Last year's leaves

Spring came early this year in my area and snow is almost melted already. So it is time to stock up with very useful plant material. These are dead leaves that have been laying under snow for all wintertime.
They are dirty and unsightly

But I can say that it is one of my most favorite materials. Having laid under snow the leaves become gentle and flexible and you may simply cut off  from them narrow strips with scissors to make tree branches, blades of grass, etc. Also the leaves from under snow are good material for depicting the bark of trees since they have a lot of  brown shades. Often last year's leaves have many dark spots on them and look like natural bark patterns too.

    

You can make great stones from these leaves as well

Sometime in the fall the trees shed their leaves of green color. They keep this color through to spring. You can use those leaves for depicting a grass or some marsh plants:

Pick up the leaves in the spring. They have different colors from light beige till dark brown and almost black. And then all leaves have various texture. For example, the leaves of maple (Acer platanoides) and ones of linden tree (Tilia)

  

There are times when some insects eat off fallen leaves. Then natural skeleton leaves come in. That is very useful material too. 

  

You can do monochrome artworks from them. They are applicable for making winter trees, shadows, some distant subjects. 

This is winter landscape by artist Tatyana Berdnik (Kiev, Ukraine). She used those skeleton leaves here

and artist Tatyana Sokolova (Saint Petersburg, Russia)  used the same material for her winter scene

If you will blanch skeleton leaves, it is possible to use them for making transparent curtains, clothes, etc.

Well, you need to soak your dirty leaves collected in water for a time. Then rinse off all dirt from them. Dry the leaves with paper towel and put under some weight or into a press as usually. Let them dry entirely and try to work with this great material. You will like it!
Finally very important point  is the color of last year's leaves will not turn in time. It means your artwork will have very long life.