There are two basic species of Molinia that we are interested in on this page as far as ornamental grasses are concerned. They are Molinia caerulea and the subspecies M. c subsp. arundinacea. They share a common name of Purple Moor Grass. The purple aspect probably refers to the 'moors' for the plant has no purple colouring!
There are several varieties within those groups that are good for garden use. Molinia are quite dainty grasses - generally having tidy clumps of foliage with long erect stems of flowers.
The garden interest in the Molinias, is that they are attractive from mid summer right through until the middle of winter. Summer for their foliage and flower spikes.
Autumn and winter for the good autumn colour of the foliage, and the long lasting seedheads which of course replace the earlier flowerheads.
L-R Molinia caerulea subsp. arundinacea 'Windspiel' | Molinia caerulea Variegata | Same as centre but in autumn.
The flower and seed heads are held above the foliage - attractively graceful - yet sturdy enough to survive the strongest winds. Remember the origin of these grasses are open, exposed, damp moorlands. Molinia caerulea subsp. arundinacea is a British native, so should well be used to the varying climates!
All of the Molinia group are happiest in damp places, or at least in soils that do not dry out. However, if watered in drought conditions, they will also live in most normal garden soils.
As with many grasses, full sun is the best position, but Molinia is also happy in partial shade, if attention is given to watering - especially if that shade is from trees. A damp soil on the side of a wall or fence that only gets afternoon or morning sun is no problem.
As Molinia caerulea types are quite compact and non invasive - forming neat tufts - they lend themselves to spots at the front of herbaceous borders or shrub beds, and will also do well in containers on the Patio. Autumn colour is normally good - for foliage and seed head spikes.
Molinia caerulea reaches a height of around 4 feet (The flower spikes) and a spread of 2 feet. It is a good sight in the autumn with its arching foliage and nodding seedheads. The variegated forms are the smallest - with a height of flower spikes of around 20in (50cm).
Molinia caerulea and its cultivars are easy to grow from seed - but the seedling grasses can be variable, and not true to form. Seed is best sown in seed trays in coldframe or unheated glasshouse in spring, and the resultant seedlings potted individually to grow on for a year before planting out in the garden.
For a few plants only, then divide the parent plant in the spring - just as the new growth starts. Take small sections off the parent and grow for a year in pots in sheltered place - but not to shaded. These can then be planted out in the following spring. Divided plants will always come true to type - so is a much better way of propagation if you want the true Variegated forms. Molinia variegated forms rarely come true from seed and usually result in many plain green seedlings.
Other than the fact that they may suffer a little in drought conditions if not watered, Molinia have no pest or disease problems that we know of. It is one of the many reasons why growing ornamental grases is so stress free for the gardener.