Posts Tagged: invasive weeds
Some tips on grazing for invasive plant control
The owner of the livestock (called the grazier) usually has a different goal for the animals then you do. The grazier wants the animals to fatten up for the market. You want them to eat weeds. If the weeds are what the animals want to eat and they are nutritious, then your goals are compatible. It is more often the case that the weeds are not desirable and the animals will try to eat everything else instead.
The grazier wants to turn the animals out to graze when she/he arrives at your site. You want the animals to stay in a penned area for 2-4 days eating hay and voiding all of the weed seed from their last site. You also want the pen in case of rain, rather than allowing the animals to wander around in the mud and trample small plants.
Livestock do not often eradicate weeds; they just remove above ground stems and foliage. The San Diego Weed Management Area tried goats for control of perennial pepperweed (Lepidium latifolium) a few years ago. The grazier promised that the goats would eradicate the weed if they were allowed to graze it twice in the summer for two weeks each time. They rented the goats to the WMA for $300/acre. The goats removed about ½ of the stems and foliage and a year later it looked like it had never been grazed.
Graziers are used to driving hard bargains, so make sure you know what you want and are ready to insist on it.
Don't get me wrong, livestock can be very effective and useful in large-scale weed management if they are suitable consumers of the target weed(s) and they are managed properly. I collaborated with several UC scientists to study sheep grazing as a weed control practice in newly planted alfalfa in the low desert. The sheep were very successful, as good as the herbicide alternative. Citations for three of our papers are on this website page (near the bottom). This short blog only presents some of the issues, especially those I have personal experience with. After spending eight years studying sheep grazing, I like to say that I know far more about sheep than I ever wanted to.
You just KNOW that some plants are weeds. Their common names give it away. They sound awful. Giant hogweed (Heracleum mantegazzianum). Ripgut brome (Bromus diandrus). Devil's claw (Proboscidea lutea). Smellmelon (Cucumis melo). Itchgrass (Rottboellia cochinchinensis). Dog-strangling vine (Cyanthum rossicum).
Others...others seem more benign. Even sweet. For Valentine's day I present to you nine weedy plants with lovely names. Enjoy...
1. Tree-of-Heaven (Ailanthus altissima). How celestial. How divine. How invasive. Tree-of-heaven is a deciduous tree, native to China, in the Simaroubaceae. It has been used, extensively, as a street tree; in fact it is the subject of A Tree Grows in Brooklyn by Betty Smith. But it suckers. A lot. And it stinks. A lot. And it spreads, rapidly, by seeds (lots and lots of seeds!) and root-sprouts. Some urban areas have even renamed it 'Tree-of-Hell'.
2. Baby's breath (Gysophila paniculata). Baby's breath?!?!? Baby's breath?!?!? That delicate plant in the Pink family that is beloved by florists? You would have to work hard to make up a sweeter sounding name for a pest! Like 'Fuzzy kitten herb' or 'Baby giraffe weed'. Or 'Mouse ear chickweed' (wait a minute, that last one is real...). But baby's breath can become invasive in certain habitats, such as Sleeping Bear Dunes in Michigan, where it escaped from gardens.
3. Amaranthus spp. The origin of the genus is derived from the Greek words marantos (unfading) and anthos (flower). Unfading flower. A perfect metaphor for love. Well, I've got two words of my own for you: PALMER AMARANTH. Enough said. (To be fair, many Amaranths are used worldwide as food sources, either leaves or seeds...but my animosity isn't directed at them.)
4. Love-apple (Solanum capsicoides). Sounds delicious, right? If you are talking about a tomato (Lycopersicon lycopersicum), sure. If you are talking about red soda apple (i.e. love-apple, devil's apple and cockroach berry), not so much. The fruits are toxic and have been used in many countries for rodent and insect control.
5. Multiflora rose (Rosa multiflora). A 'rose with many flowers', how can that be bad? HA! The intentions were good when this species was being promoted in the 19th and 20th centuries (ornamental shrub, erosion control, living livestock fence, wild-life food source), but things have gone terribly wrong since then. This shrub forms dense stands that displace native vegetation.
6. Love leaves (Arctium minus). It sounds like you could brew up a nice aphrodisiac from this species. Although parts of the plant are said to be edible, love leaves, better known as common or lesser burdock, is also listed as being toxic in many weed guides. However, burdock doesn't make this list because of its questionable medicinal or culinary virtues, but rather for its seed. The tiny hooks on the seeds of this plant were the inspiration for velcro. Try pulling them out of the fur of a long-haired dog...
7. Heart's ease (Polygonum persicaria). Better know as smartweed or ladysthumb. This weed can grow everywhere, it seems. Seriously. It is even found in Greenland.
8. Love vine (Convolvulus arvensis). Love may keep us together, but you don't want to be in a relationship with this plant, which is better known as field bindweed. This perennial species is listed as one of the most noxious weeds in the WORLD. It has roots that can grow to depths of >10', it reproduces by seed and rhizomes, infrequent tillage just makes it mad, and repeated applications of herbicides are needed to suppress it. This plant also goes by the name possession vine...and you're nobody's property.
9. Bouquet-violet (Lythrum salicaria). People love getting flowers on Valentine's day, right? Maybe you shouldn't send this 'bouquet', though, which you probably know better as purple loosestrife. This plant was introduced, intentionally, to North America as an medicinal herb, but it has since escaped from our gardens and become naturalized. Large infestations can alter water flow in streams and rivers, reduce native plant species diversity and negatively impact macrofauna, such as amphibians and waterfowl, that rely on wetlands for food and shelter.
My title is Regional Advisor – Invasive Plants, but I really think of myself as a Weed Scientist (which sometimes gets an interesting response from some people; those that likely have a smoking habit).
Weed is a simple word; everyone knows the word and has an idea of what it is referring to, right? It’s a plant that someone doesn’t like for some reason. Or perhaps it is a plant existing somewhere it doesn’t belong. The definition that the Weed Science Society of America (yes there really is a Weed Science Society of America, and no they do not do research on “WEED”) uses is, “any plant that is objectionable or interferes with the activities or welfare of man or the environment.” (The italicized part of the definition was added on in recent years to make all of us invasive plant folks happy.)
All of these ways of defining weeds include a human connection; we don’t like them, they are in an unwanted place, they interfere with our interests. That means that a plant is only a weed when we say it is. Plants that are weedy often have biological traits, like rapid germination, prolific seed production, or airborne seed, that enhance their weediness, but these traits do not create a biological definition of a weed. (For more on this subject and an outstanding attempt to define weed, see Radosevich, S.R., J.S. Holt, and C.M. Ghersa. 2007. Ecology of weeds and invasive Plants. Wiley Interscience, chapter 1.)
To me this is the important value of the term Weed; it reminds us that we are responsible for weeds and make decisions regarding what to do about them, even if it means doing nothing, which is too often the case. Even when a plant is naturalized, (naturalized has a benign feel, doesn’t it?) it just means that that particular weed has settled in well in its new home. An excellent paper on this subject and the proper use of invasive plant terminology (Richardson, et al. 2000. Naturalization and invasion of alien plants: concepts and definitions. Diversity and Distributions 6(2):93-107.) states that “between 50 and 80% of invasive plan
t species can be classified as pests or weeds, depending on actual impacts and human perceptions”. And when you consider weeds like wild oats (Avena fatua) or black mustard (Brassica nigra) that have been in California for over 250 years and are ubiquitous, the adjective “invasive” does not seem to be appropriate any longer, how about “invaded”. By the way, the California poppy below, our official state flower, is a serious agricultural weed in Chile.
So if I tend to use weed instead of invasive plant, I hope I have justified my rationale. On the other hand, when I meet someone these days and they ask what I do, they seem to understand when I say I do research and education on invasive plants. When I say I am a Weed Scientist they often look at me in an odd way; so I’m probably all wet anyway.
So I think that I can accept my hypothesis; kill the weedy annuals thoroughly for several years, do not let any of them produce seed and the natives will respond marvelously. My reward is seeing natives thrive, illustrated by the photos all taken at these sites over the past 7 years, including the solid cover of purple needlegrass below.
Original source: Invasive Plants in Southern California blog
Carl Bell, University of California Cooperative Extension Regional Advisor on Invasive Plants, created a new blog on invasive plants in southern California. Here's a look at the blog: