West Midlands,
United Kingdom 
Does anyone know what this plant is? It's about 4ft tall and has some spikes under each leaf. It's the only one in my garden and I have no clue what it is, plus never seen one before!
16 Jun, 2017
Answers
Super plants, great for wildlife, the bees adore them and the Goldfinches love the seeds.
https://www.google.co.uk/search?q=goldfinch+on+teasel
16 Jun, 2017
Its a teasel. The seed heads used to be used for "teasing" ie raising the nap on woven woollen materials in the old days, which is where its name comes from.
16 Jun, 2017
Suspect the seed from this one came from bird seed :)
16 Jun, 2017
Previous question
« Why are the leaves on my newly planted laburnham going yellow?
Teasel, Dipsacus fullonum, http://www.bbc.co.uk/gardening/plants/plant_finder/plant_pages/1244.shtml
16 Jun, 2017