UK compost
What compost for large bitter-cress in the UK?
Cardamine amara
More about large bitter-cress in the UK
Which compost large bitter-cress needs
For large bitter-cress the mix to buy is peat-free multipurpose compost. Thrives in nutrient-rich, water-retentive substrates alongside streams; also grows in standard moist loam enriched with leaf mould or well-rotted compost.In British garden centres the bagged growing medium is sold simply as “compost” (multipurpose, ericaceous, or loam-based John Innes), which is a different thing from the rotted garden “compost” you make in a heap — for a pot you want the bagged kind.
Peat-free compost
Buy peat-free. The sale of peat compost to home gardeners is being phased out across the UK, and the RHS recommends peat-free on environmental grounds. A good peat-free multipurpose grows large bitter-cress perfectly well; the one habit to change is watering — peat-free dries faster at the surface while still moist below, so check by feel a knuckle deep rather than trusting the look of the top.
Ericaceous or multipurpose?
Large Bitter-cress is straightforward: an ordinary peat-free multipurpose compost is right. For a big specimen or a pot it will live in for years, mixing in some loam-based John Innes No.2 or No.3 adds weight and holds nutrients longer. Ericaceous compost is not needed unless a plant is specifically a lime-hater.
For the full recipe, pH and drainage detail (US wording), see the large bitter-cress soil & potting-mix guide.
Compost for Large Bitter-cress in the UK — frequently asked questions
What compost should I use for large bitter-cress in the UK?
Use peat-free multipurpose compost. Thrives in nutrient-rich, water-retentive substrates alongside streams; also grows in standard moist loam enriched with leaf mould or well-rotted compost. In UK garden centres this is sold simply as "compost" — the bagged growing medium, not garden-made leaf-mould — so match the description above rather than a brand.
Can I use ordinary multipurpose compost for large bitter-cress?
Yes. A good peat-free multipurpose compost is exactly right for large bitter-cress. For a large or long-term pot you can mix in some John Innes No.2 or No.3 (loam-based) for extra weight and staying power.
Should the compost be peat-free?
Yes. Sales of peat compost to home gardeners are being phased out in the UK, and the RHS recommends peat-free for environmental reasons. Modern peat-free multipurpose composts grow large bitter-cress perfectly well — they dry a little faster at the surface, so check moisture by feel rather than by the look of the top.
Does large bitter-cress need grit or perlite added?
Not essential, but a couple of handfuls of perlite in the mix improves aeration and guards against overwatering — useful on a cool, damp British windowsill where compost stays wet longer.
What pot and drainage does large bitter-cress need?
Always a pot with drainage holes. Wet, humus-rich loam or marginal mud. Stand it on a saucer, empty any water that collects after watering, and never leave the pot sitting in a full outer cover — waterlogged compost in a cool UK room is the commonest cause of root rot.
More large bitter-cress care
See the full large bitter-cress care guide, its UK watering and UK hardiness.