Marie Jasieniuk is a professor with the Dept. of Plant Sciences at UC Davis.
A major pathway of introduction of non-native invasive plants into new geographical areas is the global horticultural trade in ornamental plants. Even though only a small percentage of ornamental species escape cultivation and become invasive, those that do can have major negative impacts. In California, more than half of the most invasive plants damaging the state's wildlands and natural areas are derived from horticultural ornamentals. PlantRight™ (https://plantright.org/) is a collaborative effort including nursery professionals, conservation and environmental groups, invasive plant managers, scientists, and government agencies working together to prevent ornamental plant invasions.
Using the PRE tool, individuals with botanical knowledge and experience with literature reviews and research conduct risk evaluations for a particular species and specific region. Twenty questions need to be answered including questions on the species' invasion history in areas with similar climates worldwide and locally, impacts on native plants and animals, reproductive strategies, and dispersal. Each question is yes/no with a weighted score that the PRE tool automatically sums over all questions to produce a final PRE score (out of 25). Species with a final PRE score > 15 are viewed as having a high potential risk of becoming invasive; those with scores < 13 as having low potential risk and those with scores of 13-15 as moderate potential risk. Once evaluations are completed for a species in a region, a set of three plant experts, one each from the fields of conservation, horticulture, and academia, review the invasion risk evaluations for thoroughness and quality from the perspective of the three disciplines. If information is lacking, more must be sought and added to an evaluation, which is then re-reviewed. Once accepted by the reviewers, the invasion risk information for an ornamental species becomes available to nursery professionals as well as to consumers (https://plantright.org/about-invasive-plants/plant-list/). In addition, consumers are informed of non-invasive ornamental alternatives.
PlantRight is a model of effective problem-solving arising from the collaborative effort of nursery (business), environmental, management, and scientific professionals.
- Author: Janet Hartin
What do ice cream, potato chips, Scotch and Spanish Broom, and Tree of Heaven have in common? While they're all tempting to indulge in, less is more. In fact, plants such as Scotch, Spanish Broom, Tree of Heaven, Pampas Grass, Green Fountain Grass, and dozens of plants are all considered invasive plants in California. Simply put, they should not be planted. There are some great alternative plants that are better choices listed at the end of this blog.
Truth be told, I admit to falling madly in love with the Spanish Broom (Spartium junceum) shrubs adorning Highway 18 on my drive from San Bernardino to Lake Arrowhead in early spring 1984 right after my job interview for my current position. Being a “wet behind the ears” recently hatched graduate student from the Midwest I was truly in awe of their lovely yellow blooms and vowed to plant one if I got the chance to move to California. Fortunately, I found out very soon that, while the plantings were made on purpose, they were a mistake and needed to be removed due to their invasive nature.
While they were ‘recruited' from Europe and had what seemed like a perfect resumé (fast growth, lovely yellow flowers, adaptability to poor infertile soil and disease and insect-resistance), they didn't play well with others, a fatal flaw. In California, they were aggressive and crowded out native plantings. Fires only exacerbated the situation. After the 2003 burns, the Spanish Broom populations exploded, obliterating any remaining natives and taking an even larger area hostage. In summer 2010, the San Bernardino National Forest removed the plants in a costly but necessary $500,000 project under a partnership with the American Recovery and Reinvestment Act. Constant monitoring continues in the San Bernardino Mountains and other areas of the state to prevent its reestablishment which is challenging due to its ability to quickly resprout, seed longevity, and effective dispersal. It has definitely earned its ‘noxious weed' label!
This is just one example of the problems posed by invasive plants. In effect, they grow too well! They outcompete desirable plants in our gardens, lawns, and other urban and natural areas for water, nutrients, and space. They also shade sun-requiring plants. Threatened and endangered plant species and other California native plants are particularly vulnerable to their encroachment. (In most cases, invasive plants are non-native species.) Interestingly, our beloved state flower, the California poppy, is an invasive plant in New Zealand, Hawaii and other locations outside of California.
As urban gardeners, we can all greatly reduce the impact of the encroachment of invasive plants in our urban environments. Please don't plant invasive sane remove plantings on your property to stop their spread. Below are some great resources to learn more about invasive plants and find viable replacements:
California Invasive Plant Council: https://www.cal-ipc.org/
Don't Plant a Pest: https://www.cal-ipc.org/solutions/prevention/landscaping/dpp/
Invasive Plants of Southern California:https://www.cal-ipc.org/solutions/prevention/landscaping/dpp/?region=socal
From the Topics in the Subtropics blog :: March 4, 2020
* * * * * *
So I've gotten a few calls lately about this vine with a big green pod that is growing in lemon trees. What is done with it and how do you get rid of it?
Araujia sericifera, cruel vine, moth plant, bladderflower is an escaped ornamental that has become an invasive weed in California. Yes, a pretty vine brought into the garden – “poor man's stephanotis” - and it's gotten out of the garden into southern California. It's in the hills, in abandoned orchards, on backyard fences and when it gets into a lemon tree, it takes some effort to remove it before the seeds spread to other trees and beyond.
Bladderflower is a perennial vine that is very vigorous where it gets summer water. It is a common weed in citrus groves, where it would enshroud & smother entire trees if not controlled. Stems are tough and ropy, leaves thick and slightly spongy. Sap is milky white, moderately poisonous and causes skin irritation. It flowers Aug-Oct and the seed pods are obvious later in the fall. The flowers have a pleasant fragrance like jasmine. The reason for gardeners planting it. Plus it grows fast in our environment.
So the vine is entrained in the tree canopy so you can't spray an herbicide. To get rid of it, it's important to get down to the base of the tree and cut it out at ground level, removing as much of the root as possible. It still can regenerate, so it will be necessary to monitor the site, removing new growth as it might happen. Be sure to use hand protection because many people are allergic to the sap. Just cutting the vine at its base is sufficient to kill it. Removing the rest of the vine is necessary if there are pods, in order to prevent them going to seed.
The upside of the plant aside from the fragrant flowers is that it is an alternative food source for monarch butterfly caterpillars.
Calfflora shows cruel vine spread mostly along the coast south of San Luis Obispo, but it has the potential to spread thoguhout much of California. Currently, in the US, it is only found in California and Georgia. It is in New Zealand and Australia.
USDA Description of Plant as attachment below:
Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of the Contra Costa County
MGCC HD Client's Request: I live in West County along the Bay. There is a very large patch of “bamboo” that I would like to identify so I can take the appropriate measure to eradicate it.
I'm calling it a “bamboo” until I know what it actually is. I have heard that it really isn't a bamboo and that it is invasive. It grows 12'-18' tall. The stalks are up to 1.25" diameter. It is so dense and there are a lot of aphids. It is a rhizome bamboo, not the clumping type. It has taken over and is spreading like crazy to the other side of our house.
Below are photos. One photo shows the big patch to the left of our house. The other 2 are close up images.
MGCC HD Response: Thank you for contacting the UC Master Gardener Program with your questions about the large patch of “bamboo” next to your home. Your guess that it is not actually bamboo is correct, and from the very clear and helpful photos you sent we can identify it as the Giant Reed, Arundo donax. Actually, this plant is easily confused with bamboo as they look quite alike, and can spread and grow large. Bamboo leaves are attached to the stem, or culm by a short stalk, but your photos show a yellowish collar around the base of the leaf, which is characteristic of the reed. (see photo here https://www.sfei.org/nis/giantreed.html )
It will be quite an undertaking to eradicate this weed, and you will need some good friends to help!
We have some UC information on dealing with woody weeds, but the size of your infestation seems a little beyond this advice http://ipm.ucanr.edu/PMG/PESTNOTES/pn74142.html
We consulted with a biologist from the Contra Costa Agricultural Commissioner's office, and he was not aware of any programs to assist homeowners with the giant reed. You could begin to mechanically remove the plant material, but there will be re-growth from the stumps, and these would need to be treated with herbicide (see links for details) If you are close to water you would need to use a product approved for such areas.
We wish you all the best with this endeavor, please let us know how it turns out.
Help Desk of the UC Master Gardener Program of Contra Costa County (SMW)
HOrT COCO Editor's Comment: Unfortunately, this editor is well aware of Giant Reed. It is almost everywhere in the County. When moving into my bare dirt subdivision house in mid-County 50 years ago, I was scavenging any “free” plants I could find to start my garden. I “found” Giant Reed on a nearby empty lot that I thought was bamboo, dug some up and planted it on my initial hillside garden attempts. Several years later I found that it was Giant Reed from knowledge gained at my job when I observed big projects clearing Giant Reed from channels and creeks. Luckily for me, my hillside wasn't that fertile and I hadn't really watered it, so I started to remove it… still took three years of frequent and hard work to eradicate it. From the pictures submitted above, eradication will be a BIG job for this client.
Note: UC Master Gardeners Program of Contra Costa's Help Desk is available almost year-round to answer your gardening questions. Except for a few holidays (e.g., last 2 weeks December), we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 2380 Bisso Lane, Concord, CA 94520. We can also be reached via telephone: (925) 608-6683, email: email@example.com, or on the web at http://ccmg.ucanr.edu/Ask_Us/. MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (//ucanr.edu/blogs/CCMGBlog/)
Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Response from the UC MGCC Help Desk: Yes, the Cotoneaster lacteus is invasive. For root sprouting species, it is very difficult to find and mechanically remove all roots. Root systems generally spread beyond the width of the leaf area by 3 - 6 inches or more. So if your desirable plants are within 1 foot of the Cotoneaster, their root systems will likely overlap, making complete removal of roots difficult.
The UC Davis guidance mentions 2 herbicides that are effective for chemical control of Cotoneaster and available in California.
Glyphosate concentrate (e.g., Roundup™ for stumps) used as a cut stump treatment is a good option for management of woody weedy invaders. To use, you would leave some of the stems protruding above ground and carefully apply the product to the cut surfaces immediately after making the cuts. A small paint brush is often used for this typr of treatment. Fall is the best time for this type of treatment since the product will be carried down into the roots. If it is not 100% effective the first time, you can re-treat the few sprouts that might come up. Glyphosate degrades quickly, does not spread to other plants in the soil, and has low toxicity to humans and other animals. Glyphosate is usually available in smaller sized containers (eg. 8 ounces). There would not be concerns about replanting if you use this method.
The triclopyr herbicide, sold as Garlon 4 ultra™, has some serious downsides, but is another option. I found a 1 quart size through a Google search of "Garlon 4 ultra" under the "shopping" tab. This herbicide is also best applied as a cut stump treatment and fall is the best time of year to do this. The serious downsides to this chemical are that it can easily spread into water sources via runoff, has a 30 day half-life (i.e. is persistent), and is very toxic to fish and other aquatic species. This product is also volatile and should only be used during cool weather when there is no wind.
If you choose to use chemical control, we recommend that you try the glyphosate concentrate first, and only resort to triclopyr if the glyphosate is not effective after 2 or more applications.
Precautions should always be taken when using pesticides, as detailed here: http://ipm.ucanr.edu/PMG/PESTNOTES/warning.html.
I hope that this information is helpful. Please do not hesitate to contact us again if you need further assistance.
Note: The Help Desk of the UC Master Gardener Program of Contra Costa County (JL)Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: firstname.lastname@example.org, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (http://ucanr.edu/blogs/CCMGBlog/).