Q: $ i have a lot of trouble every year setting parsley seeds to sprout. What's the secret to success with them? A: Soak the seeds in warm water for 24 hours before planting and they'll germinate much sooner. After planting, they need 16 hurs daily at about 68 degree F. and eight hours at about 86 degree. Plant them about 1/4-inch deep in individual peat pots, which can be planted outdoors soon after the late frost. The seeds need complete darkness to germinate, so cover the pots with newpapers. They should gerninate in 11 to 28 days. Do you know where I can buy seeds for wildflowers, particularly black-eyed Susan? A; They're listed in the catalog of Native Seeds, Inc., 14590 Triadelphia Mill Road, Dayton, Maryland 21036. Write and ask for a free catalog. Can you tell me where mushroom spawn can be purchased? I'd like to try growing some mushrooms. Look in the catalog of Burpee Seeds, Warminister, Pa. 18991. You can write away for it; it's free. Q: I want to plant a European mountain ash in my front yard but have been warned it's too hard to grow. Do you consider the risk too great. A: If this tree is not protected from borers it will probably be killed just about the time it reaches its peak of beauty. It is also susceptible to canker diseases, which are difficullt to control, and prevention is necessary for survival. But the tree has great ornamental value, especially in fall. Q: Is it necessary to cut off the faded flowers of rhododendrons ? A: Rhododendrons growing wild bloom beautifully every year, and no one picks off their faded flowers. However, it's generally true that if faded flowers are allowed to stay on and form seed pods, the vitality of the planting will be lowered because food (energy) used in seed production would be conserved.