Something's always happening in a garden. Sooner or later, it all turns to compost, including the gardener. After growing ornamentals a dozen years on a rocky hard clay slope, the queen of gardening gaffes confesses why: ''I don t do bugs, the buck stops here, some plants are X-rated and God will get even with you; attacks from crape murderers and a fat chance of rain may lead to horticultural holocaust and a decent burial; attitude is everything in a pricey pa$t-time that sure beats a shrink, may be in the genes and have one asking, 'Can this disease be cured?' ''