Make sure you are trying to kill the right plant. Silly as it may sound; it is easy to misidentify something. You can end up pulling up the good guys, and carefully transplanting the bad. It has happened to most of us at one time or another. (Oops!) Fortunately, there are plenty of sites on the web, including this one, where you can compare your sample to known examples of the invasive plant. If you're still not sure, consult with your local Agricultural Extension Service, ask a knowledgeable friend, wait until it flowers, etc.

Know the enemy. Different approaches work for different plants. Many people have tried repeatedly to get rid of every conceivable "bad" plant and have recorded their experiences on the web. The information is there. You need to know how the plant spreads and what conditions it likes. For example, a plant that spreads by roots has to be treated differently than one that spreads only by seed; one that tolerates shade can be harder to kill than a full-sun plant.

Get ahead of the invasion. It is a lot easier to pull up a few small seedlings than to remove a forest. Many invasive plants are spread by bird droppings, so keep an eye out for unidentified plants underneath bird-roosting places, such as shade trees and fence posts. The early in spring you get started, the better. (And, unless you like stoop-labor, don't forget the mulch to keep the weeds down!)

Manage from the edge. Let's assume that the bad guys got going somehow and now you want to clean it up. Do NOT, do NOT start by diving into the middle of the patch, and trying to dig up the biggest one. As you'll see, this is a BIG mistake. The first step is the stop the spread by pushing back the newer and weaker growth at the border of the patch, inch by inch, if need be.

Stop the seeds. Even if you can't do anything else, if you can stop the plant from going to seed, you can limit the amount of damage that the plant does.

Use mechanical controls, not chemical warfare. "Mechanical" means pull the plant up, cut it down, or shade it out. However, if you're not careful, you can end up doing more harm than good even with mechanical means. Three need-to-know things are: seed bank, root-fragment regeneration, and proper disposal methods.

Seed bank: Many plants, including lots invasives and "weeds", have seeds that can live for years in the ground, waiting for the right conditions for germination. Some seeds need to only be exposed to light for seconds to start the biological process. Any time that the earth is disturbed by digging, cultivating, weeding, construction, etc, the seed bank is opened. This is why "disturbed earth" and "weeds" tend to be synonymous.

The seed bank is also why mulch is often a better weed-preventer than weeding; the mulch smoothers many of the weed seedlings without opening up the seed bank. If dig you must; it's important to come back weekly for a month or two to pull up any new seedlings. It's good if you can mulch the newly disturbed area (but don't ever pile on more than 3 inches of mulch or you'll kill the roots of the neighboring trees.)

Reports of seeds living up to 50 or 100 years in the earth are known. For most invasives, the majority of the problem are said to occur within 5 to 7 years after the seed-producing plants are removed. Even if the soil is not distributed, in the area around where the invasive was removed, you are likely to get seedlings every spring for at least a few years, so continuing vigilance is a must. Equally important are mulch and cover-planting of something correct for the area which can shade-out and crowd-out the unwanted seedlings.

Root regeneration: The way invasives get the label is by being very aggressive, hard-to-kill plants. So not only do many of them strew long-lived seeds all over the place, many of them can sprout from root fragments. So if you take your shovel and dig out a bunch of big guys but lots of little pieces of root remain the ground, not only have you opened up the seed bank, each of the little root pieces may regenerate. There was an army like this way back in ancient myths: slay one solider and a hundred new ones spring up.

Disposal: Once you have separated the unwanted plant from the land, what do you do with it? If the plant has mature seeds on it, anywhere the dead plant goes (e.g. your compost pile), so do the seeds. You can't even send the remains to the dump (assuming that it is legal to do so in your town), since birds will feast on the dump leavings and then spread the seeds. Likewise, many of these tough plants can re-root themselves if there's any contact with the soil.

The best method is to bag at least the seeds and roots in black plastic and leave the bag in direct sun for several months to sterilize. If you get the plant early enough in the year so it doesn't have seeds, bushes in particular, can be turned upside down in place so that the roots can not touch the soil again, even with the help of a strong wind. In a wild area, the up-ended bushes make good brush-pile habitat.

Hand pulling: Hand puling can almost always be used for isolated clumps, small plants, seedlings, and plants on the border of a large colony. Be aware that there can be continuing issues with the seed bank and root regeneration but with continued diligence, the balance is in your favor. Try to disturb the earth as little as possible, re-cover what you've disturbed, and try to get all the root fragments. Repeat at least monthly.

For large plants and bushes, there's a neat tool called a "weed wrench. This very cool device was invented by some even cooler self-described “tree people” who call themselves the “The New Tribe”. It gives a small person the leverage to take out a big shrub. You can get one at weedwrench.com.

Do not try to dig up or hand pull a major infestation without careful study and a plan to handle the long term aftermath. Otherwise, you may end up being the problem, rather than solving it. Major infestations are usually better treated by repeated cutting to the ground.

Mowing and cutting: Repeatedly cutting a plant to the ground, at least in theory, weakens the plant so that, eventually, it won't have the energy to re-sprout. This method works better with some species than others. With some species (e.g. well established Japanese knotweed), this process can take several years of diligence. Mowing does have the advantage of minimally disturbing the seed bank. It does, however, let sun reach the soil surface, so some seedlings will be encouraged but it is much less intrusive than digging. It's generally your best approach for the center of the patch and larger plants.

The important part of mowing is frequency. The plant must not be allowed to put out enough leaves to re-gain its energy or to go to seed. Otherwise, you're wasting your time (and possibly causing harm by the disturbance being done). For most invasives, at least monthly cutting is recommended. Start as early in the spring as possible.

Shade it out: Sun-lovers such as porcelain vine can be at least weakened by shade from larger plants. Here's where a fast growing but non-invasive cover-crops can be helpful once you've cut the bad guys down.

The magic ingredients: As you've probably figured by now, like with many things organic, the magic ingredients are persistence and patience. It is easier to prevent a major problem than to cure one. There's no "magic bullets"; use a combination of approaches over time, and tolerate a less than prefect result.

DRASTIC MEASURES: If all of the above fails, there are some other things you can try but they're more intrusive.

Sterilize the earth: You can destroy roots and the seed bank by sterilizing the soil. It does work much faster than hand-pulling or mowing. However, this is very drastic, since you kill everything, including the micro-creatures who keep the soil healthy, and the seeds of the native plants that we're trying to protect. So think it through: do not "destroy the village to save it".

Solar sterilization: This method works best for shallow-rooted plants in sunny locations. The way to do it: cut the offenders to the ground early in the season, and cover the ground with black plastic for the season. The sun heats the plastic and kills everything underneath, including the offending plant's roots and seeds. The following year, you can replant the area, hopefully with natives that provide wildlife food and habitat. Check your soil covering periodically during the season. Some times, you have to temporality remove the covering and re-mow the bad guys a few times.

If you don't have sun, a tarp or thick mulch could smoother the bad guys but it's also likely to take out the surrounding tree roots. So, again, think it through.

Fall paint-on herbicides: This method uses a very small amount of herbicides in a very controlled manner. It is still dangerous. In my humble view, any other use of chemical warfare against plants is likely to cause more harm than it prevents. What good is it to rid the woods of invasive plants if the frogs to get cancer?

How it is done: After cutting to the offender to the ground, particularly in late summer and early fall, when the plant is sending its store of energy down into the roots for winter, the stumps can be (carefully, carefully) painted with an appropriate herbicide (assuming that there is such a thing – I personally don't use them and won't know).

Always use 'cides sparingly, as a last resort, with great caution, and according to the label, see Issue 119 on using pesticides. Don't forget to:

• Follow the label –the law says that you have to exactly follow the directions on the label. This is a good law. Do it.

• Buy the smallest possible amount so that you don’t have left-overs creating a hazardous waste problem.

• Dilute per the label; they say that too strong a mix will kill the top of the root without get all the way down.

• Use protective clothing, gloves, and safety glasses, don’t spill any or let it get down the drain, etc.

• Dispose of excess chemicals, and used equipment, in a safe way.

• Do not use pesticides anywhere near water or wetlands; this can be a criminal offense as well as an offense against nature.

Biological controls: There are insects and fungi being tried as controls for some invasive plants, such as loosestrife. Generally, while you can even buy good bugs to control "bad" bugs, using biological controls for plants, is, I think, best left to the professionals such as the Agricultural Extension Service and the Forest Service. It is, though, good to be aware of activities in your area; since it is one more reason to not use insecticides.

Public lands, your garden, waste places: Where you're working also makes a difference. Since home gardens are usually relatively small, and since you regularly spend time in your garden, you have much more control over what goes on there, and can more freely use methods that require continued vigilance. As a general matter, activities on public lands should be conducted with the permission of the land custodian, and under the supervision of a competent professional. Before clearing waste places, like the vacant lot down by the corner, make sure that you've got the resources to follow through.