This genus of hardy terrestrial orchids whose name derives from the Greek for testicle because of the two oval tuberoids found in the spring. They are a group of 21 summer dormant species found in many parts of the northern hemisphere. All flower from base upwards with the exception of orchis italica. They produce a rosette of leaves in the autumn, along with roots that appear at the top of the tuber and drop downwards seeking water. Some rosettes opening fully before Christmas whilst others only open when the temperature warms up in March.
Flowering takes place from April to July depending on the species. Their individual requirements are variable but most require alkaline conditions. As with all summer dormant species they are adapted to being dry during that period.
There are a number that grow in the UK naturally whilst others can only be grown in an alpine house because of the level of rainfall. When grown in pots it important not to let the compost dry out during the growing period but also to ensure that the rosette is not water logged as this can cause neck rot. Many growers use clay pots sunk into damp sand and only water the sand.
As the late spring arrives the single growing point will start to develop the single flower spike on a stem between 25 and 50 cm tall depending on the species. At the same time the "dropper" starts to grow to produce the new tuber for next season. In order to maximise the size of the new tuber many growers will remove the flower spike as it begins to go over and then no seed pods are produced.
Pots should be allowed to dry out during the summer so the new tuber matures in the same way as a potato. If the tuber remains damp and it gets hot in mid summer the tuber may rot. Conversely the compost should not be allowed to fully dry out as the tuber will becoome desiccated.
The above gives good instructions to the buyers of these plants which are sent out potted to UK customers. It is not possible to plant out some species after the rosette is formed as the roots are too fragile and most of the soil fal of them when removed from the pot. To overcome this you could plunge the pot into the soil for the season and then plant out the following summer.
Note, that different species have different requirements as some are not easy to grow in the UK. Tubers are usually sent out potted to UK customers until late autumn (depending on species) but bare rotted to other countries. It is not sensible to send if there is a full rosette, especially if the postal service is slow.