Common Name Alstroemeria, Peruvian lily 
Genus  Alstroemeria 
Species A. pelegrina 
Family Alstroemeriaceae
Life Cycle  Herbaceous Perennial  
Tray Size  18
Plug Care You will likely receive these plugs as actively growing plants. They should be hardened off and planted out immediately if the chance of frost has passed, or bumped up into larger pots and grown on. Do not hold for a long period of time in the containers they arrive in or else they will become rootbound. 
Netting / Staking Not necessary for the Summer Paradise cultivars. 
Temperature Range Cold hardy to at least zone 7b (and possibly as cold as 5b - trial at your own risk!). The Summer Paradise series is tolerant of hot and weather as well, making them suitable for a wide range of climates. 
Spacing 18-22"
Soil Preference Loose, fertile, moist but well draining soil. They require regular irrigation and fertilization to stay productive all season long. 
Day Length Plant in full sun, some partial afternoon shade in hot summer climates is OK. 
Pinching Not necessary. 
When to Plant Plant in the spring after all danger of frost has passed. If the plants come in a dormant state they can be planted before the last frost and will wake up and grow as the temperature warms. New growth must be protected from frost. 
Harvesting Depending on your zone and the point at which these perennials come out of dormancy, the Summer Paradise series has the ability to flower from May through to November, or first frost. To harvest alstroemeria it is better to tug and twist the stem to harvest, similar to how you harvest rhubarb. Do not use snips to cut the stem. Harvesting this way encourages the plant to develop new bloom spikes. 
Post Harvest Care After pulling the stem to harvest, snip the end off the stem to get a clean cut and immediately place into cool water. Store in a cooler at 36-38F for up to a week - vase life is approximately 2 weeks. Alstroemeria are very ethylene sensitive and exposure to the gas can cause premature flower fall and translucent petals. Use a floral preservative to maximize vase life and insure not all leaves are removed from around the flowers as they aid in water uptake and hydration. 
Diseases / Insects

Overwatering and Overcrowding can promote the development of fugal issues (leaf spot, fusarium wilt, anthracnose) which will present itself with spotting on leaves or mold growing on and around the roots. Cutting stems instead of the recommended harvest technique of twisting and pulling will leave behind plant residue that will rot and can lead to fungal issues. 

As with most of our crops, alstroemeria are susceptible to aphids, white flies and thrips. Slug and snail damage can be an issue in wetter areas. 

Bailey's Notes

The early generations of Alstroemeria weren't very well adapted to US growing conditions. They tended to not be very winter hardy, and not very tolerant of summer heat, which made them unsuitable for most of us.

The Summer series may be what we have been waiting for. They are hardy at least to zone 7b (and possibly as cold as 5b- trial at your own risk!), aren't bothered by summer heat, and they're tall enough to cut! As they mature they will reach 3' in height. They also keep blooming all summer long as long as you keep cutting them. They do require regular water and good drainage.

Alstroemeria, or Peruvian Lily were brought into cut flower cultivation in the '90's and then immediately became a mass-market darling because of their broad color range and extremely long lasting nature. 

Resources

Post Harvest Care 

Grow Guide