The California Horticultural Invasives Prevention (Cal-HIP)
steering committee, the group behind PlantRight, uses objective, scientific
criteria and direct observations to make recommendations about invasive plants.
When there are unanswered questions about a specific invasive plant, Cal-HIP
has launched investigations to better understand the plant and its potential to
invade our wildlands.
This careful consideration assures gardeners and businesses alike that the recommendations from PlantRight are based on credible research and thoughtful analysis.
Each invasive plant undergoing research has a unique, unanswered question about its biology or invasiveness. Read below how we are working to promote research that will provide scientific information on the following plants:
We know that some forms of pampas grass (Cortaderia jubata and C. selloana) have invaded natural areas, especially along the coast. But some cultivars of Cortaderia selloana are thought to produce very little seed, which may mean that they do not contribute to invasive populations. Discussion with academic experts, environmental groups, and horticultural business leaders outlined the next steps for investigation into the reproduction and dispersal of named cultivars of pampas grass. Research will determine if sterile and low-fertility strains of Cortaderia selloana are safe to use in the horticultural trade. This information can help the horticultural community to make sound decisions about these grasses. While this research is being conducted, please consider using one of the featured alternatives to pampas grass if you live along the coast or near inland waterways.
Some form of ivy is invasive in many natural areas across the state. But there are three species of ivy: Algerian ivy (Hedera canariensis), English ivy (H. helix), and Irish ivy (H. hibernica). English ivy alone has hundred of varieties that are for sale. Ivy can be impossible to correctly identify in the wild, even to the trained eye – and no one knows 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’re researching these ivies to 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.
Cal-HIP is conducting economic research and wildland sampling and identification of cotoneasters species (Cotoneaster franchetii, lacteus, and pannosa). The group is trying to discover which species or varieties are responsible for the invasions of cotoneaster in natural areas, and if they are a significant part of the horticultural trade.
A familiar wildland invader is a form of fennel (Foeniculum vulgare). It is unknown, however, if the invasive fennel plant is related to the varieties used in horticulture. Cal-HIP members investigated the commercial production of fennel seed (a culinary spice) and fennel bulb (for eating) and found that these crops are not the source of the invasions: plants grown for seed are raised in isolated plots to guarantee purity, and all of the seeds are harvested before they can disperse. The plants grown for the bulb are harvested before they have a chance to set seed! Current research is using taxonomy to try to identify the existence or absence of a relationship between horticultural varieties and the wildland invasive plant.
Cal-HIP also has identified the need to investigate the distribution of certain wildland invaders like Washington palm (Washingtonia robusta) and Brazilian peppertree (Schinus terebinthifolia) in Southern California, and English holly (Ilex aquifolium) in the northern part of the state. Licorice plant (Helichrysum petiolare) will require mapping of the invasive populations and sampling to assess the existence or absence of a connection to horticultural varieties. Pennyroyal (Mentha pulegium), a medicinal herb, is not widely available in the horticultural industry – but since pennyroyal is invading vernal pools in parts of the state, Cal-HIP will investigate the potential connection between the two and find practical ways we can prevent future introductions. There is current research being done on edible fig (Ficus carica) to uncover which cultivars are found in invasive populations. It is hoped that some cultivars will not be found contributing to the problem, or that a sterile variety can be produced, so that we can continue to enjoy edible fig plants.
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.
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