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Orchid bark buying guide: size, mix and true litres

Updated: October 2026

You have a moth orchid on a UK windowsill and a search page full of bags that all say fine. This orchid bark buying guide is the order to use before you compare prices: chip size first, then whether the bag is plain bark, bark with perlite, or a compost mix, then a litre figure you can believe. Stars come after that. The [orchid bark comparison](/hub/fertiliser-soil-and-bark-mulch/orchid-bark) holds the amazon.co.uk prices and review counts from the 20 October 2026 capture. Named picks sit on [best orchid bark](/hub/fertiliser-soil-and-bark-mulch/orchid-bark/sub/orchid-bark-best). Peter F. drew this from those listings and from public UK growing guides, with no lab trial. A qualifying purchase can earn a commission at no extra cost to you.

You have a moth orchid on a UK windowsill and a search page full of bags that all say fine.

Our top picks

UK GROW UK GROW bark and perlite 5 l

Best overall

UK GROW UK GROW bark and perlite 5 l
9.2/10about £9.99
View offer
Miracle-Gro Miracle-Gro peat-free orchid 10 l

Best value

Miracle-Gro Miracle-Gro peat-free orchid 10 l
9.0/10about £6
View offer
UK GROW UK GROW premium mix 20 l

Alternative

UK GROW UK GROW premium mix 20 l
8.8/10about £19.99
View offer
On this page
  1. 1.What grade the plant actually needs
  2. 2.Plain bark, perlite, or a compost mix
  3. 3.Litres you can believe
  4. 4.What the review count is really counting

What grade the plant actually needs

Melcourt's professional medium bark is pine at about 5–15 mm, with a pH around 5.0–5.5 and negligible nutrients. That is a grower's specification, not a promise that a retail pouch matches the same sieve. On the amazon.co.uk titles in this capture, fine is not one grade. One UK GROW line is titled 3–15 mm and fine grade, including the 10 litre bag at about £12.99. Another is titled 8–15 mm and also fine grade, at about £14.99. Reviewers of the 3–15 mm line described flakes that hold water, and pieces over the stated 15 mm maximum. Watering for this genus is on orchid bark for Phalaenopsis.

Plain bark, perlite, or a compost mix

Plain potting bark is chips and air. Melcourt states negligible nutrients on its pine bark, so you still feed a moth orchid yourself. A title that also says soil or compost is a different product. The UK GROW premium line uses bark and soil compost in the same listing, and one bullet says peat, soil, or very small bark can kill an orchid by holding water. Miracle-Gro's 10 litre peat-free orchid compost claims large pine pieces plus 11 nutrients. Peat-free on a label is a claim about that bag. Selling peat compost is not already illegal in England. Defra announced a retail ban aimed at 2024, and the Royal Horticultural Society says the legislation is not in place.
UK GROW UK GROW bark and perlite 5 l

Testsieger

UK GROW UK GROW bark and perlite 5 l
9.2/10about £9.99
View offer

Litres you can believe

Prices here are the 20 October 2026 amazon.co.uk capture, not a live quote. Miracle-Gro at about £6 for 10 litres is about £0.60 per litre, because the volume and the unit count both say 10 litres. Mid-range plain bark was about £13 to £17 for bags titled 10 to 20 litres. The 1 litre perlite pack at about £7.99 is about £8 per litre. The bark-and-perlite pouches list a unit count of 1.0 gram, which cannot be the fill. Leave a shelf price undivided when the title litres and the unit count disagree.

What the review count is really counting

A star line is only as wide as the sample behind it. The premium sizes, 5 litres at about £9.99 and 20 litres at about £19.99, both show 4.4 from 941 reviews, one parent listing. The bark-and-perlite sizes at 1, 2 and 5 litres all show 4.5 from 395 reviews, again one sample. The 3–15 mm 10 litre bag and the one titled 20 litres share 4.3 from 96 reviews. Nine reviews at 4.5, on the Elite 10 litre bag at about £12.99, cannot outweigh 160 reviews at 4.5 on Miracle-Gro. Seventeen reviews at 4.0 on the Black Soil Society mix are enough to read, not a settled verdict. How to get the old compost out, including a moss plug, is on how to repot with orchid bark.

Common questions

What chip size should I buy for a moth orchid?
Gardeners' World points moth orchids and cymbidiums towards about 8–15 mm, and finer-rooted orchids towards about 5–8 mm. For a typical UK shop moth orchid, start with the larger of those two bands and look at the chips before you soak them. A title that only says fine does not tell you which band is in the sack. If the pieces collapse into flakes, they will hold water the way old compost does.
Is fine on the bag the same as 5–8 mm?
In this amazon.co.uk capture it is not. One title uses fine for 3–15 mm and another uses fine for 8–15 mm. Specialist shops more often reserve fine for about 5–8 mm and medium for about 8–15 mm. Treat the millimetre range, when it is printed, as the fact, and treat fine as marketing. If no range is printed, the only check is the handful you tip out.
Do I need perlite already mixed in?
Perlite adds air and does not feed the plant. You can buy it mixed, as on the UK GROW bark-and-perlite pouches, or add it yourself to plain bark. A ready mix is convenient for one windowsill plant. Skip it if you wanted inert chips only, or if the title also leans on soil and compost wording you are trying to leave behind. Rinse dust either way if the bag looks powdery.
How many litres for one plant versus a small collection?
One moth orchid in a pot of about 12 cm needs a 2 litre or 5 litre bag, with spare bark kept sealed. Ten litres is the scale of several small pots. Miracle-Gro says its 10 litre bag fills six 12 cm pots or one 22 cm pot. A 20 litre sack is for a collection you will repot over a season. Extra bark in a pot that is too big stays wet.
What if the title says 20 litres and the details say 10 litres?
Do not calculate a price per litre. In this capture the plain bark titled 20 litres at about £16.99 and the one titled 20 litres at about £14.99 both show a unit count of 10 litres. One reviewer who expected 10 litres on the 8–15 mm listing measured under 6 litres with a 2 litre jug. Open the bag, or choose a listing where the volume and the unit count already agree, such as Miracle-Gro at 10 litres.

Related pages

Orchid bark versus sphagnum moss

Orchid bark

Best orchid bark UK when the review counts are shared

Phalaenopsis bark mix for a clear pot and dry-down

How to repot orchid bark without a pot that stays wet

Sources

Public UK sources from the research digest, used for this page in October 2026. Prices, stars and review counts are from the eleven amazon.co.uk listings captured on 20 October 2026. A peat-free, sterilised or organic line is a listing claim unless a certificate number is printed. No laboratory test was run.

  1. RHS, Phalaenopsis growing guide (retrieved 20 October 2026)
  2. Gardeners' World, how to care for orchids (retrieved 20 October 2026)
  3. Orchid Society of Great Britain, Phalaenopsis care (retrieved 20 October 2026)
  4. Sheffield & District Orchid Society, Phalaenopsis cultivation (retrieved 20 October 2026)
  5. Melcourt Orchid Bark Medium (retrieved 20 October 2026)
  6. RHS, peat-free composts and mulches (retrieved 20 October 2026)
  7. GOV.UK, horticultural peat sale announcement (retrieved 20 October 2026)
  8. amazon.co.uk listings captured for this comparison (retrieved 20 October 2026)