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PlantRight™ uses scientific criteria and direct observations to make objective recommendations about invasive plants. When there are unanswered questions about a specific species, PlantRight has partnered with scientists and/or launched investigations to better understand the plant's potential to invade California's wildlands. This careful consideration assures gardeners and businesses alike that the recommendations from PlantRight are based on credible research and thoughtful analysis.

For more information about this research, click on the below categories to learn more.

PRE Tool - Identifying Invasives Before They Spread

Once invasive plants establish in natural areas, it becomes much more difficult and costly to control their spread. By simply choosing noninvasive alternatives for our yards, the impacts caused by horticultural invasives can be easily avoided.

PlantRight has worked with researchers at the University of Washington, and at the University of California, Davis to develop a method for determining a plant species’ potential for becoming invasive in California. PlantRight's Plant Risk Evaluation (PRE) tool is an adaptation of a broader screening tool that allows for highly accurate (98%) determinations on the invasiveness of horticultural plants.

For more information about the PRE model and research, you may wish to review this March 2015 PLoS ONE publication here.

Ongoing Research About Plants Already in the Trade

Each invasive plant undergoing research has a unique, unanswered question about its biology or invasiveness:

  • Ivy is invasive in many natural areas across the state. But there are three species of ivy that are of concern: Algerian ivy (Hedera canariensis), English ivy (H. helix), and Irish ivy (H. hibernica). English ivy alone has hundreds of varieties that are for sale. Ivy can be impossible to correctly identify in the wild, even to the trained eye – and it is typically unclear which type of ivy is the one invading natural areas! It could be that only a few species/cultivars are invasive while others are safe for planting. We hope that future research will discover which plants are invasive, in hopes that we can discover the bad players and still use the benign forms in our gardens and landscaping. Please consider using an alternative to ivy if you live along the coast or near inland waterways.
  • Research is in progress to examine sweet broom (Genista racemosa or Cytisus spachianus), which was developed as a sterile hybrid and might provide a safe alternative to invasive Scotch or French broom. Questions on sweet broom include whether it is truly sterile and whether plants labeled as sweet broom in nurseries are truly this hybrid rather than the invasive species.

Questions remain on some species. For some plants, we need more information on the extent of their invasions. We know that others are invasive in certain areas of the state and are working with the horticultural industry to examine the level of their importance to the industry and to determine appropriate alternatives. Washington palm (Washingtonia robusta) and Brazilian peppertree (Schinus terebinthifolia) are examples that are invasive along waterways in Southern California. PlantRight would also like to determine which species or varieties of cotoneasters (Cotoneaster franchetii, lacteus, and pannosa) are responsible for the invasions of cotoneaster in natural areas, and if they are a significant part of the horticultural trade.

Didn't find what you were looking for? Try reading our Frequently Asked Questions. You can also find more sources of invasive plant research in our library of peer-reviewed articles. If you still have questions, please contact us.