The garden of the Casa da Cerca art centre in Almada (just across the River Tagus from the main city of Lisbon) is a pretty garden with a small amphitheatre, a woodland area and a lot of plants which can be used to create art supplies.
I learned that a lot of familiar plants can provide paper, oils and dyes for use by artists. Below you'll see tea tree (for oil); onions, ivy, iris and fennel (for dye); broad beans (for dye and paper) and castor-oil plant (for oil and paper), finishing off with a shot of the workshop where they put these plants to use:
When I visited (January 2018) there was also a section of the garden devoted to the five senses. I somehow failed to capture a photo of the "smell" section but here are the others: