Lettuce seeds are tiny, dry fruits (achenes) that vary in color (white, gray, brown) and contain a single seed, each tipped with a feathery "parachute" for wind dispersal, growing into diverse leafy plants (like crisp iceberg, soft butterhead, or frilly loose-leaf) known for their cool-season preference, ease of growth, and nutritional value, thriving in well-drained soil with ample moisture and sunshine, and ready for harvest within 6-10 weeks, depending on the variety.