‘Garbage gardening’’ is an easy and inexpensive way to grow flowers and edibles using kitchen scraps — the pits, seeds and roots that otherwise would be headed to a landfill. It’s a fun way to recycle. Educational for the kids, too. ‘‘Almost every unprocessed fruit or vegetable can be grown into a decorative houseplant,’’ said Deborah Peterson, coauthor of ‘‘Don’t Throw It, Grow It.” ‘‘Some are perennials, others are annuals or biennials,’’ Peterson said. ‘‘You…