Marsh helleborines (Epipactis palustris) are perennial plants and are fully hardy in the UK, though plants in pots may be vulnerable to low winter temperatures. They are suitable for neutral or alkaline damp soil conditions.
It has a beautiful showy flower, dark pink with a white frilly lip. They grow in a variety of wet marshy habitats, always alkaline or neutral soils. They are found in meadows fens and dune slacks where the conditions are right for them. The leaves appear in spring and flowering is June to August. Seed setting is in September. The whole plant dies back in autumn and is dormant through the winter. It spreads easily by rhizome and a single plant will form a small clump in 3-5 years. Plant out at the beginning or end of the dormancy period i.e. early autumn or early spring. Place a dormant plant with the tip 2cm below the surface, or if the plant has green aerial parts, keep the soil level the same as the compost in the pot .They prefer full sun but if planted in pots beware of them overheating or drying out by standing the pot in shallow water. If planted into a grassland it should be under a management regime for a wildflower meadow. In grassland it requires a very sparse sward and ground that is damp all year round.
For pots use a well drained growing mix of 1 part peat free compost, 1 part perlite, 1 part grit, 2 parts sieved calcareous topsoil and a handful of garden lime. Even though this is a plant of wet habitats, do not let pots stand in water during freezing conditions.