Haiku seem to be regaining the popularity they enjoyed in the mid-60s, but today picture-book authors are writing their own (see Caudill, above). Betsy Maestro returns to the 17-syllable form which even the translations of Lewis Keats' In a Spring Garden played free with. But otherwise she tries so hard to keep the subjects familiar and the statements simple that the flash and intensity which make haiku fun to begin with are smoothed over. Not all of the observations are as prosaic as ""We ate a kumquat/Planted a seed and waited./ Now we have a tree""; elsewhere Maestro points out a ""quiet cardinal/ . . . like a bright red ribbon"" and a ""Brown furry rabbit,/ Its nose wiggly as jelly."" Yet the total impression, sustained in husband Giulio's chunky shapes overlaid in light yellow, brown and pink, is of a cheery and serviceable nursery blanket. . . fine in its place but potentially constricting for youngsters ready to move out on their own.