UK compost
What compost for spider orchid (brassia) in the UK?
Brassia spp.
More about spider orchid (brassia) in the UK
Which compost spider orchid (brassia) needs
For spider orchid (brassia) the mix to buy is peat-free multipurpose compost cut roughly half-and-half with horticultural grit or perlite. Use a coarse, open epiphyte mix based on medium-grade fir bark, optionally with perlite, charcoal or coconut husk for aeration; never standard potting soil. Pot in a container with generous drainage. Repot every 2-3 years in spring with fresh bark as the mix breaks down, but never repot while in bloom.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 spider orchid (brassia) 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?
Spider Orchid (Brassia) does not want a rich, water-holding compost — it wants sharp drainage. Cut peat-free multipurpose roughly half-and-half with horticultural grit, sharp sand or perlite, and always pot into a container with drainage holes. A "cactus and succulent" bagged mix is a ready-made shortcut.
For the full recipe, pH and drainage detail (US wording), see the spider orchid (brassia) soil & potting-mix guide.
Compost for Spider Orchid (Brassia) in the UK — frequently asked questions
What compost should I use for spider orchid (brassia) in the UK?
Use peat-free multipurpose compost cut roughly half-and-half with horticultural grit or perlite. Use a coarse, open epiphyte mix based on medium-grade fir bark, optionally with perlite, charcoal or coconut husk for aeration; never standard potting soil. Pot in a container with generous drainage. Repot every 2-3 years in spring with fresh bark as the mix breaks down, but never repot while in bloom. 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 spider orchid (brassia)?
Not on its own — multipurpose compost holds too much water for spider orchid (brassia) and will rot the roots. Cut it roughly 50:50 with horticultural grit, sharp sand or perlite so it drains fast.
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 spider orchid (brassia) perfectly well — they dry a little faster at the surface, so check moisture by feel rather than by the look of the top.
Does spider orchid (brassia) need grit or perlite added?
Yes — spider orchid (brassia) must have sharp drainage. Add about one part horticultural grit or perlite to one part compost, and always use a pot with drainage holes.
What pot and drainage does spider orchid (brassia) need?
Always a pot with drainage holes. Free-draining medium-grade orchid bark mix. 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 spider orchid (brassia) care
See the full spider orchid (brassia) care guide, its UK watering and UK hardiness.