little black bugs smothering my plants!

Hi,  I seem to have these little black bugs smothering nearly everything! some people say wipe them off or blast them with the hose but I think that'd wreck the plants... they're on delicate flowers (jasmine, bishops flower, some small cosmos etc.

I don't like the idea of using pesticides or washing up liquid... are there any other options? plus what are they and why are they hounding my garden? I also took on an allotment this year and inherited an artichoke plant but the artichokes on it are being choked by these black buggies too!

Im a new gardener & am dismayed that my plants are like this!! 

Please help/ advise!