Lily of the valley "Convallaria majalis"

Known by the scientific name Convallaria majalis, the lily of the valley is an herbaceous (the leaves and stems die at the end of the growing season and there's no persistent woody stem) perennial foundin temperate areas of the Northern Hemisphere. The plant forms large colonies by spreading underground stems and appears above ground with upright stems called pips. The lily blooms in the late spring and has white, bell-shaped, sweet-smelling flowers and small orange-red berries.

The plant pops up in Christian legend several times. As the story goes, lily of the valley was formed from the tears of Mary as she wept at the crucifixion of Jesus, and grew from the blood shed by Saint Leonard of Noblac during his fight with a dragon. The lily of the valley was also used as the floral emblem of Yugoslavia and is the national flower of Finland

Is it really poisonous?

Toxicity is the plant's defense against animals eating its seeds. All parts of the plant the stems, the leaves, the flowers and the berries are extremely poisonous and close to 40 different cardiac glycosides have been found in the plant so far.

Glycosides are chemical compounds where a sugar is bound to a non-carbohydrate molecule. By increasing calcium stores in and around cells, cardiac glycosides increase the force with which the heart contracts and the volume of blood it can pump. This is not necessarily a bad thing, and these compounds have been used in medicine since the ancient Roman Empire to treat arrhythmia and congestive heart failure (today, the drugs Lanoxin, Digitek, and Lanoxicaps are made from a purified cardiac glycoside extracted from the foxglove plant). In quantities over the recommended safe dosage, though, cardiac glycosides can wreak havoc on your gastrointestinal, circulatory and nervous systems (more on that later).

Lily of the valley "Convallaria majalis" can be fatal if ingested, especially to children. The method of action is through cardiac glycosides, which create an effect much like exposure to that of Digitalis, found in foxglove. The plant is classified as a “1” on the poison scale, which means it has major toxicity that can lead to death. It is also a “3” due to its often severe dermatitis. 

Experts recommend calling a Poison Control Center or calling 911 if any part of the plant is ingested. Convallatoxin and convallamarin are two of the main toxic glycosides in lily of the valley, but there are numerous others as well as saponins, which have not been well researched and whose method of action are not fully understood. 

The overwhelming effect is one of a cardiac episode. As little as two leaves of the plant can be a fatal dose in young children and pets. If this plant is present in your landscape, it is wise to remove it. This can help prevent any accidents with lily of the valley poisoning and keep the garden safe for everyone.