* Taraxacum officinale (syn. T. officinale subsp. vulgare), Common Dandelion. Found in many forms, but differs at least from the following species:
* Taraxacum albidum, a white-flowering Japanese dandelion.
* Taraxacum japonicum, Japanese dandelion. No ring of smallish, downward-turned leaves under the flowerhead.
* Taraxacum laevigatum (syn. T. erythrospermum), Red-seeded Dandelion; achenes reddish brown and leaves deeply cut throughout length. Inner bracts' tips are hooded.
Seed development and genetics
Macro photo of dandelion seed dispersal.
As aforementioned, the taxonomical situation of the genus is quite complex, mainly because many dandelions are genetically triploid. An odd number of chromosomes usually is associated with sterility , but dandelions with this karyotype can reproduce without fertilization, a process called apomixis [2]. In these individuals flowers are useless vestigial structures, although they may still produce a small percentage of fertile pollen, keeping some genetic contact with sexual individuals. Diploid dandelions develop seeds after cross-pollination and are self-incompatible. In most zones of southern Europe and Asia, dandelion populations are sexual or mixed sexual-apomictic , while in northern countries only triploid and tetraploid apomicts are present, as is in the zones where it is not native. This seems to be linked to higher temperatures, survival of pre-glacial populations and human impact, but the subject is still being studied.
There are usually 54 to 172 seeds produced per head, but a single plant can produce more than 2000 seeds a year. It has been estimated that more than 97 000 000 seeds/hectare could be produced every year by a dense stand of dandelions.
source : hydroponicsearch
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