In an article on vestigial organsLive Science writes: “Dandelions, like all flowers, have the proper organs (stamen and pistil) necessary for sexual reproduction, but do not use them. Dandelions reproduce without fertilization; they basically clone themselves, and they are quite successful at it. Look at any lawn for the proof. If dandelions were to revert to sexual reproduction, they might not retain whatever traits they have that allow them to be pests to gardeners everywhere.”

Live Science

Editorial Comment The Dandelion is a good example where reproduction can be achieved in many ways and one dominates. Likewise grapes can take root wherever a vine touches the ground and can spread successfully this way as well as being propagated by seed. Dandelions can reproduce sexually and their stamens and pistils are fully formed and functional, so there is nothing vestigial about them. However, dandelions can reproduce themselves without being fertilised by a pollen carrying insect, by a process called apomixis. This method of reproduction is a back-up system in many plants. The fact that dandelions do it in a particularly efficient way does not make their flower parts vestigial. Dandelions that reproduce by apomixes are triploid, i.e. have three sets of chromosomes, instead of the normal two. As explained in an article on the Killer Plants website:
“At the base of each flower is a single ovule which will develop into a seed. If the dandelion has a normal complement of chromosomes, it is a diploid. These diploids undergo meiosis, the reduction process where only one half of the chromosomes remain in the cell. They produce seeds by the fertilization of the ovule with the gametes (sex cells) from the pollen grain. But many dandelions are polyploid, usually triploid. These triploids (3 sets of chromosomes) do not undergo meiosis. Most triploid plants can never produce seed, but the dandelion sets seed by a process called apomixis (apo – away from; mixis, act of mixing). The triploid ovule avoids meiosis, keeping the complete complement of the mother’s chromosomes. The unreduced egg cell develops into an embryo. The embryo (young plant) within the seed is a natural clone, genetically identical to the mother plant.”

Evidence News, 7 October 2009

For more information on vestigial organs see the Creation Research article Vestigial Organs. PDF here.