Hi all I planted alstroemeria in container last year
It's been a very harsh winter Now I'm seeing this in the container
Weed or alstroemeria coming back ???

Definitely not alstroemeria

thank you
Can I use this soil to plant some other plant ?

Yes, you can use the soil again.

Any plant that is outdoors can acquire seeds other than what was planted; some seeds are blown on the wind and some are a gift of the birds.

Horseweed? If so, destroy it. One of the ugliest most pestilential weeds I know of.

Looks like Horseweed and a dandelion. No alstroemeria in sight.

I think the consensus is ... Well sorry to say ..it's a weed! Bummer!
So many alstroemerias spread by rhysomes in the hardy types. Can did down gently to see the root ball . The weed has a tap root and alstroemerias will have a root ball & possibly could still be in the pot. I love them & grow the orange color. They come up every year and spread well even in hard pac clay soil. Tough little guys!