I like Nastarana's idea of the walk. Makes it obvious what side is theirs and just what they need to maintain up too. I am redoing an area and have a similar issue, I am going to leave that 12" and then level my side with a low stack block wall. I have a section that is wider than the 12" behind one of our fenced gardens. I can maintain my side no problem and have gates. I do have a question for those in the know, if your neighbor has left themselves NO access other than trespassing across all of your property to maintain their fence, do you have to allow or should they purchase their own ladder? The bad neighbors will have their fence fall any old time, surprised it is still standing to be honest, and we have our own chainlink fence on our side. But the over watering towntown group has left themselves no way to access except thru our side I have lots of things planted on our side of the line, most by 2 or more feet so there is work room, just no way to reach it. That fence will probably be the first to fall because of the winds even though it is in better shape. (but only by a little bit) And is there anything that can be done if they leave the old concrete around where their fence was before? They built one guessing on the wrong line and rebuilt a new one more on their side but I have trip hazards all over on our side of the fence but I think mostly on their side of the property line.

Those are Giant White Flies, a terrible pest we have here in S. California, serge. They have particular plant favorites - hibiscus, canna, xylosma. So much so, many S. California gardeners have refused to plant those 3 above plants, for fear of harboring Giant White Fly in their yards. They are extremely difficult to eradicate. Here is some information on them, and how to manage them in your yard. I would also talk with your local Master Gardeners and better garden center on tips on management. Sorry, Steve, this is not a harmless pest for us in S. California, and what you have may not be what we have here in S. California. Better to try to avoid insecticides, as they can also kill beneficials, such as lace wing, lady beetles, syrphid flies, and parasitic wasps. Try removing infested leaves, look under leaves for the distinctive concentric white whorls of eggs. Wash those off with water and insecticidal soap (in the evening, to help protect certain beneficials). Remove leaf droppings, and apply worm castings to help affected plants recover faster. There is a product called Naturalus T & O that is organic, and supposed to be very effective, but it is rather expensive. Some folks have even resorted to vacuuming up large amounts of adults, to reduce adult populations. You can also try Neem oil to smother the nymphs, although I am not sure of the efficacy. It certainly won't hurt, as long as you apply in the evening, and temps are below 85 degrees. This is the season to see adults massing to lay eggs, so you're catching the infestation at a good time. I would start searching your yard to see if you have infestations in the more preferred plants, and start your clean up, there. Patty S. Here is a link that might be useful: UC IPM: Giant White Fly

Bleach is one of the safest things you can use to eradicate unwanted plants/weeds because it does not persist for any length of time in the environment. It is amazing the amount of misinformation that gets spewed about online. Unfortunately, a lot of it remains there unchallenged and picked up, repeated and recycled and worse......often acted upon, to the detriment of our environment and sometimes ourselves. Chlorine bleach poses a significant risk to the environment, and chlorine was even used as a chemical weapon during World War I. Many countries have banned chlorine bleach or restricted its use in an effort to protect the environment and human health. As an example of bleach's persistence in the environment, manufacturers who use chlorine bleach as part of the processing, cleaning or sterilization processes often release it into local water bodies along with other liquid industrial waste. Once it reaches the water, chlorine reacts with other minerals and elements to form a host of dangerous toxins. These toxins, including dioxins, furams and PCDDs are often referred to as "persistent organic pollutants" because they linger in the water or soil and take many years to disappear. Greenpeace calls dioxin one of the most dangerous chemicals known to science, and warns that it can contribute to cancer, endocrine disorders and other serious health effects. The West Virginia University Extension also links chlorine-based compounds, like dioxins, with low sperm count, testicular cancer and breast cancer due to their ability to mimic human hormones. So you guys who are so ready to start spraying chlorine bleach all over the place may want to reconsider your choices :-) DON'T use bleach as a herbicide. It is not registered for that purpose so technically it is illegal to use it in that manner. Second it is a caustic, corrosive agent that is damaging to all manner of beneficial soil insect life, amphibians and aquatic life and any mammals it might come into contact with. It is also extremely alkaline and can negatively impact soil pH, making it difficult to grow any plant in any area so treated. If you must, use a registered herbicide - like RoundUp or similar - according to label directions. Here is a link that might be useful: bleach is not a herbicide

Amyta, find the larger roots which are the remains of the tree and remove some dirt from around them. Use a drill and use a paddle or spade bit. Drill into the root, do not drill through, just drill out a wide hole. Fill the hole up with Round-up BRUSH concentrate. It will spread throughout the root system and kill them all. Thus ends your sprouting problem.