This flowering tobacco plant, a native of Brazil, is often grown as an annual, though it is really a frost-tender perennial and will survive for a few years in our Sydney climate. It can grow around a metre tall. It has large soft leaves and flower spires massed with a haze of tiny lime-green tubular bells which can appear almost all year round, but particularly in the warmer months. The flowers feel slightly sticky. It prefers a sunny spot (though will also flower reasonably well in part shade); it is indifferent to soil type, often coming up in cracks in paving. In some gardens it will self-seed with abandon, though in others it never reappears. This may be a result of heavy mulching suffocating the tiny seeds. Like all lime-green plants, it looks brilliant with blue, purple or orange flowers, or against a background of dark purplish leaves. It is useful as a cut flower. It is rarely available in nurseries, but many keen gardeners have it and will give you a seedling if you ask. Sometimes Nicotiana will grow from cuttings, so that's worth a try too: keep the cutting in a humid, enclosed environment until it (hopefully) strikes.
The genus belongs to the family Solanaceae, which contains a number of poisonous members, and Nicotiana plants should never be ingested (or smoked!). Contact with the foliage may irritate skin, so gloves should be worn when handling the plants.