The often unappreciated allium, and our relentless quest for the perfect green lawn are covered on HomeGrown this week. Mark McDonough tells of his remarkable 30 years of research on the allium (the ornamental onion); there’s more to this genus than the big, purple Globemaster. Later, Ted Steinberg tries to explain our collective fetish over the elusive, perfectly manicured, weed-free lawn, a topic he covers in detail in his book, “American Green: The Obsessive Quest for the Perfect Lawn.” Downloadable MP3Find out more: