These seedlings come from known heartnuts, but are from random mothers.
Many heartnut seedlings revert back to Juglans ailantifolia and not Juglans ailantifolia var. cordiformis. That is, their nuts will resemble the thick-shelled Japanese walnuts. Some heartnut seedlings have a 70% chance of being just Juglans ailantifolia rees. Also those seedlings produced from the best heartnut parents will produce up to 90% heartnut offspring. Therefore we cannot 100% guarantee a true heartnut is produced.