I'm tinkering with an idea for an app to identify yard weeds, just as a personal project. I've been looking for some sort of dichotomous key (ie, "Does it have fur?" "Does it have feathers?" sort of thing), but so far everything I've found is just a list of pictures (ie Top 10 Yard Weeds in Southern US). Is anyone aware of an existing resource I could use?
Firstly, I would recommend searching the following on your browser: 'plant species identification gov'.
Also here are some resources that you might find helpful: you can search for a common list of invasive plant species in your country (such lists are available on Wikipedia, here is an example), alternatively you could use a local government webpage to search and identify invasive plant species in your specific region.
Dichotomous keys can be found on botanical/herbarium/environmental government websites, here is an example.
Lastly, apps like iNaturalist can identify plant species for you.