Question: Can I grow orchids in pieces of wine cork?
Victoriaville, Quebec, Canada
Answer: Absolutely. In fact, orchid-lovers use cork in all its forms as a substrate for their plants.
Most often orchids are mounted on slabs of orchid bark, allowing them to grow much as they would in the wild (most orchids are epiphytes and grow on tree branches). However, chipped cork bark is an ingredient in many orchid potting mixes and can also be used alone as an orchid substrate. You’ll even find chipped cork sold commercially for that purpose on orchid supplier web sites.
Of course, none of the products above are made from old wine corks, but rather directly from cork bark as harvested from trees, but there is nothing that is toxic to orchids in corks harvested from wine bottles and no reason you can’t use them. Many home orchid growers do.
Making a Wine Cork Orchid Substrate
Break wine corks into pieces a quarter inch (5 mm) in size or larger. Discard any dust or finer pieces: they could reduce air circulation to the roots. You can use your “cork chips” alone or mix them with other products traditionally used as components of orchid substrates, such as osmunda, rock wool, sphagnum, conifer bark or lava rock.
To learn how to repot an orchid, read How to Repot an Orchid.
Orchids in Whole Corks
Some orchid hobbyists use intact wine corks as a substrate, especially for orchids that require a great deal of aeration around their roots, like vandas (Vanda). Why not?
Red or White?
There remains one question for which I could not find an answer: do the orchids prefer white wine corks or red wine corks?
Carry out your own tests and see! (I suspect drinking your way to the conclusion could be just as enjoyable as carrying out the test!)