Dotted loosestrife

Dotted loosestrife: how do you recognise it?

Habit

Upright, dense clump 60–80 cm tall and about 60 cm wide, spreading by rhizomes.

Leaves

Lance-shaped to oval, 5–10 cm long, softly hairy, in whorls of three or four around the stem.

Flower

Star-shaped flowers 2–3 cm across, in whorls in the leaf axils along the upper part of the stem, from June to August.

Colour

Bright yellow. In ‘Alexander’ and ‘Golden Alexander’ the variegated foliage is an asset too.

Roots

Creeping rhizomes just below the surface: it spreads quickly, especially in moist soil.

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

Why grow it?

• Three months of bright yellow, from June into August.
• Grows where many perennials struggle: heavy clay, wet soil and partial shade.
• Fully hardy and rarely ill: an ideal plant for beginners.
• The flowers offer oil and pollen rather than nectar, attracting special wild bees such as the yellow loosestrife bee.
• Quickly forms a dense clump that smothers weeds: handy for filling a damp corner or a pond edge.

Dotted loosestrife: where does it grow best?

• Sun to partial shade. In full sun the soil must stay moist; in deep shade it flowers less.
• Loam, clay or peaty soil, acid to chalky: it is not fussy at all.
• Normal to wet soil: it is at home beside a pond or in a damp border.
• Plant 40–50 cm apart, four to five plants per m², and allow for its urge to spread.

Light

Sun and partial shade

Soil type

Loam, clay or peat

Acidity

Not fussy

Moisture

Normal or wet

Size

0.8 m tall, 0.6 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Purple loosestrife: Purple spikes beside the yellow whorls, in the same moist soil.
• Siberian iris: Narrow, upright leaves and blue flowers for a damp border.
• Cranesbill: Blue or purple flowers that stand out well against the yellow.
• Hosta: Large leaves as a calm counterpoint in partial shade.
• Lady’s mantle: Soft, rounded leaves as a low edging at the front of the border.

Dotted loosestrife: when and how to plant it?

Plant in March–May and September–October.

1. Plant from March to May or in September–October, when the soil is not frozen or waterlogged.
2. Dig a hole twice as wide as the pot and loosen the soil at the bottom.
3. To keep it in check, set a root barrier about 30 cm deep around the hole, or plant it in a large bottomless pot.
4. Set the plant at the same depth as it was in the pot, backfill and firm well.
5. Water in thoroughly and keep the soil moist for the first few weeks.
6. Spread a layer of compost or leaf mould around the plant to keep the soil cool and moist.

Care

Water

Water generously in dry summers, especially in sun: in drought the leaves droop and their edges turn brown.

Feeding

A spadeful of compost in spring is enough. Extra fertiliser only makes it more vigorous.

Edging

Every spring, slice off the runners around the clump with a sharp spade and remove them.

Support

In sun it usually stands firm. In rich soil or shade the stems may flop: a few canes or a plant ring will help.

Deadheading

Not needed: it self-seeds little and the stems can stay until autumn.

Rejuvenating

Every three to four years, lift, divide and replant only the young outer pieces. It will flower freely again.

Tip: Plant it with a root barrier or in a large pot and edge it every spring: you enjoy the sea of flowers without it taking over the whole border.

Dotted loosestrife: when to prune it?

Pruning months: March and October.

When: Cut the dead stems down in October or in March, before the new shoots appear.

How:

• Cut all stems back to just above the ground.
• If you wait until March, cut carefully around any young shoots already coming through.
• Combine it with edging the clump in March, so everything is done in one go.

Caution: Pruning does not keep it small: it spreads underground. Edging with a spade or a root barrier does work.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In March–April or September–October, lift a clump and split it with a spade into pieces with a few buds each. Replant straight away and water.

Rhizomes

Loose pieces of rhizome with a shoot, found while edging, root easily in a pot of compost-rich soil.

Dotted loosestrife: how does it get through the winter?

Hardy to −30 °C.

• Fully hardy, to about −30 °C: no protection is needed in Belgium.
• The stems die back in autumn; in spring it regrows from the rhizomes.
• In a pot: stand it in a sheltered spot against a wall and do not let the compost dry out completely.

Diseases and pests

• Spreading: It pops up all over the border. Edge it every spring or install a root barrier.
• Slugs: They eat the young shoots in April–May. Pick them off in the evening or put a ring of coarse sand around the clump.
• Drooping or brown leaves: A sign of drought, especially in full sun. Water thoroughly and mulch.
• Flopping stems: Too much shade or too rich a soil. Move it to a sunnier spot or give some support.
• Aphids: Sometimes on the tips of young shoots. Ladybirds usually deal with them; otherwise hose them off with water.

Through the year

• March: Cut down old stems. Edge the clump. Add compost.
• April: Plant or divide. Watch out for slugs.
• May: Plant. Add support if needed.
• June: Flowering begins.
• July: Full bloom. Water in dry spells.
• August: Flowering tails off. Water in dry spells.
• September: Plant or divide.
• October: Cut down dead stems. Plant.
• November: Rest. The plant is below ground.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• Loosestrifes offer an oily substance rather than nectar. The yellow loosestrife bee collects this oil and mixes it with pollen to feed its larvae.
• The name punctata means ‘dotted’ and refers to the tiny glandular dots on the plant.
• The genus name Lysimachia refers to Lysimachus, a general of Alexander the Great. The English ‘loosestrife’, ‘end of strife’, is a translation of that Greek name.