Vacant Islands

Island	Crops that can grow in it	Merchant Location	WIP
Vacant Grassland Island	Emerald Tree, Spring Tree, Cotton, Alabaster Bush, Wheat, Garden Mushroom	Fort Finch
Vacant Forest Island	Cotton, Alabaster Bush, Wheat, Dark Fir, Garden Mushroom	Fort Finch
Vacant Dry Desert Island	Desert Fruit, Cactus	Fort Finch
Vacant Oasis Desert Island	Desert Fruit, Cactus, Sand Palm	Fort Finch
Vacant Fairy Forest Island	Pumpkin, Carrot, Ruby Tree, Gold Glimmer Tree, Alabaster Mushroom	Fort Finch
Vacant Toxic Island	Amber Bell, Big Bloomer, Swamp Shroom	Mount Meridian
Vacant Swamp Island	Amber Bell, Big Bloomer, Swamp Shroom, Ghost Gingko	Mount Meridian
Vacant Coastal Island	Aloe, Fruit Palm, Beach Palm, Palm, Sweet Potato	Mount Meridian
Vacant Tropical Island	Sweet Potato, Aloe, Palm, Fruit Palm	Mount Meridian
Vacant Polar Island	Frost Lily, Fir, Bitter Oak, Silk Cocoon	Mount Meridian
Vacant Crystal Island	Wonder Crystal, Flying Wonder Crystal, Magenta Berry Bush, Corundum	Great Frontier
Vacant Hollow Lands Island	Wondrous Geode, Magenta Berry Bush, Cluster Crystal	Great Frontier
Vacant Volcano Island	Blazing Palm, Peak Hip, Blazing Chili	Great Frontier
Vacant Red Planet Island	Jelly Belly Bush, Cobalt Leek	Great Frontier
Vacant Asteroid Island	Starlight Tube, Cosmic Mushroom	Great Frontier
Vacant Lunar Elf Island	Birch Tree Seed, Ginkgo Tree Seed, Garden Mushroom Seed	Farran-Enore Main Quest
Rainbow Island	Emerald Tree, Spring Tree, Cotton, Alabaster Bush, Wheat, Garden Mushroom	DLC

There's also a "Title Deed of Vacant Lunar Furfolk Island" that is unlocked after completing all 3 portal missions and can be bought from Wildhowl for 40,000 defender coins.