
Buartnuts (Juglans x brixby) are a hybrid between the butternut (Juglans cinerea) and the heartnut (Juglans ailantifolia) and have the flavour of the butternut and hardiness of the both. They occur naturally in the USA where heartnuts have been planted alongside the native butternut, however you need grafted cultivars to get the best nut.
Like all walnuts they need good drainage and deep soil in a sunny position, protection from frost in the first couple of years is a good idea, trees can reach 10-15m high and 10m wide.