The original species of these tuberous plants (sometimes called Peruvian lilies) are native to South America, but they have been hybridised over the years, first with the Ligtu Hybrids and later with the Dutch Hybrids (ht 60-90 cm). They have beautiful trumpet-like flowers that are usually spotted or streaked, and they come in a range of colours including white, pinks, purple, red, orange and yellow. They can grow into very large clumps, and whilst often hard to establish in the first place, they can be very hard to get rid of if you ever want to remove them, as the roots bury themselves so deeply after a few years! They are related to the very weedy Alstroemeria psittacina (sometimes called the New Zealand Christmas bell, though it actually comes from Brazil), which should never be planted in a home garden; its variegated form is just as invasive.
Some of the taller hybrids tend to be rather sprawling, so they need to be staked - cradle stakes are ideal. They can also be grown between more sturdy plants that can give them support. There are some compact hybrids available these days (often sold as 'Princess Lilies', ht 40 cm) that are good for growing in pots, in a free-draining potting mix - perhaps the safest way to grow these plants! When planting them in the ground from a pot, do not disturb the roots at all. The taller plants flower from late spring into early summer; the dwarf ones seem to flower for longer. The blooms are excellent for picking for vases and they are grown extensively for the cut-flower trade. It is best to pick stems for vases once the buds have coloured up.
Alstroemeria like fertile, well-drained soil and do best in full sun. They suit a position in a perennial border with some of the other warm-climate flowers that do well in Sydney, such as Salvia, Dahlia and Pentas. It is best to remove the entire stem once the blooms on each are spent (or if picking the blooms for a vase), by twisting and pulling it out of the ground. This will keep the plant tidy, and new stems will grow up to replace the old ones. Fertilise the plants regularly to support their prolific flowering display (some people recommend the use of tomato food for these plants), and water them often in the growing season. It is possible to propagate them if you carefully dig up pieces and replant these straightaway, but they may take a while to settle down. These plants cope well with our hot summer weather.