The Right Place
Purple loosestrife is hardy from Florida to Canada (zones 9 to 3). It is able to withstand winter temperatures as cold as -20°F or more.
Planting Nursery Stock
These plants like full, half day or filtered sunshine and moist soil. They are happy anywhere these conditions prevail. They can handle extremely wet, boggy soil, typical of lake and wetlands regions as well. Plant nursery stock in the spring or fall. If planting in the spring, wait until all danger of frost is past and the soil is warm and dry enough to work. Loosen it by digging around with a trowel down to about 8 or 10 inches, removing stones or other debris. Remove each young plant from its container and dig holes large enough to accommodate the soilball. Set each plant in the hole so that it is at the same depth in the ground as it was in its container. Fill any space around the soilball with soil and firm it gently around plant stems. Water generously at planting time and for several days thereafter until the plant is established. Pinching branch tips back will encourage the plant to branch and become fuller. Allow 2 or 3 feet between each loosestrife plant, as they will spread rapidly.
Amendments In Planting or Transplanting
There are a number of products at the garden center that will help your newly planted or transplanted plants deal better with the stress inherent in the planting process. All healthy plants have beneficial fungi, called mycorrhizal fungi, living on their roots. You can buy these valuable additions to your plant’s ecosystem. See the file describing Using Micorrhizae When Planting.
In addition, there are a number of products such as seaweed, compost tea, and beneficial soil microbes that when added to the planting process will help your newly established plants get going faster. See the file New Technology In Plant Growth Activators