Bog rosemary

Bog rosemary: how do you recognise it?

Habit

Low, creeping dwarf shrub 20–30 cm tall and about 50 cm across, with thin, upright shoots.

Leaves

Narrow, linear and leathery, with rolled-under edges; blue-green above, whitish below; evergreen.

Flower

Small, rounded, nodding bells in clusters at the shoot tips, in May–June.

Colour

Pale pink to white, on deeper pink stalks.

Roots

Fine, shallow roots and creeping rhizomes; like most heathers it lives in partnership with soil fungi.

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

Why grow it?

• A native plant for a bog garden, heather garden or the wet edge of a pond.
• Blue-green leaves all year round, even in winter.
• Dainty pink bells in May–June.
• Stays low and small: suits a small garden or a large container.
• Grows where few other shrubs survive: acid, wet and poor ground.

Bog rosemary: where does it grow best?

• Sun to light partial shade; in shade the plant becomes sparse.
• Acid, peaty or humus-rich sandy soil, very acid (pH around 4–5) and never chalky.
• Wet to very moist: at a pond edge, in a bog bed or in a heather garden with a high water table.
• Water only with rainwater; tap water often contains lime.
• Plant 30–40 cm apart, in small groups.

Light

Sun and partial shade

Soil type

Sand or peat

Acidity

Acid

Moisture

Wet

Size

0.3 m tall, 0.5 m wide

Hardiness

Hardy (to -35 °C)

Goes well with

• Cross-leaved heath: Pink bells for the same wet, acid soil.
• Cranberry: A creeping ground cover with red berries for a bog bed.
• Cotton grass: White tufts in spring, in the same wet, acid soil.
• Heather: For the slightly drier edge of a heather garden.

Bog rosemary: when and how to plant it?

Plant in March–April and September–October.

1. Plant in March–April or September–October.
2. Prepare a planting area with ericaceous compost or heather soil mixed with some sand; on chalky soil this only works in a lined bog bed or container.
3. Set the plant at the same depth as in the pot and firm gently.
4. Leave 30–40 cm between plants.
5. Water in with rainwater and keep the soil constantly moist.
6. Mulch with pine needles or fine pine bark to keep the soil acid and moist.

Care

Watering

Never let the soil dry out; in dry spells water generously with rainwater.

Feeding

Usually not needed. At most a small dose of ericaceous fertiliser in spring.

Mulching

Each spring, a thin layer of pine needles or pine bark.

Weeding

Remove grasses and tree seedlings, which quickly smother this low plant.

In a container

Use a tub with few or no drainage holes, filled with acid compost, and keep it wet.

Tip: Make a bog bed: dig a hole about 40 cm deep, line it with pond liner pierced with a few holes, fill it with acid compost and keep it wet with rainwater. That way you can grow bog rosemary even in a garden with chalky soil.

Bog rosemary: when to prune it?

Pruning months: June–July.

When: Hardly needed. To keep the plant compact, trim lightly after flowering, in June–July.

How:

• Lightly trim spent flower clusters and overlong shoots.
• Remove dead or brown shoots in spring.
• Never cut hard into old wood.

Caution: Wear gloves and clear up the clippings: all parts are poisonous.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Runners

In spring, detach rooted runners at the edge of the mat and pot them up in acid compost.

Semi-ripe cuttings

In July–August, root 3–5 cm cuttings in a mix of acid compost and sand, under plastic.

Division

In spring, carefully split a rooted mat into pieces and replant straight away.

Bog rosemary: how does it get through the winter?

Hardy to −35 °C.

• Very hardy, to −35 °C: no protection is needed in Belgium.
• Evergreen: the blue-green leaves stay attractive all winter.
• In a container: make sure the soil does not dry out in sunny, frosty weather and water on frost-free days.

Diseases and pests

• Yellow leaves: Chlorosis from lime or tap water. Water with rainwater and add acid compost or pine needles.
• Brown, dried-out shoots: A sign of drought. Keep the soil constantly wet, especially in summer.
• Overgrown by weeds: Grasses and stronger plants crowd out this low plant. Weed regularly.
• Dwindling in the border: It does not last long in ordinary garden soil. Plant it in a bog bed or a container of acid compost.

Through the year

• January: Rest. Blue-green winter leaves.
• March: Planting. Remove dead shoots.
• April: Planting. Mulch with pine needles.
• May: Flowering begins.
• June: Flowering. Trim lightly after flowering.
• July: Water generously with rainwater in dry spells. Light trim.
• August: Watering. Take semi-ripe cuttings.
• September: Planting.
• October: Planting.
• December: Rest. Water containers on frost-free days.

Edible and useful

Not edible. Bog rosemary is poisonous in all its parts: like rhododendron it contains grayanotoxins, which cause vomiting, dizziness, a slow heartbeat and low blood pressure. Despite its name and its narrow grey-green leaves with rolled edges, it is not rosemary: never use the leaves as a herb or for tea. Especially dangerous to sheep and goats that nibble it. Wear gloves when pruning and clear up the clippings. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Did you know?

• Linnaeus named the plant during his journey through Lapland in 1732: the little plant on a hummock in the bog reminded him of Andromeda from Greek myth, chained to a rock in the sea.
• Despite the name bog rosemary, it is not related to rosemary but belongs to the heather family.
• In the wild it often grows with sphagnum moss, which keeps the ground acid and wet.