The term heirloom carries many connotations. In fact different definitions exist between different plants. Generally, true heirloom tomatoes are said to be open pollinated varieties that have been in existance since WWII. That has been stretched to include almost any open pollinated varieties. Unless you plan to save seed, there is nothing to worry about. Brandywine, being potato leafed, has a characteristic which can help you. The potato leaf gene is recessive and any crosses with Brandywine and regular leafed varieties will result in regular leaf plants. Just cull out any plants that don't have the potato leaf and Voila! The husk tomato may be (probably is) too distant a relative to cross Brandywine, anyway. Don't let my over cautious warning slow you down. Remembr I'm trying to protect and distribute a 400 variety collection and have to be super cautious. Good gardening, Chuck Wyatt http://www.heirloomtomatoes.net