Alstroemerias are not true bulbs - they are a rhizomatous perennial that produces a mass of brittle, fleshy roots that are actually moisture storage organs. Look for them as potted plants in season at your local nursery or by mail order from better perennial sources. Be warned that many of those hybrids grown for the cut flower trade are not hardy in zones lower than 9, but you can find a few hardier hybrids available as well as the species A. aurea, auranitica and psittacina. If happily sited, these can spread rapidly from seed and are extremely difficult to move once established, so proceed with caution.

'Sweet Laura' overwintered in a ground for me in z6.
I can't say it's very floriferous, but otherwise is very healthy.
It was bred in CT.
'Freedom', on another side, despite being promoted as z5b plant, didn't survive last very warm winter.

My alstroemeria overwinters for me in zone 6b. If I remember correctly, I bought it at White Flower Farm. I bought 3 plants and 2 didn't overwinter, but the third did and has come back reliably for about 6 years.

I didn't mean to imply that alstroemerias would not be hardy for you......some varieties have considerable cold tolerance and that selection is increasing - Sweet Laura, Freedom, Glory of the Andes, even psittacina should be good to zone 6, perhaps even lower. But these are NOT the same as those varieties used in the cut flower trade and you will not have as wide a selection of colors as offered by the cut flower types, many of which are grown in southern California or imported from Chile and Peru.

And the selection of those hybrids hardy in zone 8 and above has increased significantly in recent years - the Princess Lily collection and the Inca collection offer a much wider color range than was available previously, but on pretty low growing, compact plants. These may not be widely available outside the west coast and may be of marginal winter hardiness in zone 8. I'd certainly consider a good winter mulch.

Alstromerias - both species and the Inca range - will grow and flower in bigger containers.

Totally agree that they have the potential to be weedy - and very tenacious. Deadheading is strongly recommended. Dispose of surplus roots with great care. It's amazing what will survive as a weed when a gardener has given up!

In z9 they are happy in sun and some shade. They'll grow in shade but don't flower well. (In a 'woodland' environment.)

Probably an annual repot (if I was being kind!). The 'Incas' flower for AGES and seem to age quite prettily, too.

I've tried numerous times to grow these from seeds, only to have them die after transplanting. The best place I've seen to buy them is Plant Delights Nursery. It may seem like you're paying a lot more for your plants, but the size and quality more than make up for it. Also, their zone ratings are reliable. They test everything in their garden, and will also tell you when they think you can "push the zone" on certain things.

HW

Here is a link that might be useful: Plants Delight Catalog