> not all weeds are invasive (i.e. non indiginous)

I believe you are mistaken or confused. You also misspelled indigenous.

Invasive typically refers to the propensity of a non indigenous species (~= "plant that comes from somewhere else") to spread and replace or out-compete for resources such as light, nutrients, water, etc. other species that are indigenous species. At least in my travels, it is exceptionally rarely used in a broader sense to mean "any non-indigenous plant" (as adopting this sense would, for example, include pretty much every single garden plant ever, every food crop ever, etc. and thus be of dubious to zero utility).

An endemic (~="was always here and here only") species is not a weed, to a botanist, by definition, because it was always there and there only.

An indigenous (~="was always there") species is not a weed, to a botanist, by definition, because it was always there.

We often substitute the word "native" for indigenous in Australia and New Zealand, but in Australia this has an alternate meaning which is "comes from anywhere in Australia (not necessarily this specific area)" and therefore in an Australian context a "native" can be non-endemic, non-indigenous, and even invasive. An example of an invasive native would be Acacia longifolia when found in its non-indigenous range in Western Australia.

A weed in common use as a botanical pronoun by the general public most usually refers to any plant which is both invasive and non-indigenous. Any plant which is non-indigenous (but not significantly invasive) may also often be referred to as a weed by environmentalists, ecologists, and botanists (or anyone else), depending upon their mood, company and character.

I hope this helps clear up any confusion.

Sincerely, card carrying member, Australian Plant Society.

Thanks for pointing out the speeling error.

I think we agree on the terms "invasive," "endemic," and "indigenous."

We part ways on the meaning of "weed." To my understanding, a weed is simply a plant that is growing where we did not isn't it and where we do not want it. Especially if it outcompetes what we do want there. Merriam-Webster's definition of "weed": http://www.merriam-webster.com/dictionary/weed and "A weed is defined as a plant out of place and in pastures they may be toxic or unpalatable, compete for light, moisture, and nutrients, and take up space needed for desirable species. However, some weeds at certain growth stages can be nutritious." (pdf) https://www.nrcs.usda.gov/wps/cmis_proxy/https/ecm.nrcs.usda...

> both invasive and non-indigenous.

As you pointed out, all invasive species are non-indigenous. That's criterion 1 at https://www.fs.usda.gov/wildflowers/invasives/index.shtml

That's nice for the Australian Plant Society, but I assure you in the various parts of the US that I have lived in, native plants that people don't want in their sterile patches of grass are also definitely considered weeds.

It's a term used for anything smaller than a bush or tree that people don't want in their yards. Official definitions be damned.

Yes, the joke here too is that in common use "weed" just means "plant that is not wanted by the speaker", but it is considered both incorrect and unlearned to call an indigenous plant a weed and would be quickly corrected/retracted here if popularly used, for example in media.

Perhaps in Oz. In the States, however, this is the correct usage. Being native or even indigenous does not prevent it from being a weed.

And not all invasives are weeds, surprisingly.

I recently learned that people commonly use privets as a bush or hedgerow around me in North Texas, but they are invasive in wooded areas. DFW has the largest urban forest in the US but 40% (and counting) contains privets.