Brass shrub spray? Not worth it. Now, if all the shrubs are shorties, you could use as little as four or five (if your pressure is low, use five, spaced twelve or so feet apart) Rainbird 1812 high-pop mist heads with strip-pattern nozzles. (15EST/15CST or 15SST/15RCS/15LCS) - Total water comsumption will be less than 5 gpm, and the full coverage will allow you to place annuals in the bed, should you wish. Hunter makes side-strip nozzles, like Rainbird's but with a bit wider coverage (5x30) Since your shrubs aren't planted smack against the edge of the bed, you don't need to spray water on the foot or so near those edges.