Ask Mr. Smarty Plants

There are 11 members of the genus Equisetum, horsetail, native to North America, of which 5 are native to California. Since they all have similar habits, we will use Equisetum hyemale (scouring horsetail) as an example. According to this USDA Plant Profile map, it is native not only to Los Angeles County, but also to every state in North America, Alaska and provinces in Canada, as well as Greenland, so we can be assured that it will thrive in your area. But that really wasn't what you wanted to know; you were asking if it could be aggressive, so we'll look a little further for that.

We already know that this is a moist places, standing water plant, and is considered definitely invasive in those spots. But we thought that perhaps being planted in a planter would minimize the danger of that. However, before you make a decision, you should read the comments in this Dave's Garden forum on Horsetail scouring rush. It is not a pretty picture.

You can get more information from this article on Equisetum hyemale by Earl J. S. Rook, including the fact that it spreads both by rhizomes and by spores.  This sounds like if the right hand don't get you, the left hand will. From the comments we saw, you probably are not too safe thinking you will just give it a try, and see how it does, because apparently, once you have it, you HAVE it.

Generally speaking, we feel that the best way to control invasive plants is to never plant them.