Our mystery seeds from last week were from the spiny sowthistle, Sonchus asper.
The seeds come from these fluffy clusters that may resemble dandelion seed heads.
The yellow clusters of ray flowers also look quite a bit like dandelion flowers.
Sowthistles are much more upright than dandelions, however, because they have a distinct stem.
The leaves of the spiny sowthistle have "prickles" and the leaves of sowthistles wrap around the stem at the bases.
They can make and spread a lot of seeds in a short period of time.
Do sowthistles grow where you live?