Common Name Gooseneck loosestrife (Lysimachia clethroides), Purple gooseneck loosestrife (Lysimachia purpurea)
Genus  Lysimachia 
Species L. clethroides (Lady Jane), L. purpurea (Beaujolais)
Family Primulaceae 
Life Cycle  Perennial (USDA zones 4-9)
Tray Size  32
Plug Care Avoid exposing plugs to stressful conditions while still in the plug trays - do not allow plugs to dry out, and do not allow them to become rootbound. Harden off plants before transplanting outdoors by gradually exposing them to outdoor conditions over 5-7 days. Can be bumped up into larger cells/pots and grown on if conditions are not favorable for direct planting at time of arrival.
Netting / Staking Not required as Lysimachia can typically stand upright unsupported. However, taller stems of Lysimachia atropurpurea may benefit from light staking in windy conditions or high-density plantings. One layer of agribon should suffice in these situations. 
Temperature Range Both species are hardy and tolerate a wide range of conditions, thriving in temperatures between 55-85°F. In hotter areas, plants benefit from high irrigation, or being planted in a low-lying area that is always wet. 
Spacing

Beaujolais - 12-18" Lady Jane - 18-24"

Soil Preference Beaujolais prefers moist, humus-rich, well-draining soil with a neutral to slightly acidic pH (6.0-7.0). Lady Jane tolerates heavier soils and wetter conditions, making it ideal for swampy or low-lying areas.
Day Length These perennials are day-neutral, and should be planted in full sun. They can tolerate some light shade in southern zones. 
Pinching Pinching is not necessary, but can be done early in the season (a few weeks after planting) to encourage bushier growth and more flower spikes in year one. 
When to Plant These are vernalized plugs that can be planted in the spring as soon as the ground is workable. They are frost hardy as long as there is no vulnerable, tender new growth. If the plugs have broken dormancy and are actively growing, protect new shoots from frost. Actively growing plugs can be planted all season until early fall. 
Harvesting Harvest when 1/3 to 1/2 of the florets on a spike have opened. Cut stems early in the morning using sharp, clean tools. Remove any foliage that will be below the waterline.
Post Harvest Care Place stems immediately in clean, cool water. Change water every 2-3 days to prevent bacterial buildup. Both species have a vase life of 5-7 days and benefit from floral preservatives to extend freshness.
Diseases / Insects These plants are typically resistant to pests and disease. They may occasionally succumb to aphids, thrips and other common and widespread plant pests. 
Bailey's Notes

Lysimachia atropurpurea 'Beaujolais' is a cool looking plant! Its rigid spikes in rich burgundy just look fancy! Grow it in rich moist soil and it will form large clumps giving you plenty of cutting material.

Lysimachia clethroides 'Lady Jane' is an improved form of this vigorous species. It can get a little out of control in damp soil so be careful where you plant it! That said, it will provide you with more cutting material than you know what to do with after a couple of years. The graceful nodding stems add texture and whimsy to floral design and I think they're positively lovely. 

Resources

North Carolina State Extension: Lysimachia Profile

Royal Horticultural Society: Lysimachia Growing Advice