Will weed-control products keep flower seeds from germinating?

NEW LONDON, OHIO Linda Barnes

Melinda: Preemergent weed killers prevent both weeds and desirable plants from sprouting and growing. Postemergent weed killers are used to kill existing plants. These are typically used on lawns, not gardens, where desirable plants can be damaged. Contact weed killers, both organic and synthetic, damage or kill any good or bad plants they touch. Always check the label before using any chemical in your garden or landscape. If you can’t find the information you need, contact the manufacturer—its name and phone number should be on the packaging.