- Author: Guy B Kyser
A recent request from the San Diego area has prompted the reposting of this blog by Guy Kyser, UC Davis Plant Sciences Specialist
http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=6296
A neighbor asked me to identify a robust perennial that keeps coming up in his garden. It had long, tropical-looking leaves and floppy racemes with small white flowers. This was a new one for me. Turned out it was common pokeweed (Phytolacca americana), a native of eastern North America. In the south some people eat it (poke salad), and a few southerners probably brought it west as a garden vegetable. But the whole plant is toxic if improperly prepared, so it's the fugu of weeds.
A couple of weeks later my daughter brought home a stalk of purple berries and asked if she could eat them. “No,” I said, “they contain numerous saponins and oxalates.” I began to wonder if there's more pokeweed around than I realized.
Then Gillies Robertson of Yolo RCD sent photos of a purple-berried plant found along a slough near Grimes. Common pokeweed again.
Pokeweed is in the Phytolaccaceae. This weed can grow to 10 feet tall. It dies back in winter then reemerges from the ground in spring, growing from a fat fleshy storage root. The leaves are large, 3 inches to a foot long and 1 to 5 inches wide, often with reddish stalks and lower veins. From August to October, pokeweed produces racemes of white flowers followed by reddish-purple berries. In its natural state, all parts of the plant, especially the root, are toxic to humans. Birds can eat the berries but sometimes act funny afterwards.
This plant can be found in most of the contiguous states. In drier regions, it prefers gardens and irrigated areas. Southerners with pokeweed experience suggest controlling it by digging up as much of the taproot as possible and/or by cutting off the stalks and painting the stubs with concentrated glyphosate (e.g. Roundup). Either way, treatments will probably have to be repeated until the plant's storage reserves are worn down. And it's a good idea to deal with pokeweed before it produces berries and seeds.
Since this is the first year I've seen it, and since I suddenly ran into it in three locations within a few weeks, I'm guessing that the common pokeweed population is expanding. This plant seems robust enough to cause some trouble if it becomes established in natural riparian areas.
- Author: Travis Bean
Invasive plants don't get much coverage in the news, especially at the state and national level. As I've argued previously, this lack of media attention is a problem when it comes to motivating the public and political players into proactively funding invasive plant management and mitigating impacts to human health, infrastructure, and natural resources. Admittedly, as a weed scientist, I'm biased on the issue.
However, sometimes there is a particular plant that is just so terrifying that it lends itself to coverage in a major news outlet, as was the case for this article about giant hogweed (Heracleum mantegazzianum) by Caitlin O'Kane on CBS news last month: "Giant hogweed, plant that causes blindness and third-degree burns, discovered in Virginia." As the headline suggests, this is a plant you should keep a safe distance from if you are unlucky enough to come across it. Just in case you're thinking that this is just sensationalism, there's a page on Snopes that confirms the assertions about giant hogweed's dangerous sap (and also confirms its place in popular culture). I won't provide a direct link here, but a simple Google search of "giant hogweed" turns up some images of what look like very painful giant hogweed injuries. The photograph below was taken by Gavin Edmondstone:
Giant hogweed is native to the Caucasus region and southwest Asia, and is presently found in Europe, Canada, the United States, Australia, and New Zealand, where it was likely introduced as an ornamental for its showy inflorescence. Apparently it was a well known nuisance in Britain, so much so that the band Genesis released the ominous song "Return of the Giant Hogweed" on their 1971 album Nursery Cryme:
"Turn and run
Nothing can stop them
Around every river and canal their power is growing..." (Google the song title for the complete lyrics- they are fantastic! And strangely factual...)
Here in the US, giant hogweed is mostly found in New England and the Pacific Northwest. As the article suggests, giant hogweed has expanded down the east coast and was recently discovered for the first time in Virginia. Over on the west coast, it has made it as far south as northwestern Oregon. Californians should be on the lookout however, as we do share some similar habitats with Oregon, particularly in the northern part of the state. California also has a native congener called "cowparsnip" (Heracleum maximum), suggesting that suitable habitats do exist across the state.
For those involved with management of this plant, a great resource with information on controlling giant hogweed can be found in DiTomaso et al. (2013) Weed Control in Natural Areas in the Western United States, as well as several state conservation webpages. Before embarking on control, be careful not to confuse with natives that may look similar- your local county Natural Resources Advisor can be of great help in correctly identifying invasive plants. And it should go without saying, but given the potential for painful injury, this is a plant you may want to enlist the help of professionals with if you have it on your property.
As the band Genesis proclaims:
We must destroy them
They infiltrate each city with their thick dark warning odor
They seem immune to all our herbicidal battering"
Now if we could just get some similar coverage in the press or popular culture for our less glamorous but equally terrifying invasive grasses...
- Author: Ben Faber
A recent blog by Farm Advisor Rachel Freeman Long in Yolo/Solano/Sacramento Counties alerted me to a weed that I thought was mainly a northern California plant.
http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=26918
But according to Calflora it's been found in Agoura Hills and Moorpark with two sightings in San Luis Obispo County.
http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=7048
Spiny buttercup (Ranunculus muricatus) is a non-native plant, that is fairly common, especially in wet areas such as meadows. We also find it in crops, including orchards, pastures, and cereal grain fields. It's both an annual and perennial plant that blooms from March to May, with seed pods that are large and prickly. Though it's pretty with the bright yellow flowers, don't be fooled, as it has a dark side, so should be controlled.
First, according to Dr. Birgit Puschner, UC Davis Vet Med Toxicologist, all buttercups contain ranunculin, though there are differences in species in terms of toxin levels. In pastures, because the plant is bitter, animals simply eat around it. But if ingesting the fresh plant, they can develop blisters. The toxin degrades in hay; thus, it's only a problem in grazing and fresh exposures.
Second, according to Dr. Gilbertson, UC Davis Plant Pathologist and Ozgur Batuman, former UCD Post Doc, buttercup is a significant host of tomato spotted wilt virus (TSWV). Other important weed hosts for TSWV include cheeseweed (Malva parviflora), sowthistle (Sonchus oleraceus), and prickly lettuce (Lactuca serriola). TSWV crop hosts include peppers, tomato, lettuce, and bell beans (fava).
The primary vector of TSWV is the western flower thrips, a tiny insect that feeds on the plant foliage. Immature thrips pick up this pathogen from infected plants and transmit it to healthy ones when they become adults and disperse to new host plants. TSWV is not transmitted via seed.
Symptoms of TSWV typically include necrotic spots, often with tip or leaf dieback that looks like drift from a contact broadleaf herbicide. However, there is a lot of variability in the symptoms of TSWV depending on the host that could be confused with other problems. As such, if you suspect TSWV in your crop, the best way to positively identify it is by using on-site tools to test for this disease, such as ImmunoStrip® tests. A good resource for TSWV in tomatoes is: Tomato spotted wilt disease in tomatoes.
Watch for spiny buttercup and control this weed to keep it from spreading. We need to keep our pastures safe and TSWV out of our crops.
/span>- Author: Ben Faber
Occasionally plants show up in our office for identification and no one in the office knows what it is. So it's sent off to to others who might know. This was the case of a perennial amaranth, also called goosefoot for some reason. The is Chenopodium californicum, also know as Blitum californicum.
Like other amaranths, it can be upright to 3 feet in height, or if mowed or grazed be more flattened or decumbent. It has a thick, fleshy stem that along with the leaves can be eaten. I guess pigs like it, because it's also called pigweed.
The leaves look sort of lettuce like, which gives it another name - Indian Lettuce.
The stem has also been used for making soap, which gives it another name of soaproot. Which is not to be confused with another soaproot, Chloragulum. Plant names can be confusing.
Chenopodium californicum, Blitum,goosefoot, pigweed, soaproot grows in the chaparral on slopes and in foothill woodlands, mainly along the coast.
Calflora: http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=1968
Plants for a Future: https://www.pfaf.org/USER/Plant.aspx?LatinName=Chenopodium+californicum
- Author: Ben Faber
Plant-out-of-place photo galleries:
http://wric.ucdavis.edu/photo_gallery/photo_gallery.htm
http://ipm.ucanr.edu/PMG/weeds_intro.html
Horseweed - Conyza canadensis
Herbicide treatment table for citrus:
http://ipm.ucanr.edu/PMG/r107700411.html
And if you are wondering what herbicide damage might look like on various plant species (this is heavily weighted to annuals and landscape plants):
http://herbicidesymptoms.ipm.ucanr.edu/index.cfm
Blueberry herbicide damage