It's a little trickier than most broad leaved weeds but I still wouldn't rank it as the worst. Not at all. In a lawn: the best is something containing triclopyr: there are "homeowner" formulations out there, in the big box stores, that are a little weak and use the amine. I'm pretty sure the current version of "Weed B Gone" is tc amine. At the very least add a few drops of dishwashing detergent, because I think they skimp on the surfactant, and use the strongest dilution recommended. It is best to do it in the fall, but it might have seeded at that point, second best is spring, summer is the worst because I think it goes semi-dormant. I personally used a triclopyr ester in the fall and got complete kill of huge patches. A "3 way" formulation works too, albeit not quite as well as triclopyr so I wouldn't bother. Crossbow would work but again that's a "professional" product and I wouldn't recommend it unless you can handle using those. Just in a bed? Use a strong dilution of glyphosate, again, with enough surfactant to completely wet the leaves. Trust me, if applied correctly, it will die. Maybe not until 10 days later, though. When you're done with the glyphosate, please don't drink it or use it as a cocktail mixer. It might 'cause cancer': just as dairy (even organic), red meat, alcohol, or refined sugar might. I just spot treated some tiny areas of it with triclopyr ester, but this late in the season you have to be very careful about the vapors hitting nearby plants if you dealing with it near an ornamental bed. I once got into a bit a trouble with a huge area-wide application of tc ester to kill charlie and violets: we had an inversion that night, totally still air which is very unusual here, and fog formation. The vapor hung in the air and somewhat burnt the foliage of a Cedrus 'Shalimar' and a couple other ornamentals. They survived but it was a learning experience. Nothing would have happened if there had been some wind that night. I share the story to say: be careful with ester formulations. But, violets and charlie are completely gone from the main part of my lawn. (the spot treatment I mentioned was for a side area of grass, near ornamental beds, where I didn't want to use my ATV sprayer)

Minibim, you are correct that many exotic plants are fine for wildlife in your yard. I agree with that, which is why I added the caveat above about whether or not you can contain the plant in question. Butterflies love many plants that we would not want to see taking over our natural areas, for instance. The point I'm trying to make is that when these plants escape into the wild and begin to eliminate native plants, in the wild, they become a problem. Our native plants are home to hundreds of animal, avian, and insect species, and we can't lose large areas of those plants without suffering damage to our native wildlife. I don't care HOW widely something spreads in a garden. That's up to the person gardening. What I worry about is anything planted in a yard that can easily become an invasive plant in the wild. If you can contain your wedelia and you like it, I don't see anything wrong with that. Species like Chinese tallow and golden raintrees can NOT be contained, and those are deadly to our wild areas. Felix, your wedelia is contained by the nature of your property. You live in an area that was once pastureland, and you have a huge border around you. I don't think your wedelia is going anywhere else. (Unless it spreads by seed, which I suspect is not really the problem.) Minibim, if you have yours contained and controlled, I don't see it as a problem, either. And I agree that our official list of "invasive" species should contain more info on how and why they are a problem. I'm guessing my long absence from here has gotten me out of the practice of expressing myself things clearly. Sorry about that. Marcia

Australian tree ferns: Plant possible invasive concern by Carolyn Lucas West Hawaii Today clucas@westhawaiitoday.com Wednesday, March 18, 2009 9:07 AM HST Though prized for its distinctive looks and rapid growth, the Australian tree fern is becoming an increasingly common and alarming fixture in Kona neighborhoods, according to a recent islandwide survey by the Big Island Invasive Species Committee's early detection crew. On the underside of its triangular fronds with lacy blades are millions of spores, which breezes -- as well as feral ungulates -- carry far and wide. This tree fern (Spahaeropteris or Cyathea cooperi) is already displacing native forests on Kauai, Maui and Oahu. Watersheds are also being choked. Such propagation is just beginning on the Big Island, said Page Else, spokeswoman for the Big Island Invasive Species Committee. "The tree fern crowds out our native hapuu, the mother of the forest. The soft fibers of the hapuu nurture young native seedlings of native plants like ohia and olapa," she said. "The Australian tree fern has a harder, scaled trunk which doesn't make a good home for seedlings. Consequently, the foreign plant can take over in our forests, changing the forest structure, lessening the number of native plants and decreasing the ability to capture water and provide good water quality in watersheds." It's no wonder that the Australian tree fern appears on a list of the most invasive plants in Hawaii, prepared by the Hawaii State Alien Species Coordinator and the Department of Land and Natural Resources' Division of Forestry and Wildlife. Officials urged people to not cultivate any of the listed species anywhere in Hawaii. The Big Island Invasive Species Committee recently issued an Australian tree fern alert, spreading awareness about the weed and hoping that residents will help prevent its spread. People should report tree ferns by calling the state pest hotline at 643-7378. Those who have purchased the popular ornamental but suffered buyer's remorse and now want to remove it can either snip the bud or cut down the tree fern and treat it with herbicide. "They should be aware that their tax dollars will be put to work combating the rapid growth of this plant in public watersheds as seeds spread out of their yard into other locations," Else said. Two years ago, the Kauai Watershed Alliance contracted the Nature Conservancy to coordinate a response to the invasive tree fern. Crews on foot are sent into valley uplands to remove plants at a cost of $365 per acre. Helicopters with herbicides spray in more remote, dangerous areas. The aerial spraying costs $560 per acre, Else said. James Leary, invasive weed specialist at University of Hawaii at Manoa College of Tropical College Agriculture and Human Resources, has been experimenting with an innovative way to apply herbicide selectively to Australian tree ferns by using paintball guns with a special pesticide formulation. While people may be fond of the tree ferns, a wide variety of noninvasive alternatives, including the native hapuu, can be used as ornamentals. Because each yard is different, residents can visit a nursery and talk to an expert to find the best fit. Many nurseries -- including 15 on the Big Island -- agreed not to sell the tree fern after learning its potentially detrimental impact. For more information, call the Big Island Invasive Species Committee at 933-3345.

I'm gardening in an area of California called Marin County, which is north of the Golden Gate bridge and adjacent to the wine growing region of Napa and Sonoma Valley. We have 2 huge infestation problems that effects our agricultural economics. Because our 'infestation' problem(s) are affecting the economics of the region we have been assisted by the state legislators with funds for research, education and hopefully a control or remedy soon. Sudden Oak Death syndrome - SOD - is killing off our majestic old oaks at an alarming rate and is is now found to be in our redwoods as well as all the host plants such as Rhodo's, madrones, ect.. The lumber industry has been very active in lobbying for help and the UC ag system has been working full time on trying to find a solution. The wine industry is another extremely powerful lobby and they have done more than any other organized industry to get their message out about the Glassy Wing Sharp Shooter insect. Now when I bring in an order of plants that originates from a county out of my region I must call the ag inspector several days before my plants arrive in order to set up an inspection date. Once the plants are dropped off on the site they cannot be moved until they are inspected. So making sure that you set up your appointment well in advance is required so that you don't hold up your crew waiting for an inspector to arrive before you can place or plant your plants. We also have all the other transient insects, fungal diseases and soil born diseases to deal with. At the moment I am going head to head with a boxwood blight that is killing off my potager hedge and have spider mites on my passifloras. I think education is key when dealing with clients as well as keeping ourselves updated about IPM's and other organic measures one can take to combat infestations. Hort Oil, Neem and BT is my friend. I don't and won't use any toxic chemicals . I used to be a chemical queen in my early 20's and all thru hort school, but after a series of health scares I won't touch them anymore. If a client want to go into chemical warfare, then they can drop the bomb, but most here in my 'hood are pretty health conscience and fortunately prefer to use organic measures.