Yaupon holly (I. vomitoria) is also best left unpruned; however, trimming holly bushes like these can be done when absolutely necessary to maintain appearance. Wait until dormancy for heavy pruning or simply trim as needed for shape.

I've had a dwarf yaupon holly hedge in the front for about 20 years. I trim them to a nice rounded shape with battery operated hedge shears (one of my favorite tools) after their spring growth spurt. But as PJ says a light trim can be done anytime to shape them and maintain appearance, but if trimmed a lot they will be slow to fill back in until cooler weather.

About three years ago I decided my hedge was getting too tall and uneven; some bushes were taller than others. So in very early spring I took the chance of trimming them quite a bit to even out their height and shorten them. I took about 8 inches off some of the bushes. Nothing but bare twigs were showing along the top, but in a few weeks they had filled in nicely. I gave them a little fertilizer to help them along.

Another little tip -- even though dwarf yaupon holly is drought tolerant make sure it's getting some irrigation in this drought. I had never watered mine before we took out the lawn in front and put in gravel and guess what ... they missed getting the water from the lawn and a few branches died before I realized what was going on. I put in a drip irrigation line under them and now they get watered about every two weeks.

We didn't trim our Dwarf Yaupons until they were mature at about 20 years old and now we trim them every other year or so in the spring. They were very out of shape so we cut back quite a lot and it didn't hurt them a bit because they leafed out right away. I don't even think you could tell even with a lot cut off. Now just a light shape up is all they need. I leave the ones along the front of the house pretty natural and not sheared. Leave the top narrower than the bottom so the whole shrub can get light and you should be good.

There's one in the garden that I like to clip into a soft round shape so either look works with the Dwarf Yaupon.

Really, you can't hurt them trimming in the spring because they do grow back. If you trim them in the fall they won't leaf out as quickly so you'll have some bare stems.

Here's a link that gives a pretty good description

Here is a link that might be useful: Trimming Dwarf Yaupon

Thank you all.

I wouldn't even be thinking about trimming them, except that one of them has grown over the driveway...