In The Garden: Thorny Unknown

This plant is growing in a schoolyard in Calgary, Alberta and I can't identify it. It is a small shrub with lots of small thorns. It is alternate and the only remaining leaf right now in March appears simple. Can someone help me to identify it? Thank you!

 

Ribes?
http://www.uwgb.edu/biodiversity/herbarium/shrubs/ribcyn01.htm

 

Ribes has a lobed leaf. Is it possible for a leaf not to lobe? There was only one at the moment. I may have to wait til Spring to see the new leaves.

 

It's possible. Need to wait for spring to get better ID's.

 

Ok. Thanks saltcedar

 

Rosa rugosa or hybrid thereof.

 

Thanks Michael