i live in a city with barely any green area that is not in the open. the place i have in mind is a previous hobo area full of used syringes and litter. ever since the area flooded the hobos left, but there is still contaminants. I want to grow various plants in that area but im not sure if they will be safe, please tell me...

on a similar topic, i will be growing
HBWR, ephedra, chacruna, salvia, khat, calea, st johns wort, wormwood, vegetables, kanna, tobacco, and someone else will be growing cannabis.

so my second question is can these grow outdoors in the uk?

I personally doubt that you can grow most of them outdoors in the UK. Definately not cannabis. Too much rain there I think.

Also, tobacco is a really illegal plant to grow pretty much everywhere, take care with it. Don't interfere with the govs' profit

HBWR is a tropical plant that flowers after it has been growing for two years, so that's a no, the ephedra may be able to grow there but i'm not sure, that one at least will be worth a try the chacruna grows in the tropical forests of south america where it's about 30 degrees celsius all year round, so that's a no. Salvia is the same thing, a tropical, so that's a no. Khat may work, if it don't get below freezing it can probably survive the winters, because it is a slowgrowing shrub you maybe can cover it for the winter(?). Calea is also a tropical that will die(or if you're lucky, go dormant) if it gets below 15 celsius. St johns wort is no problemo, it grows wild up here in northern sweden so i think you'll be alright with that one same goes for wormwood. Kanna will probably grow down there to, try and see if it works

Hrm, The breakdowns above are accurate. I highly doubt these surroundings would be good for a garden, even a guerilla setup. I feel that the best results are achieved through constant love and care with plants, so I am not really a proponent for oddly placed gardens that you can only visit every once in a while without it being sketchy. I may be odd, but I consider my plants part of my family, my children, so I couldn't bear to not be able to visit them multiple times a day to closely observe their growth patterns, their needs, and converse with them. I realize not everyone takes this approach to gardening, but I have found through all of my past gardening experiments that constant attention provides the best results. Besides, like I said, I love them too much to have visitation restrictions .

P.S. I'm not exactly sure of your laws there, but where I live, some of the plants you listed are only legal to grow as ornamentals, so the inclusion of MJ, an illegal to possess in any form, would make it hard to convince the cops the others were for ornamental purposes if you were somehow tied to the garden, even though I understand that might be difficult to claim for a guerilla garden anyway.
Good luck in your travels. Peace.