By Liz Baessler The heartnut tree (Juglans ailantifolia var. cordiformis) is a little known relative of the Japanese walnut which is beginning to catch on in the colder climates of North America. Able to grow in areas as cold as USDA zone 4b, its a great alternative where many other nut trees wont survive the winter. But what are heartnuts? Keep reading to learn about heartnut uses and heartnut tree information. Heartnut Tree Information Heartnut trees can grow to 50 feet tall (15 m.) with a spread of 65-100 feet (20-30 m.). They are hardy to cold and most pests. They get their name from their prolific production of a nut that looks, both inside and out, like a heart. The nuts taste similar to walnuts and are extremely hard to crack open. Growing heartnuts in well-drained soil will produce the best results, but they will grow in loamier soils.