There are more than 240 different Dandelions. They are divided up into 9 sections, which may flower at differing times.
Section Ruderalia with 121 members has large flowers, flowers from January to December, and is the common Dandelion of meadows, waysides and grassy places.
Section Erythrosperma with 30 members flowers from April to June, and are generally the smallest and thinnest Dandelions. Preferring warm dry sunny places the habitat is chalk grassland, heaths and sand dunes.
Section Celtica with 35 members prefers damp meadows.
Section Hamata with 18 members is very weedy. The leaves are hooked at the tip.
Section Naevosa with 12 members preferring the north and western regions. The leaves have many dark splodges.
Section Taraxacum with 6 members prefer mountains and have bright green leaves.
Section Palustria with 4 members have appressed pale-bordered bracts below the flowers.
Section Spectabilia with 3 members prefers damp acidic soils on the hills.
Section Obliqua with 2 members have deep or orange-yellow flowers preferring coastal regions.
Lookee-Likees : A great many other Dandelions, about 250.
Superficial resemblance to: Cat's-ears,
Hawk's-beards but these usually have branched stems that are both hairy and bear leaves.
Uniquely identifiable characteristics: They all have single un-branched and hollow stems that are leafless and which exude a milky sap or latex on breaking. They are all low, with a basal rosette of long and usually lobed leaves, and the flower head is always yellow or yellowish orange. Dandelion is the only member of the yellow member of the Daisy & Dandelion Family to have a hollow stem.
Between the 250+ odd different varieties of Dandelion, there is always at least one that is in flower at any one time. That is, between them, they flower all year round. But there is a lull around cold winters when no dandelion is in flower. It is very often the during the absence of any dandelions in flower in February and March when you are able to spot the first flowerings of Colt's-foot, which has Dandelion-type flowers, but the petals are much thinner, which otherwise would be hard to spot amongst the myriad of Dandelions. Colt's-foot flowers at least 3 weeks earlier than do Dandelions.
An observation by a friend is that, between them, Dandelions and Daisies seem to take it in turns to smother fields, one year full of Daisys, the next Dandelions. It could be that both rootstocks are present in the ground at the start of the year, and the one which comes to dominate in Spring is dependent upon the particular weather present at the flowers' respective growing weeks. If its warm when Daisies wish to grow or cool when Dandelions wish to grow, then Daisies may win out that year, or vice versa. Whichever dominates first will shade the other into submission. Of course, there may be signalling phyto-chemicals involved too, the one suppressing growth of the other.
Dandelions (as well as Brambles (Rubus, Hawkweeds (Hieracium) all have hundreds of species. They are all apomictic (or agamospermic - asexual reproduction via seeds), capable of the production of viable seeds without self-fertilisation or cross-fertilisation and are entirely female in origin. Plants growing from these seeds are clones. This process results in a wide spectrum of hybrid microspecies, most looking very similar. All or most species of Dandelion are hybrids which reproduce asexually - only a handful reproduce by sexual means. Hawthorns (Cratageous), Rowans & Whitebeams (Sorbus), Meadow-grasses (Poa) and
Lady's-mantles (Alchemilla) are also apomictic with dozens of very similar hybrid species.
Although there is only one flower atop each leafless stalk, there can be very many stalks arising from a single basal rosette of leaves. Cunningly, they don't all rise at once, but keep a low profile amidst the grass and take turns at growing, especially just after mowing, such that there is always one stalk ready to set seed when the gardener has been away for just a day!
No one has ever seen a dandelion where half of the flower is yellow petals and the other half a seed clock. So secret and sudden is the metamorphosis from flower to seed that some people think that they are two different plants! One day the flower closes up for the night one last time, enshrouded by its sepals, and in the morning miraculously opens up as a seed clock.
The roots can be dried, ground and roasted to make a caffeine-free coffee substitute, sold as Dandelion Coffee by various health stores.
A very interesting drink can be made with Dandelion and
Burdock sold as 'Dandelion & Burdock' by the only remaining Temperance Bar in England, who reside in Rawtenstall, Lancashire. It seems to be illegal to make Dandelion and Burdock at home, this being possibly due to the hepatotoxic Pyrrolizidine alkaloids present in Burdock which the brewer may un-wittingly incorporate into the brew.
The nick-name pissabed is due to the diuretic effect after drinking potions.
A close relative of Dandelion,
Russian Dandelion (Taraxacum kok-saghyz) aka Rubber Root (which is a yellow dandelion not native to the UK) and which once used to be harvested during the second World War for the milky latex it produces. This latex can be used as a substitute for rubber latex which was scarce during the war. But as the milky latex seeps out from the stems, it is quick to polymerize into a much more viscous substance, so it had to be used quickly. It has now been genetically modified so that the enzyme responsible for the rapid polymerisation is switched off, and it also now produces up to five times more latex. The latex is hoped to be used to replace rubber latex from trees, which are succumbing to a fungal infection in many parts of the world where rubber trees are harvested for their latex. This plant also produces a diabetic-safe sugar called Inulin which can also be harvested.
Dandelion contains the allergen Taraxinic Acid, another Sesquiterpene Lactone, which may have application in the treatment of leukaemia. Dandelions have been known to cause allergic reactions and contact dermatitis due to this toxic component.
Tetrahydroidentin B is another sesquiterpene lactone found in Dandelions, and is a plant secondary metabolite.