Note that, post Brexit, nurseries have warned that they will not be able to deliver plants from the UK to the EU or vice versa. Seeds should not be affected.
‘Plants with Purpose’ and ‘Appletreeman’ can both be found at plantsandapples.com and between them supply many useful plants for the forest garden. They are based in Perthshire.
Scottish Heritage Fruit Trees sell a wide range of, er, Scottish heritage fruit trees.
Glendoick Garden Centre sells traditional fruit tree and soft fruit species suitable for Scotland.
Poyntzfield Herb Nursery, based in the Black Isle, supply both seeds and plants of medicinal and culinary herbs, broadly defined.
Graham Bell is a long-established Scottish forest gardener, based in the Borders, who now sells forest garden plants through The Red Shed Catalogue.
Ann Miller’s Speciality Mushrooms is the place to go for mushroom spawn.
Kevock Garden Plants mostly supply ornamental plants but their range includes some that are useful for the forest garden.
England and Wales
The Agroforestry Research Trust have the UK’s widest range of forest garden plants. They do both plants and seeds.
Edulis is in Berkshire and also supply both plants and seeds.
The Kore Wild Fruit Nursery in Wales has wide range of fruit.
Crûg Farm, also in Wales, do ornamental plants plus some useful species for the forest garden.
The Edible Garden Nursery, in Devon, does what it says on the tin, with an excellent range of pot-grown plants, focussing on herbaceous perennials but with some annuals, shrubs and trees too.
Chiltern Seeds are based in Cumbria and have a wide range of seeds, including both ornamentals and useful plants. Where B&T World Seeds (below) and Chiltern both have a variety, Chiltern is usually cheaper for UK delivery. Their catalogue is worth getting for its entertainment value alone. A similar seed supplier worth checking is Plant World Seeds.
B&T World Seeds are based in France and carry a huge range of seeds. If you can’t find it anywhere else, try B&T.
Myrrhis Permaculture Garden in Denmark supply seeds of perennial vegetables. The site is in Danish but autotranslate, Latin names and pictures make it usable without needing to go to Danish classes.
Nurseries in Canada often deliver to Europe and the US
Fiddlehead Nursery in Ontario specialises in plants for edible landscaping. I have had excellent results with their seeds.
Richters Herbs, also in Ontario, supply edible and medical herbs as plants to Canada and the US.
Nurseries in the US usually only take orders from within the US for both plants and seeds.
Cultivariable have a great selection and lots of useful advice on Andean root crops.
Edgewood Nursery in Maine specialise in unusual edible plants, which they supply as both plants and seeds.
Perfect Circle Farm in Vermont supply nut trees, fruit trees and berry shrubs.
Edible Acres, in New York state, sell plants for all layers of the forest garden, wither in pots or as bare root plants.
Tripple Brook Farm, in Massachusetts, sell a wide range of plants in pots, with an emphasis on those native to the region. Many of them are useful perennial edibles.
Oikos Tree Crops, in southern Michigan, sell not just trees but also soft fruit and some perennial vegetables. They have an American persimmon from northerly seed sources for northerly gardens. They only sell plants within the US but their website says that they will send seed outside at the buyers risk.
One Green World sell fruit, nuts and perennial vegetables as plants or tubers from Portland, Oregon.
In Washington state both Burnt Ridge Nursery and Raintree Nursery sell fruit and nut trees and soft fruit. Raintree have a few other unusual edibles besides. Far Reaches Farm sell perennials in pots. They are not specifically for edibles but have a very wide range and come up in a lot of my searches for the more obscure plants that I am trying to get hold of. I just wish they delivered to Scotland!
Chileflora, a website about the flora of Chile, has an associated shop which supplies seeds from this cool temperate corner of the southern hemisphere to the rest of the world.