Miss Penny and Mr. Grubbs

``As ye sow, so shall ye reap'' could be the moral of this engaging picture book. For 48 years, Miss Penny's prizewinning vegetable garden has been the envy of sour neighbor Mr. Grubbs. But Grubbs sees to it that this summer will be different; at night he sets loose hungry rabbits in his unsuspecting neighbor's yard. Miss Penny tries every known anti-rabbit device, but to no avail: before long, her flourishing crops are decimated. Grubbs's produce fails as well, since he directed all his attention to destroying Miss Penny's garden rather than caring for his own. In a neat twist, Miss Penny comes out a winner and Grubbs gets an ironic comeuppance. Ernst's ( When Bluebell Sang ; Ginger Jumps ) jovial illustrations, with their pleasingly plump contours, take an equal share in telling this original tale. The sight of a dismayed Miss Penny surrounded by pudgy rabbits will delight even the most bunny-weary reader. Ages 3-7. (Apr.)