My two little munchkins recently started doing this too (they're 8 months old and I guess they're becoming little men!
Of course, since they're still puppies and are hilarious the way they do it, I think it's adorable... I'm sure I wouldn't think so once my plants started dying though!
What I did was similar to the fence suggestion... I bought a bunch of those little 18" high garden edge type fences. It does the trick of keeping them from spraying directly onto a plant, so now they mainly abuse various trees in the wooded section of our lot.
However, I wouldn't get the shocker one as that is, in my opinion inhumane.
I was adamant about this too, and in fact we were going to get a physical fence... until we were getting price quotes of $8k and more.
We decided to give the invisible fence a try (the company called "Invisible Fence" -- not one of the cheaper knock-offs) because they said it wasn't this big cruel shock, but just a mild static shock like if you touch a doorknob and get a little zap.
I insisted on walking through the line wearing the collar on my arm to see what it felt like... and they were right, just like when you shock yourself on a doorknob or something, it's surprising and unpleasant, but definitely not cruel or inhumane. It's been the best thing for our pups... they were trained to turn away just when they hear a beep, so I don't even know that they've ever felt the zap, and they're blissfully free to run the full acre property.