previously answered...bumping down...

Is it a vine? It may be Solanum jasminoides, or potato vine. I lived for over 20 years in Northern CA and only one time did I see pokeweed, but don't know if poke grows in the Central Valley (I know the climate is definitely not the same there as in Sonoma!) But Potato Vine seemed to be pretty much a universally used fast, thick grower for problem areas. The individual blooms will look a bit like those of tomato plants, and its purple berries are small. Stems and foliage often take on a purple tinge depending on light exposure. Folks either love it because of its vigor and reliability or hate it because it's "overused."

I've read that crabapple trees can be planted under, and the 20' x 25' one in our back yard has no surface roots at all after 30 yrs. The only thing I've planted under it is a Kousa 8 ft. away from its trunk and didn't run into problems digging out any underground root masses (unlike my maples, which have awful roots above & underground). There are lots of very disease-resistant varieties out now; some are dwarf like 'Camelot' (10 ft.). I understand 'Robinson' is one of the fastest growers. If you cut & paste this link, and scroll down to the chart, it gives a lot of valuable info on many of the new crabapples out there: http://www.ces.ncsu.edu/depts/hort/consumer/factsheets/trees-new/cultivars/mallus_hybrids-table.html

I agree that solid privacy fence is probably the best option, even if he/she just does that one section of view. Another thought of mine was to plant a tree like swedish columnar aspen. My initial thought was that you can keep it narrow at the base and then let it grow wider near the top, but this probably wouldn't work, since near the bottom is where they want the privacy and these trees are somewhat just bare trunk near the bottom. Cedars wouldn't work as well, unless perhaps thuja occidentalis 'degroots spire' cedar but even then it would take a while to gain any height (not to mention expensive to try to make a hedge out of many of them, might as well buy a section of privacy fence). Maybe lattice and an aggressive yet dependable vine like virginia creeper? Dropmore honeysuckle? The only downside with any vine is that in early spring, late fall and winter there would be no leaves so poochie would be able to see through. Hard to believe he/she doesn't bark when he just hears the kids as opposed to seeing them. I'm no dog trainer but perhaps the owner has to get involved and start scolding him when he growls at the fence? Somehow make him understand the kids are not in his territory? I wonder if he's one of those dogs that's just left outside alone all the time, which can lead to behavior problems too. Anyways, I hope there's a solution as I can't imagine it's pleasant for the kids to be growled at in their own back yard, nor for the neighbors who probably listen to the dog barking. Glen