treat the shared 4.5 from 7,425 as proof of a seed compost, and do not spread the bag on the beds. The RHS says potting compost stays in containers.

Related pages

Compost soil buying guide

Peat-free compost soil

Compost soil

Best multi purpose compost in this amazon.co.uk set

How to use multi purpose compost in pots and baskets

Sources

Public UK sources from the research digest, used for this page in October 2026. Prices, stars and review counts are from the five stored amazon.co.uk listings. A later view of the 50 litre Growmoor listing on 19 October 2026 differed; the table keeps the stored figures. Peat-free, organic and volume lines are seller claims unless a review contradicts them. This is not a laboratory test.

  1. RHS, peat-free compost choices (retrieved 19 October 2026)
  2. RHS, peat-free compost for seeds and cuttings (retrieved 19 October 2026)
  3. RHS, John Innes compost (retrieved 19 October 2026)
  4. Defra, horticultural peat announcement, 27 August 2022 (retrieved 19 October 2026)
  5. Defra written answer on the peat ban, 12 September 2024 (retrieved 19 October 2026)
  6. Horticultural peat bill, Parliament (retrieved 19 October 2026)
  7. Public Health Scotland, gardening safely (retrieved 19 October 2026)
  8. RHS, minimising health risks in the garden (retrieved 19 October 2026)