Presented by Master Gardeners of Cornell Cooperative Extension. Here’s how the swap works: Pot up your plants on or before May 21st. Drop off your plants to be swapped on Saturday morning between 9:00am and 10:00am. Swappers will receive vouchers for the number of plants they drop off. Swappers return at 11:00am to swap vouchers for plants! At 11:30am the swap will open to the public for the plant sale.