Salix arctica

the colder parts of Europe, North America, and Northern Asia. 

Lovely red stems in winter hug the ground. Spring sees wee fluffy pussies that pop into yellow with the stamens ripening as in these plants as they are all males. Female plants produce prominent, erect woolly white or silky-haired catkins with bright purple-red tips or pistils. Then lush leaves in summer suppressing weeds pretty well. Finally the thrill of autumn in miniature; the leaves turn yellow.

Prostrate, variable, but this is a very prostrate form. Forms a mat. Deciduous and dioecious. These are all males. 

There are many species, I am pretty sure about this one. More on the way.

Sun or very light shade. A bit of moisture in the soil. Not waterlogged. Above a pond edge as in the Christchurch Botanic Gardens or draped over rocks to great effect. Little bulbs can poke through especially ones that come up after the catkins. 

The last image is of a variety with redder tips of immature male catkins. No evidence of this. Thanks to kodiakgarden who has posted his with permission to use it on Inaturalist. From St Lawrence Island close to Russia.