Brooklime

Brooklime: how do you recognise it?

Habit

Low, creeping to ascending plant 20–30 cm tall, whose rooting stems form a mat about 50 cm across.

Leaves

Opposite, round to oval, 2–6 cm, fleshy, glossy and hairless, with a finely toothed edge.

Stem

Round, fleshy and hollow; roots at the nodes wherever it touches wet ground.

Flower

Bright blue flowers about 7 mm across with a white centre, in sprays from the leaf axils, from May to September.

Pond zone

Wet bank and marsh zone, down to about 10 cm below the water surface.

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

Why grow it?

• Quickly hides the pond edge and liner under a low, green mat.
• Long flowering: small blue flowers from May to September.
• Bees, hoverflies and other small insects visit the flowers.
• Its creeping stems in shallow water give cover to tadpoles and small pond creatures, and frogs use them to climb in and out of the water.
• Native, fully hardy and very easy to propagate.

Brooklime: where does it grow best?

• Sun or partial shade; it flowers best in sun, as long as the soil stays wet.
• Wet, fertile loam, clay or peaty soil, neutral to chalky; also in the mud beside a stream.
• Water depth: from a wet bank to 5–10 cm of water above the soil.
• It tolerates running water, so it also suits a small stream or waterfall.
• Allow about 4 plants per square metre for a mat that closes quickly.

Light

Sun and partial shade

Soil type

Loam, clay or peat

Acidity

Neutral or chalky

Moisture

Wet

Size

0.3 m tall, 0.5 m wide

Hardiness

Hardy (to -25 °C)

Goes well with

• Water forget-me-not: Even more small blue flowers in the same wet margin, from May into summer.
• Marsh marigold: Large, glossy yellow flowers in early spring, before the brooklime starts flowering.
• Water mint: Scented leaves and lilac flowers in the same shallow zone.
• Yellow flag iris: Tall, upright sword-shaped leaves behind the low mat of brooklime.
• Purple loosestrife: Tall purple spikes on the bank; together a feast for bees.

Brooklime: when and how to plant it?

Plant in April–June and September.

1. Plant from April to June or in September.
2. Use an aquatic basket filled with heavy garden soil or clay, or plant straight into the mud of the bank; no potting compost or fertiliser.
3. Set the root ball just below the soil surface and top the basket with 2–3 cm of gravel, so the soil does not wash out.
4. Place the basket 0–10 cm below the water surface, with about 50 cm between plants.
5. Water plants on the bank in well and keep the soil wet until they have established.

Care

Water

On the bank the soil must always stay wet; in dry summers, top up the pond with rainwater.

Feeding

Not needed: in a pond, extra nutrients mainly feed algae.

Keeping in check

In summer, pull out or cut stems that spread too far or grow over other plants.

Renewing

After a few years the stems become long and bare; replace the plant with young cuttings.

Tidying

In March, remove the dead stems so they do not rot in the water.

Tip: Plant it where the bank meets the water: it hides the pond edge, and frogs can easily climb in and out.

Brooklime: when to prune it?

Pruning months: March and July.

When: Cut back in July when the plant becomes long and untidy, and clear the dead stems in March.

How:

• In July, cut the stems back by half: it soon regrows and keeps flowering into September.
• Remove stems that grow over other plants, roots and all.
• In March, clear dead and brown stems with scissors or a pond rake.
• Leave what you take out of the water on the bank for a day, so pond creatures can crawl back.

Caution: Every piece of stem can root: do not let cut pieces float in the pond if you want to keep it in check.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Cuttings

From May to August, put pieces of stem about 10 cm long with a few nodes into wet soil or a glass of water. They root within a week or two.

Division

In April or September, cut a rooted piece from the mat and replant it elsewhere.

Self-seeding

On wet, open ground it sometimes seeds itself; move the seedlings in spring.

Brooklime: how does it get through the winter?

Hardy to −25 °C.

• Fully hardy, to about −25 °C: no protection needed.
• In mild winters some stems stay green; in hard frost the top growth dies back and the plant regrows in spring.
• Leave the stems in place over winter: they protect the plant and shelter small creatures.
• During long frosts, keep a hole open in the ice of a pond with fish, without hitting the ice.

Diseases and pests

• Long, bare stems: After the first flush or after a few years the plant becomes untidy. Cut back in July and replace with young cuttings every few years.
• Spreading too far: It grows over other marginal plants. Pull out stems and keep the plant in a basket.
• Slugs and snails: They eat small holes in the leaves. Usually harmless: the plant soon regrows.
• Aphids: Small black aphids on the shoot tips in summer. Hose them off; do not use pesticides near the pond.
• Drying out: On a bank that dries out it soon wilts. Choose a spot that stays wet and top up the pond in time.

Through the year

• March: Clear the dead stems.
• April: Plant or divide. New shoots appear.
• May: First small blue flowers. Still time to plant. Take cuttings.
• June: Flowering. Shorten stems that spread too far.
• July: Cut back by half if it becomes untidy.
• August: Second flush. Top up the pond with rainwater in dry spells.
• September: Last flowers. Plant or divide.
• November: Resting. Leave the stems as protection.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• Speedwells such as brooklime used to be placed in the figwort family; since DNA studies they belong to the plantain family.
• In the wild, brooklime often grows by springs and clear streams, together with watercress.
• A broken piece of stem that lands in the mud soon becomes a new plant: that is how brooklime spreads downstream along brooks.