L- Common Dandelion plant R-Atypical Dandelion flower lacking ligules
Common Dandelion (Taraxacum officinale) is a European species that is naturalized in Michigan. First recorded in the wild in 1837 when it was already well established. Brought here by the earliest settlers as a winter source of greens high in vitamin C they were eaten in the winter and early spring to prevent scurvy. The specific name officinale means “of the shops” and alludes to this useful plants value as a cash crop.
L- Dandelion flower head R- Dandelion seed head
Dandelions are distinctive when in flower or seed. Be careful if you gather plants for greens. They are best when just coming up before they flower. Their deeply toothed leaves and milky juice help to distinguish them but there are look-a-likes. And of course never gather greens from lawns that have had chemicals sprayed on them.
L-Sectioned Dandelion seed head R- Ray floret with parts labeled
What most people call a Dandelion flower is actually a many flowered head. This is true of all members of the large Aster (Asteraceae) family. At the base of a Dandelion head is a group of green bracts called the involucre. Dandelions have only one type of flowers, ray florets. Some members of the Aster family, for example daisies, have ray and disk florets. Ligules are the “petals” of the dandelion flower. Rarely you will find Dandelions where they are absent. The fuzzy ring at the base of an individual flower is the pappus. This develops into the feather-like structure of the seed. Pappus characteristics are needed to separate some species in this family. The involucre is composed of the phyllaries which are the green bracts under the flowers. The florets are held in the receptacle. See Brian Johnston’s post on Microscopy-UK for more photos including some great microscopic images.
Go outside, pick a dandelion flower head, and take it apart. Look at the tiny flowers under a magnifying glass. Try to find the pappus. Understand the structure of this flower head as a first step to learning about the fascinating Aster Family.
Copyright 2015 by Donald Drife
Webpage Michigan Nature Guy
Follow MichiganNatureGuy on Facebook
Nice! Thanks for the review about places where the word “ligule” can be used… Ron G.
Dandelions actually have “Ligulate” florets, not ray florets. Ray florets are only found on Asteraceae species with a Discoid head (composed of ray and disc florets) and Radiate heads (composed of only ray florets). The dandelion is an example of a ligulate head, containing only ligulate florets.
I use the term ray florets because it agrees with Ed Voss’ use in the Michigan Flora. He states, “Ray flowers are sometimes also called ligulate, especially in the tribe in which all heads consist entirely of such ligulate flowers.” Many readers of my blog consult the Flora and I try to use the terms as they are used there.
Thank you for this gracefully written article. I’m a writer and came here needing to know how to describe the seed head.
The scientific description didn’t quite work for my story; woman has blonde curly hair that reminded me of that seed head.
I called it a dandelion orb, which I hope will not offend the purists.
Still glad to know and glad to have found this resource!
Thanks!