Photo: Daderot, Public domain · source
Ornamental grass · Poaceae
Blue moor grass
Sesleria caerulea
In other languages: Blauwgras (Nederlands) · Seslérie bleue (Français)
Blue moor grass is a small, evergreen grass of limestone rocks, dry chalk and limestone grassland and mountain slopes in Europe. It also grows wild in Belgium, mainly on limestone rocks and dry limestone slopes in the Meuse basin. It forms dense clumps of narrow leaves that are blue-grey on one side and green on the other, so the clump looks blue-green and slightly silvery. As one of the first grasses to flower, it blooms from March, with short, egg-shaped, blue-purple spikes hung with pale anthers. Gardeners use it in rock gardens, on dry banks, on walls and as a low, evergreen edging.
Light
Sun or partial shade
preferably some sun
Moisture
Dry to normal
no wet feet
Legal basis
Sand, loam or clay
neutral to chalky
Hardiness
Fully hardy
down to -30 °C
Size
0.3 m
tall, 0.3 m wide
Flowering
March–May
| Pruning months | February and June |
|---|---|
| Height | 0.3 m |
| Native to Belgium | Yes |
| Poisonous to people and pets | Not known to be poisonous |
| Flowering | March–May |
Identify
Blue moor grass: how do you recognise it?
- Habit
- Low, dense clump of leaves about 20 cm tall, with flower stems to 30 cm.
- Leaves
- Narrow, blue-grey on one side and glossy green on the other; evergreen.
- Flowers
- Short, egg-shaped spikes of 1–3 cm in March–May, blue-purple to grey-blue, with pale anthers.
- Roots
- Deep and fibrous; it anchors itself well in rock crevices and on slopes.
- Growth
- Grows slowly and gradually spreads into a dense mat.
Flowering: March–May · Plants: March–May and September–October · Pruning: February and June
In your garden
Why grow it?
- One of the first grasses to flower: blue-purple spikes as early as March.
- Evergreen, with blue-green leaves all year round.
- Perfect for dry, chalky soil, rock gardens and walls.
- Native and valuable in a chalky wildlife garden.
- Small and neat: it also suits a small garden or a pot.
Blue moor grass: where does it grow best?
- Sun to part shade.
- Free-draining soil: sand, loam or clay, neutral to chalky. Limestone grit is ideal.
- Dry to moist but not wet; avoid wet feet in winter.
- Plant 25–30 cm apart, in small groups or as an edging.
- Light
- Sun and partial shade
- Soil type
- Sand, loam or clay
- Acidity
- Neutral or chalky
- Moisture
- Dry or normal
- Size
- 0.3 m tall, 0.3 m wide
- Hardiness
- Hardy (to -30 °C)
Goes well with
- Pasque flower: Purple bells in April, at the same time as the moor grass; also a chalk plant.
- Grape hyacinth: Small blue spring bulbs that flower at the same time.
- Wild thyme: Low, fragrant cushions for bees.
- Carthusian pink: Pink flowers in summer on dry, chalky soil.
- Rock rose: Small yellow flowers in summer on the same chalky soil.
Maintenance
Blue moor grass: when and how to plant it?
Plant in March–May and September–October.
- Plant in March–May or in September–October.
- Loosen the soil and on heavy ground mix in coarse sand or limestone grit.
- Set the plant at the same depth as in the pot.
- Plant 25–30 cm apart.
- Water well after planting and in dry spells during the first weeks.
- Mulch with gravel or grit.
Care
- Water
- Only in dry spells during the first year.
- Feeding
- Not needed; poor soil keeps it compact.
- Tidying
- In late February, comb out the dead leaves before flowering starts.
- Spent flowers
- Cut off the flower stems in June if they look untidy.
Tip: Comb out the dead leaves in late February, before the spikes appear: in March the blue-purple flowers then stand out nicely above a fresh clump.
Blue moor grass: when to prune it?
Pruning months: February and June.
When: Evergreen: do not cut it back, only tidy it in late February before flowering, and remove spent stems in June if you wish.
How:
- Comb the dead, brown leaves out of the clump with your fingers.
- Cut away last year’s old flower stems.
- In June, cut off the spent stems if you do not like them, or leave them if you want to collect seed.
Caution: Do not cut it short in March: you would remove the young flower spikes.
Propagation
- Division
- In September, or in spring after flowering: lift a clump, split it and replant straight away.
- Seed
- Sow ripe seed in summer in a pot of lean compost; plant the seedlings out in autumn or spring.
Blue moor grass: how does it get through the winter?
Hardy to −30 °C.
- Fully hardy to about −30 °C: no protection needed.
- The leaves stay mostly blue-green in winter.
- Heavy, wet soil is the biggest risk: plant it in a free-draining spot.
Diseases and pests
- Rot: The clump dies after a wet winter on heavy soil. Plant in a free-draining spot and mulch with grit.
- Brown leaves: Dead leaves in the clump after winter. Comb them out in late February.
- Bare clump: Old clumps go bare in the middle. Divide them and replant the young pieces.
- Few flowers: Too much shade or too rich a soil. Choose a sunny, lean spot.
Through the year
- February: Comb out dead leaves before flowering.
- March: Flowering begins. Plant.
- April: Flowering. Plant.
- May: Last flowers. Plant. Divide after flowering.
- June: Cut off spent stems or collect seed.
- July: Water young plants in dry spells.
- September: Plant and divide.
- October: Plant.
- December: Blue-green clumps in the winter garden.
You and this species
Did you know?
- The leaves are two-coloured: turn a leaf over and you will see blue-grey on one side and green on the other.
- In northern England, blue moor grass is characteristic of the limestone grasslands of the Yorkshire Dales.
- ‘Caerulea’ means ‘sky blue’ and refers to the colour of the flower spikes.