What is this plant? It looks like a weed to me. But I've never seen it before. It's growing in my front yard, and we were so intrigued by it that we didn't pull it out. now it's about 6 feet tall. It has velvety leaves, and yellow flowers grow out of this thing on top that looks like a corn cob, but only a few come out at a time and then they fall off. See pictures below:
Weeds are a matter of definition. An Oak tree in the middle of a corn field could be considered a weed by definition of what a weed is. It could be considered to be an undesirable plant in a place where it is not necessarily wanted. Most of what we usually consider weeds in the garden though are ruderals.
Great Mullein Verbascum thapsus: http://ip30.eti.uva.nl/BIS/flora.php?selected=beschrijving&menuentry=soorten&id=3577
To echo what anza said, I was always told that 'a weed is just a plant in the wrong place'. Short and sweet!
But what is a "wrong place"? Do you measure it objectively (native = right place, invasive alien = wrong place), or subjectively ("I don't like it there, regardless of whether it is native or invasive")?
I can understand gardeners - it is a matter of their tolerance and practical goals. But I was surprised to see botanists using this as a feature in identification keys: 1 - Plant weedy. (2) 1' - Plant native. (3) As if I would be able to tell one from another by just looking at the plant...
I live in Kamloops BC, and I see them in the native grassland where the soil has been disturbed. We are in a semi-arid area, and they seem to thrive!
I guess its up to each individual as to what is regarded as a weed. If its something you don't want for any reason, then it could be considered a weed. Even something beautiful in its own right. An example in my garden would be sun flowers. Masses of them came up in a border where I had bird feeders set up over winter. Giant sunflowers look wrong immediatly above a sunken patio. Therefore, I weeded them out.
To me a weed is a plant growing in a place where I do not want it to be and that I do not want to save to plant it in another place or give it to others. Gomero