Earlier in the month I wrote about Devil’s-bit Scabious, Succisa pratensis. Another British wild flower that gives a splash of late colour is Common Toadflax, Linaria vulgaris. Here in Norfolk, its yellow flowers light up grassy road verges, it also flowers along grassy rides in Breckland and I grow it in our garden.

Linaria vulgaris is a hardy perennial with stems up to 90cm (36 inches) tall, with narrow, linear bluish-green leaves all round the stem, topped with lovely yellow two-lipped flowers, like a Snapdragon (Antirrhinum majus) but with a long spur at the back. The flowers have a darker yellow or even yellow-orange centre, where the lips meet. (See the Wildflower Finder website for lots of lovely photos.) Common Toadflax can come into flower as early as June and its flowers can usually be found into late October.

Common Toadflax is widely distributed and common in England, Wales and lowland Scotland, but scarcer in Ireland. It grows in open grassy places, on stony and waste ground, in hedge banks, on road verges and railway embankments and on cultivated land, especially on calcareous soils. It is a native of temperate areas of Europe and Asia as far as China, including the British Isles (note 1).

It has been introduced into Japan, North America (Canada and United States), Australia, Chile and South Africa. The CABI Invasive Species Compendium lists countries and states where the plant is found, along with the dates and impacts of introduction (note 2). Where introduced, Linaria vulgaris can be an agricultural weed, especially in Alberta in Canada. It can also compete with native vegetation, as in parts of the United States, including Yellowstone National Park. On the plus side, its roots can help to stabilise soil.

Common Toadflax has creeping roots bearing adventitious buds and over time plants can form dense mats. They can also reproduce by seed (note 3).

Like Ribwort Plantain, Weasel’s-Snout and Sharp-leaved Fluellen, Linaria vulgaris is a member of the Plantaginaceae (the Plantain family) (note 4).

Linaria means “resembling Linum“, because the foliage of some species looks a bit similar to flax (Linum). Vulgaris means “common”. Other English names include Yellow Toadflax and Butter-and-eggs (both from the colour of the flowers).

Common Toadflax makes an ornamental and drought-tolerant garden plant, though its growth habit means you may need to keep an eye on its spread. I grew my plants from seed (from Emorsgate Seeds). Up until recently I grew them in large containers, but I have now planted some in a sunny bed in the front garden. In the past I tried to introduce container grown plants on the allotment but without success. I don’t know why they didn’t thrive – they should like sandy loam.

Linaria vulgaris has a long history of herbal use, listed on the Plants for a Future website. The plant was used as a laxative and diuretic. Extracts were used internally to treat oedema, jaundice, liver diseases, gall bladder complaints and skin problems and externally for haemorrhoids, skin eruptions, sores and malignant ulcers. However, it should only be prescribed by a qualified practitioner and should not be given to pregnant women. A yellow dye is obtained from the plant and a tea made from the plant has been used as an insecticide.

The Wild Flower Finder website lists several of the compounds found in Common Toadflax, including the lignan glycoside liriodendrin and two pyrroloquinazoline alkaloids, peganine and vasicinone.

The “toad” in the English name “Toadflax” may also relate to a medical usage. Apparently  the plants were used to treat bubonic plague and a false link may have been drawn between the words “bubo” (an inflammation of the lymph nodes) and “Bufo“ (a toad).

Common Toadflax flowers have nectar in their flower spurs and this attracts bumblebees. In Britain, only longer-tongued species such as Bombus hortorum (Garden Bumblebee) and Bombus pascuorum (Common Carder Bee) are able to get to this through the flower tube, but shorter-tongued species can overcome the problem by cutting a hole in the side of the spur and robbing the nectar without pollinating the flower.

I usually only see Common Carder Bees on the flowers but other species of bees will visit – the Emorsgate Seeds website features a Wool Carder Bee (Anthidium manicatum) hovering by a Common Toadflax plant (note 5).

Quite a few insects feed on Common Toadflax and the CABI website lists several, though it is mainly interested in them as biological control agents. One species I would like to find is the Toadflax Leaf Beetle, Chrysolina sanguinolenta. It is a rare and local insect but it occurs in Norfolk, especially in the Brecks, so if I keep on searching I may see it one day.

Notes

Note 1 – The BSBI Online Plant Atlas considers it to be a British native but the Wild Flower Finder website says that Common Toadflax may have been introduced to the UK as a garden plant. This is certainly true of its relative, Purple Toadflax, Linaria purpurea, which is native to Italy.

Clive Stace lists eight species of Linaria, plus three hybrids, in his “New Flora of the British Isles“ (Fourth Edition, 2019). Only Linaria vulgaris is native; Linaria repens (Pale Toadflax) is an archaeophyte (an alien which became established before AD 1500) and the others are neophytes (aliens which became established after AD 1500).  (Strictly, the cut off date is 1492, when Christopher Columbus voyaged to the New World.)

There are about 150 species of Linaria worldwide.

Note 2 – Information in this paragraph comes from https://www.cabi.org/isc/datasheet/30828#toDistributionMaps. CABI is the Centre for Agriculture and Bioscience International. Read more about the organisation and its work on its website: https://www.cabi.org.

Note 3 – The CABI fact sheet states that the roots are “widely but wrongly referred to as rhizomes (underground shoot structures)”. Plants “can establish from root fragments as short as 1cm long and the root system may penetrate up to one metre deep and several metres laterally, but shoots mainly originate from the shallower roots at depths of 2 – 5 cm”. Seed production and germination rates are usually low. Up to 100 seeds may form per capsule but viability may be no more than 25%.

Note 4 – Stace treats Linaria, Antirrhinum, Misopates, Veronica (Speedwells), Digitalis (Foxglove) and several other genera as the family Veronicaceae (Speedwell family).

Note 5 – We get Wool Carder Bees on Purple Toadflax (Linaria purpurea) in our garden.