Prevention and early detection are our best tools in stopping purple loosestrife invasion and spread. Purple loosestrife should be removed and destroyed by bagging plant material and allowing it to completely dry out, by burning or burial, before disposing. Potential habitat should be searched annually during July and August (peak bloom when easily detected). The discovery and early eradication of new infestations while still small is both economically and environmentally cost effective.
Careful use of herbicide has been proven to be an effective, efficient, and the least destructive means of removing large purple loosestrife stands. Available herbicides registered for use in California are limited. The most widely used is spot treatment with Roundup and Rodeo (glyphosate) at
a 1-1½ % solution, during early to late bloom.
The use of 2,4-D has shown inconsistent results. Garlon 3A or Renovate
(triclopyr), selective for broadleaved plants, has yet to be approved
for use in California.
Where plant digging is not feasible, removal of flower stalks helps retard the spread of seed. A single plant can produce 2.7 million seeds per year. Each seed can lay dormant for years in the soil before germinating. Therefore, where removal of flowers is feasible it is not a trivial exercise.
Cutting, Mowing, Fire,
Many mechanical and cultural methods have been tried and have proven ineffective in controlling purple loosestrife. In many cases mechanical methods and controlled burns have resulted in the promotion of further spread.
Small patches of young plants can be removed by hand with
little effort. Mature plants are