Purple Toothwort – Lathraea clandestina

A few weeks ago my friend Chris Lansdell asked me where he could find Moschatel in the local area and I gave him details of a couple of sites, including at Natural Surroundings at Bayfield. As a “thank you” he told me that the Purple Toothwort was in flower at Bowthorpe, on the western outskirts of Norwich. I was originally told about the plants a couple of years ago, but didn’t make the trip to see them. This time, I decided I would go and I’m glad I made the effort (just a fifteen minute cycle ride from home). The plants were growing on a bank in a shady spot underneath some Willow trees.

Purple Toothwort, Lathraea clandestina is a low growing, perennial plant that is parasitic on the roots of various trees, especially Poplar (Populus) and Willow (Salix). Other plants may be used too, including  Acer (Sycamore / Maples), Alder (Alnus), Box (Buxus), Hornbeam (Carpinus), Hazel (Corylus), Walnut (Juglans), Metasequoia, Rhododendron, Yew (Taxus) and Gunnera. The plant can be found in the damp shady places where its hosts grow.

Purple Toothwort is a member of the family Orobanchaceae, along with Broomrapes (such as Purple Broomrape and Ivy Broomrape), Eyebrights, Yellow Rattle and Red Bartsia. Like the Broomrapes, Purple Toothwort has no chlorophyll and relies on food taken from its host. It bears small, simple scale leaves on alternate sides of its stem and its very pretty purple flowers shoot upwards from the stems, appearing from March to May. These develop into explosive seed capsules later in the summer.

The plant is hardy but early flowers may sometimes be damaged by frost. It is a fairly recent introduction to the British Isles (a neophyte). It was brought into Britain as an attractive garden curiosity and was planted at Kew Gardens in 1888. It was first reported from the wild in 1908 at Coe Fen in Cambridgeshire, where it was probably deliberately planted. It can still be found there. Purple Toothwort is found in various parts of England and Wales, with a few outlying colonies in Scotland and Ireland. Its native home is across the English Channel in Belgium, France, Spain and Italy.

Purple Toothwort flowers are pollinated by bumblebees. I saw a single Tree Bumblebee (Bombus hypnorum) worker when I made my visit, but it was flying just above the flowers, rather than venturing inside. The flowers have very alkaline nectar, which tastes of ammonia, though I only found this out after my visit. The taste or alkalinity is thought to deter birds and ants from robbing the nectar from the flowers without pollinating them.

There are several other species of Lathraea in Europe, all parasitic and lacking chlorophyll. In Britain we have one native species, Toothwort, Lathraea squamaria. It usually uses Hazel (Corylus) as a host, but can sometimes be found on Elm (Ulmus), Ash (Fraxinus), Alder (Alnus), Walnut (Juglans) and Beech (Fagus). One grows at Kew Gardens, under a Black Walnut tree. Further afield Toothwort grows as an annual or perennial in lowland deciduous woodland, in hedgerows, and on the banks of rivers and streams. It has white or creamy to pinkish-purple flowers, produced from March to May. I have yet to see it, as it is more or less absent from East Anglia.

The generic name Lathraea comes from the Greek word lathraios, meaning hidden. Clandestina means secret (clandestine). Both words relate to Purple Toothwort’s habit of hiding in dark corners though, as I found on Tuesday, this beautiful vampire is well worth seeking out.

A patch of Purple Toothwort, Lathraea clandestina.