Prostrate speedwell

Prostrate speedwell: how do you recognise it?

Habit

Low, creeping carpet 10–20 cm tall and 40 cm wide, spreading slowly.

Leaves

Narrowly oval to lance-shaped, 1–3 cm, toothed, usually grey-green to dark green.

Flowers

Small flowers in short, upright spikes 5–10 cm long, in May–June.

Colour

Deep blue; pale blue in some cultivars.

Roots

Creeping stems that root as they go and slowly widen the mat.

Flowering: May–June · Plants: March–April and September–October · Pruning: March and July

Why grow it?

• A thick carpet full of deep blue flowers in May and June.
• Drought-tolerant and suited to poor, dry, sunny soil.
• An ideal ground cover for a rock garden, wall top, gravel garden or path.
• Bees and other insects visit the flowers.
• Low maintenance and fully hardy.

Prostrate speedwell: where does it grow best?

• Full sun: the sunnier the spot, the richer the flowering.
• Well-drained, lean soil: sand or loam, neutral to chalky.
• Dry to normal soil; it dislikes wet feet, especially in winter.
• Allow 30–40 cm per plant; in a rock garden you can plant it closer.

Light

Sun

Soil type

Sand or loam

Acidity

Neutral or chalky

Moisture

Dry

Size

0.15 m tall, 0.4 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Stonecrop: Fleshy leaves and late flowers in the same dry sun.
• Yarrow: Low species with flat heads in yellow or white.
• Thyme: Creeping herbs that tolerate the same dry, sunny spot.
• Sheep’s fescue: Fine blue-grey tufts as a calm backdrop.

Prostrate speedwell: when and how to plant it?

Plant in March–April and September–October.

1. Plant in March–April or in September–October, when the soil is neither frozen nor waterlogged.
2. Dig a hole as wide as the root ball; on heavy clay, mix coarse sand or grit into the soil.
3. Set the plant at the same depth as in its pot and firm the soil well.
4. Space plants 30–40 cm apart, or 20–25 cm for a quickly closing mat.
5. Water in straight away; in the first year water again in dry weather.

Care

Water

Rarely needed once established; water only during long dry spells in the first year.

Feeding

Not needed: on poor soil it stays compact and flowers freely.

Mulching

A thin layer of grit or fine stone chippings keeps the plant dry and weeds down.

Spent flowers

Trim lightly after flowering; this keeps the mat compact and gives fresh foliage.

Dividing

Divide the mat every 3–4 years when the centre goes bare.

Tip: Trim lightly after flowering so the mat stays compact and grows fresh foliage. Plant it in full sun on well-drained soil, in gravel, between stones or on top of a low wall.

Prostrate speedwell: when to prune it?

Pruning months: March and July.

When: After flowering in July, with a light tidy-up in March.

How:

• After flowering, lightly trim back the faded spikes and the longest runners.
• In March, remove brown or damaged leaves from the winter.
• Trim back shoots that have strayed too far if the mat gets too large.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In spring or in September: cut the mat with a spade into pieces with roots, and replant straight away.

Cuttings

After flowering, in June–July, take cuttings of 5 cm from non-flowering shoots in moist cutting compost; they root within a few weeks.

Prostrate speedwell: how does it get through the winter?

Hardy to −30 °C.

• Fully hardy, to about −30 °C: no protection is needed in Flanders.
• Wet winters on heavy clay are the main risk: provide good drainage and it will survive easily.
• In a pot: use soil with plenty of coarse sand and do not stand the pot in a wet corner.

Diseases and pests

• Root rot: Limp, brown patches in the mat in wet soil, especially in winter. Plant in a dry spot or improve the drainage.
• Powdery mildew: White powder on the leaves in damp, muggy weather. Allow space and remove affected leaves.
• Slugs: Nibbled shoots in spring. Collect them in the evening and scatter coarse sand or grit around the plant.
• Bare patches: The centre opens up after a few years. Divide the mat in spring and replant the young pieces.

Through the year

• March: Tidy dead foliage. Plant. Divide.
• April: Plant. Apply mulch.
• May: Flowering begins.
• June: Full flower. Take cuttings.
• July: Trim lightly after flowering. Take cuttings.
• August: Water during long dry spells.
• September: Plant or divide.
• October: Plant.
• November: Rest.
• December: Rest.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• The species name prostrata means ‘stretched out’ or ‘lying flat’ and refers to the creeping habit.
• In the wild it grows on dry, sunny grassland and rocky slopes.
• Thanks to its low, creeping growth it is popular in rock gardens and on wall tops.