Lousewort

How to recognise it

Growth form

Low, short-lived perennial or biennial of 5–20 cm, with an upright central stem and several sprawling to ascending side stems from the base.

Leaf

Small, deeply pinnate, with crinkly, toothed lobes, often tinged red.

Flower

Pink lipped flowers of about 2 cm in a loose spike. The upper lip is helmet-shaped with two small teeth at the tip; the lower lip has three lobes. Flowers from May to July.

Calyx and fruit

Inflated, hairless calyx with five unequal, toothed lobes. Inside it ripens an oblique, oval capsule with a few fairly large seeds.

Roots

Slender roots with small suckers (haustoria) that attach to the roots of neighbouring plants.

Confusion with

Marsh lousewort (Pedicularis palustris) is larger, up to 60 cm, with a single upright, branched stem, a hairy two-lipped calyx and an upper lip with four teeth. It grows in marshy meadows and is even rarer.

Flowering: May–July · Pruning: September

Why grow it?

• A characteristic species of wet, nutrient-poor heath and heathy grassland: where it grows, nature is still in good condition.
• The pink flowers are visited and pollinated mainly by bumblebees, which find nectar early in the season.
• A fascinating hemiparasite that draws on the roots of grasses and sedges and so holds the grasses back a little, giving room to other flowers.
• In May–June it colours wet heath and peaty paths pink, together with cross-leaved heath and tormentil.
• A rare species that shows how important rewetting, mowing and turf-stripping are in heathland management.

Lousewort: where does it grow best?

• In the wild on damp to wet heath, in heathy grassland, on peaty or sandy paths and at the edges of heathland pools.
• Sun to light shade, in low, open vegetation.
• Wet to damp, nutrient-poor, acid soil: peaty sand or peat, never fertilised or limed.
• In a garden it is only feasible in a wet, acid, poor spot with low grasses and sedges, for example a wet heather garden.

Goes well with

• Cross-leaved heath: Pink bells on the same wet, acid heath.
• Tormentil: Small yellow flowers with four petals, on the same poor soil.
• Common cottongrass: White tufts in wet, peaty spots.
• Devil’s-bit scabious: Violet-blue pompoms in late summer, when the lousewort has finished flowering.
• Heath-grass: A low grass of heathy grassland, and a possible host plant.

Lousewort: when and how to plant it?

1. Lousewort is not an ordinary garden plant: as a hemiparasite it needs host plants, and it only grows on wet, nutrient-poor, acid soil.
2. If you have such a wet heathy or peaty spot, sow fresh seed of local origin in September–October, from a nursery or seed supplier specialising in native plants.
3. Sow directly among low grasses and sedges such as heath-grass and common sedge: the seedlings must find a host plant quickly.
4. Press the seed onto bare, damp peat or sand and do not cover it. Winter cold helps the seed germinate in spring.
5. Keep the soil wet all year round, preferably with rainwater, and never feed.
6. Never pick it or dig it up in the wild: it is rare, and plants that are dug up die because they lose their host plants.

Care

Water

The soil must stay damp to wet all year. Use rainwater: limy tap water makes the soil less acid.

Feeding

Never: fertiliser and lime destroy its habitat.

Mowing

Mow the wet heath or poor grassland once a year in September and remove the cuttings, so that the vegetation stays low and open.

Bare patches

Small bare, damp patches help the seed germinate. In nature reserves these are created by small-scale turf-stripping.

Tree seedlings

Pull out young birch, pine and willow in good time, or the spot will close over.

Tip: If you really want to help it, support the nature group that manages the wet heath near you: a well-managed wet heath does more for lousewort than any garden.

Pruning and mowing

Pruning months: September.

When: No pruning is needed. Only mow the vegetation it grows in from September, once the seed has dropped.

How:

• Mow short and remove the cuttings so that the soil stays poor.
• Leave part uncut if you want to be sure that enough seed falls.
• Remove young trees and shrubs, which would otherwise soon close over the spot.

Caution: Do not mow in May–July: you would cut off the flowers and the seed.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Only from seed, sown where it is to grow in September–October among host plants. The seed must overwinter outdoors and germinates in spring.

Division or transplanting

Not possible: the plant’s roots are attached to those of its hosts, and it rarely survives being moved.

Lousewort: how does it get through the winter?

Hardy to −25 °C.

• After setting seed the top growth dies back; the plant overwinters as a short rootstock or as seed in the soil.
• Fully hardy, even in harsh winters on the wet heath.
• Wet, open ground in winter and spring is important: that is when the seed can germinate.

Diseases and pests

• Drying out: When the water table drops, it disappears. Keep the spot wet; in the garden with collected rainwater.
• Nitrogen enrichment: Nitrogen from the air and from fertiliser lets grasses such as purple moor-grass take over. Mowing and removing the cuttings helps, in reserves also turf-stripping.
• Scrub invasion: Young birch and pine crowd it out. Pull up tree seedlings before they grow big.
• Failed transplanting: The plant loses its host plants. Sow instead of transplanting.

Through the year

• April: Seedlings and new shoots appear.
• May: Flowering begins. Do not mow.
• June: Full flower, with bumblebees visiting.
• July: Last flowers and seed setting.
• August: The seed capsules ripen.
• September: Mow and remove the cuttings. Sow fresh seed among host plants.
• October: Still time to sow. Remove tree seedlings.
• November: Collect rainwater; the soil should go into winter wet.

Did you know?

• Pedicularis comes from the Latin pediculus, ‘louse’: farmers used to believe that sheep grazing pastures with lousewort caught lice, which is also where the English name comes from.
• It is a hemiparasite: its green leaves make sugars, but with small suckers on its roots it taps water and nutrients from the roots of nearby plants.
• It used to be placed in the figwort family; DNA studies moved it, along with other hemiparasites such as the yellow-rattles, to the broomrape family.