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Control Methods

Prevention and Early Detection

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.

*Follow all label instructions when using herbicides.

Flower removal

Purple loosestrife flowersWhere 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,
Water Table Management

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.

Hand pulling/digging*

Small patches of young plants can be removed by hand with little effort. Mature plants are
difficult, but not impossible to remove by digging. The root mass should be removed, making sure that ALL pieces have been collected. Purple loosestrife will re-root from the tiniest of fragments. Dormant seeds may germinate because of soil disturbance during removal activity. For these reasons, it is important to monitor the site for several years.

*To prevent the spread of seed, all work should be completed by mid-summer before flowers go to seed.

If you have any questions or constructive comments, I would love to hear from you, please send e-mail to Baldo Villegas

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Copyright© 1995-2005 by Baldo Villegas
Last updated:
Wednesday, October 26, 2005 10:08 PM