California Invasive Species Week is June 3-11. This is the perfect time to raise awareness about the impact of invasive plants on our natural ecosystems and the importance of making informed plant choices. Invasive species can have detrimental effects on local flora and fauna, often outcompeting other plants for resources and disrupting local ecosystems.
By selecting plants that are well-suited to your environment and not invasive, you can make a positive contribution to preserving California's diverse landscapes. Many invasive plants can be aesthetically pleasing and low-maintenance, making them a popular choice for gardeners. However, invasive plants can spread rapidly, taking over natural habitats and causing significant environmental damage. Invasive species often have few natural predators, enabling them to grow uncontrollably and outcompete other plants for resources like water, sunlight, and nutrients. This can lead to the loss of biodiversity, reduced habitat quality for wildlife, and increased risk of erosion and wildfires.
Examples of Invasive Plants in California:
1. Periwinkle (Vinca major)-This evergreen groundcover is a popular species because of its beautiful purple blooms. Periwinkleforms dense mats that can smother native plants and alter soil chemistry. Instead of periwinkle, try planting native groundcovers like California lilac (Ceanothus spp.) or hummingbird sage (Salvia spathacea).
2. Fountain grass (Pennisetum setaceum)-This ornamental grass is highly adaptable and has invaded many natural habitats, including grasslands and coastal sage scrub. Instead, opt for native grasses like purple needlegrass (Stipa pulchra) or deergrass (Muhlenbergia rigens) or the smaller version (Muhlenbergia dubia).
3. Pampas grass (Cortaderia selloana)-A tall, clumping grass with feathery blooms that can quickly dominate landscapes and outcompete native species. Consider planting native ornamental grasses such as blue grama grass (Bouteloua gracilis) or switchgrass (Panicum virgatum) as alternatives to pampas grass.
4. Tree of heaven (Ailanthus altissima)-This fast-growing tree can release chemicals that inhibit the growth of other plants and can sprout vigorously from root fragments. Plant California native trees like sycamore (Platanus racemosa) or western redbud (Cercis occidentalis) instead of the invasive tree of heaven.
Celebrate Invasive Species Week!
organization dedicated to protecting California's wildlands from invasive plants through
research, restoration, and education.
•California Native Plant Society (CNPS)-https://www.cnps.org/-CNPS is a non-profit
organization that promotes the understanding and appreciation of California's native plants and
preserves them in their natural habitat.
•PlantRight-https://plantright.org/-PlantRight works with California's nursey industry to keep
invasive plants out of our landscapes and promotes the sale of non-invasive alternatives.
Drive anywhere along the coast this time of year and you will see huge stands of large 6'-10' tall grasses with dramatic pink plumes blowing in the wind like flags. What you are looking at is Jubata Grass or Pampas grass and it has become a real problem in our coastal habitat.
In fact, this well adapted plant will come up just about any place where there is little competition and will quickly establish on bare soil. It forms massive clumps along roadsides, steep cliffs, riverbanks, and open areas that have been disturbed by human activities or natural disturbances. You will notice it in town around parking lots and in that bare spot of dirt near the sidewalk or the edge of the garden. With the ability to grow in many conditions Jubata grass can quickly spread and become out of control.
Introduced to California in 1848 by nursery operators, Pampas Grass (Cortaderia selloana) became a popular specimen plant with fluffy white plumes used for decorating. It is not the species causing all the problems. Several decades ago another species, Cortaderia jubata, was introduced and has since become a primary invasive weed in coastal areas of the West. It is generally distinguished by a pinkish flower plume, but otherwise difficult to tell apart from C. selloana. Because it spreads quickly and is miserably impenetrable, it was once used by logging companies to keep deer from eating reforested areas. In the 1960's, Georgia Pacific had to abandon 1,100 acres in Humboldt County where jubata grass had taken over as there was no economical way to control it. At that time 7,000 additional acres were severely infested. Now recognized as incredibly invasive, lawmakers, educators, nurseries, restoration groups and homeowners are uniting in the fight to eradicate the pest.
Dramatic and majestic, Jubata Grass can be hard to dislike. Attractive feathery pinkish plumes appear on top of tall stalks well above a fountain of graceful leaves from July through September. However, we need to educate ourselves and others about the downside of this dramatic invasive plant. Just think… each plant can produce millions of seeds annually that can travel several miles. Once established, the vigorously growing jubata grass pushes out other vegetation and animals already living there. It takes over, clogging waterways and wetlands and causing environmental chaos. When dry, it can be a serious fire hazard. The sharply serrated leaf blades can cause physical harm to animals and humans. They are highly undesirable as food or shelter to birds and other wildlife.
So, how do we control it? We can begin by becoming aware of the problem. Next, we can work to remove any plants that we can. And, we can reduce the “seed bank” by removing flower plumes. In a recent hour spent along the roadside, I bagged over 150 seed plumes, each containing thousands of seed that will not have a change to germinate. Small plants can be pulled quite easily, so carry a pair of work gloves on your next hike.
Plume/Seed head removal: If removing the whole plant seems daunting, consider removing the flower stalks as they emerge to prevent seed dispersal. This will need to be done early and repeatedly throughout the blooming season. Although the flower plumes are striking, DO NOT pick them for decorations or floral arrangements.The flowing flag of the seed head should be cut and burned to prevent seed dispersal. Alternatively, cut and bag all seed heads as soon as they appear and send the bag to the landfill. Avoid leaving them on the ground or composting them.
Research has shown that burning and grazing do not provide long term control and pampas plants quickly resprout. Biological controls have not been investigated. Glyphosate is the most effective herbicide to reach the deep roots of Jubata and Pampas Grass. Follow manufactures instructions carefully. Protect nearby desirable plants from herbicide spray drift and apply when insects are not active. Do not overspray and avoid runoff into waterways. Please see link below for more information regarding Glyphosate.
UC IPM Glyphosate Link
University of California Weed Research and Information Center Leaflet 99-1 Link
California Invasive Plant Council Report Link
California Invasive Plant Council Cortaderia jubata plant profile Link
Pacific Horticulture Article by John Madison - Pampas Grasses: One a Weed and One a Garden Queen Link
Images - permissions granted
Pampas Grass in Landscape - photo by Sherida Phibbs, UCCE Master Gardener Coordinator
Coastal hillsides covered in invasive Jubata grass - photo by Annie Sciotte, UCCE Master Gardener
Making this trail unusable - photo by Annie Sciotte, UCCE Master Gardener
- Author: Gayle Nelson
By Susanne von Rosenberg, UC Master Gardener of Napa County
If you live in an older home, you likely inherited some amount of old landscaping. Many of us have already tackled the grass, but what about the rest of the garden?
Many plants that were once landscape standbys have now proven to be undesirable for a variety of reasons. Unfortunately, many perennials became landscape standbys because they were hardy and vigorous. Some of the more common of these plants include juniper (highly flammable), Algerian and English ivy (invasive; can kill trees and destroy fences; provides habitat for rodents), broom (highly invasive and flammable) and Pampas grass (highly invasive and flammable).
Unfortunately, mulches will not kill these plants. Mulches can effectively control annual plants, but they do not work for perennial plants that can resprout from underground parts.
Three basic types of removal are appropriate for perennial plants: mechanical removal, biological control or chemical control. There are no biological controls for any of these plants because many people still consider them desirable.
Mechanical removal includes hand removal, mowing, burning and selective grazing. Use caution when mowing during the dry season because of fire danger, especially if your property is rural. Mowing later in the season could also spread seeds.
While mechanical removal is more environmentally friendly, using post-emergent herbicides can also be successful. Chemical control is most appropriate for controlling resprouts. Depending on what you intend to plant next, you may have to wait a year or two after using the chemicals. Always follow the label directions and wear proper safety gear.
As for digging up these unwelcome plants, do it now when the soil is moist and the roots are more easily removed. When the soil is dry and hard, digging often just breaks off the stems, leaving most of the plant material to resprout.
Burning is not recommended for resprouting plants as it increase the population of these plants. Never burn poison oak; the smoke is a serious health hazard.
Hand removal can be effective for juniper, Pampas grass and its close relative, jubatagrass. Cut down or pull out Pampas grass or jubatagrasss before it flowers to avoid spreading seeds. Be careful; Pampas grass has sharp edges. After you have removed the plant, dig out the rootball. Watch for reprouting from any root fragments. It may take several years to get rid of the Pampas grass completely.
To remove juniper, cut the bush at soil level. The main trunks are often thick enough that you need a chainsaw to cut them. You can watch to see If any sprouts emerge from the roots left in the soil, or you can remove the main part of the rootball to reduce the likelihood of resprouting.
If you are eager to remove the rootball, cut the main roots a foot or so from the trunk and then pry the stump out of the soil. Even if you remove the main stump, it's still a good idea to periodically check for resprouts. I have cut a juniper hedge back to the ground and had no problems with any resprouts, even though I immediately planted new plants between the stumps.
Of all the plants on this list, ivy will likely take the most effort to eradicate. It can spread by rooting from growing stems, seeds and even from cuttings left on the ground. Digging out the plants can be effective if you remove the roots and stems, including all the runners. Wear gloves when removing ivy. Many people react to dermatitis-causing chemicals in the plant. And be prepared to come back regularly to get rid of resprouts from roots that you missed.
If the unwanted plants aren't near any plants you want to keep, and the area you want to clear is large, goats can be effective. You will still need to look for resprouts in the grazed area.
Mowing the resprouts is not generally recommended as it can encourage regrowth. However, you may succeed if you mow during the dry season and follow up consistently to mow resprouts as well.
Broom is in a category by itself. Tackle it during the dry season. Lopping it back when the soil is moist can result in vigorous resprouting. Broom rapidly develops a large rootstock. Within a couple months of germination, plants typically have rootstocks large enough to recover from a single mowing. You will need to mow multiple times to eliminate broom.
You can also cut mature broom near the base. That will provide some control if you do it when plants are moisture stressed, such as in late summer or after a dry winter. Cutting it down when the soil is moist will cause vigorous resprouting.
Library Talk: Napa County Master Gardeners will present a talk on “Chasing Sun in Shaded Yards” on Thursday, December 2, from 7 p.m. to 8 p.m. via Zoom. Does your yard have a limited supply of sunny locations to grow vegetables? Learn about site selection and cultural requirements for the plants you want to grow. Register here to receive the Zoom link.
Workshop: Napa County Master Gardeners will lead a workshop on “The Art of Raising Succuluents” on Sunday, December 5, from 1 pm to 3 pm, at the Yountville Community Center, 6516 Washington Street, Yountville. Discover how to care for and design with these colorful, unthirsty plants in your garden or on your patio. Attendees will get plant starts to take home. Yountville residents: $16; Non-residents: $18. Free to Golden Ticket members.To register, visit Online registration or telephone the Parks & Recreation Department at 707-944-8712.
Got Garden Questions? Contact our Help Desk. The team is working remotely so please submit your questions through our diagnosis form, sending any photos to firstname.lastname@example.org or leave a detailed message at 707- 253-4143. A Master Gardener will get back to you by phone or email.
For more information visit http://napamg.ucanr.edu or find us on Facebook or Instagram, UC Master Gardeners of Napa County.
By Susanne von Rosenberg, UC Master Gardener of Napa County
One thing that Master Gardeners talk about a lot is putting the right plant in the right place. That means choosing plants adapted to the climate, to the soil in your garden and to the amount of sunlight and water they will receive.
One other consideration is whether the plants you're considering are invasive. Invasive plants threaten our wildlands, outcompete native plants and change the habitat so it is no longer suitable for some native species.
As a result, invasive plants pose a substantial threat to endangered species. Invasive plants can also threaten agricultural lands by crowding out crops and rangeland forage. Some are toxic to livestock or wildlife.
According to the California Invasive Plant Council, invasive weeds in pastures and farmland cost an estimated $33 billion per year nationwide. California alone spends an average of $82 million per year to deal with invasive plants.
Even in the suburbs, invasive plants can cause problems. Pampas grass and Scotch broom increase fire fuel loads; other invasive plants can clog creeks and increase the risk of floods. Still others consume large amounts of water that would otherwise have gone to other plants, waterways or drinking water.
Until I became a Master Gardener, it never occurred to me that garden centers and nurseries might sell problematic plants. Unfortunately, many of the plants causing problems in California were introduced through the horticultural trade. We need to educate ourselves to make sure that we don't plant a future problem.
I've been surprised how often a plant that seems otherwise ideal for my garden turns out to be potentially invasive. Gardening catalogs are another source of invasive plants. Some of these plants may be perfectly harmless in other parts of the country but invasive here.
How can you know if a plant you're considering might be invasive? First, you can check the Calflora website, which provides information on a large number of plants grown in California, including whether a given plant is considered invasive or has invasive potential.
You can also consult the California Invasive Plant Council website, which has an alphabetic list of problematic plants. That list includes plants commonly sold through the horticultural trade and assigns a rating of high, medium or low risk of invasiveness. In addition, IPC maintains a watch list of plants that aren't currently invasive in California but risk becoming so.
As you evaluate a plant for invasive potential, consider these questions:
Is the plant known to be invasive in other locations with a Mediterranean climate?
How readily does the plant reproduce? On average, how many seeds does it produce each year, and how easily does it germinate from seed? How long will it take until the plant is mature enough to set seed?
Does the plant spread vegetatively, such as via underground running stems (like running bamboo)? Can a new plant sprout from small pieces of root, like bindweed does?
How tough is the plant? Does it need regular water or special growing conditions to germinate?
Could the plant hybridize with existing plants?
Are other species of the same genus, or a related genus, invasive in a similar climate?
Would the plant increase the risk of fire? Is it highly flammable or does it soak up a lot of water and leave surrounding vegetation dry?
How easily can animals, wind or water spread the plant's seeds or vegetative matter?
How hard is the plant to remove or control?
Unfortunately, many of the qualities that make a plant desirable may also predispose it to being invasive. If it is adapted to our climate, easy to grow and requires little water, it meets some of the criteria of a potentially invasive plant.
Compared to well-behaved plants, invasives reproduce more readily, crowd out desirable plants and may be difficult to remove. So if a plant's description says that it “reseeds readily” or “spreads easily,” think twice. If it “grows rapidly” or is “adapted to adverse growing conditions,” do some follow-up research.
Unless you know the plant, it it's a good idea to spend a few minutes online to reassure yourself that the plant is well mannered. Don't rely on old information. Some plants have been designated invasive only recently, and new plants are added to the list regularly.
Food Growing Forum: Napa CountyMaster Gardeners will present a discussion of “Cane Berries” on Sunday, November 14, from 3 p.m. to 4 p.m., via Zoom. Register here to receive the Zoom link.
Got Garden Questions? Contact our Help Desk. The team is working remotely so please submit your questions through our diagnosis form, sending any photos to email@example.com or leave a detailed message at 707- 253-4143. A Master Gardener will get back to you by phone or email. For more information visit http://napamg.ucanr.edu or find us on Facebook or Instagram, UC Master Gardeners of Napa County.
- 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