Mistletoe is a parasitic plant. It’s like ticks on a dog. It gains its sustenance from the host, and there’s no way you can say that that’s a good thing. What trees are most commonly impacted? Many types of trees may show up wearing mistletoe for the Christmas Ball, but most common among them are cedar elms, hackberries, bois d’arcs, pecans and red oaks. Among those, cedar elms and hackberries make up the vast majority of the invasions. How does it get started? Mistletoe seeds are attractive to birds.