as everyone else has said teh top one is japanese knotweed. an invasive species here in the UK. a section as small as your thumbnail can sprout a new plant and as such it's generally advised to inform the local council of it's whereabouts so that they can clear it and prevent it's spread as it is harmful to local habitats as well as infrastructure (it's been reported to grow through concreate and tarmac)
the seccond one, my first guess would be hymalayan balsam (again an invasive species, and I spent much of last thursday ripping it out from a patch of local woodland as part of a woodland managment project with a local conservation charity) though on the plus side it's sap is supposedly good for treating rashes (though I've also heard that it can have adverse effects on sensitive skin)
it could also be rosebay willowherb (aka fireweed) which has a simalar appearience until they flower (willowherb has purple/magenta flowers on the end of narrow "stalks") personally to me it looks more like willowherb than balsam from the pictures