Apple Rootstock Info: Mark

An open-pollinated seedling of M.9 and introduced by Michigan state University, USA in 1979. It is a virus-free clone of MAC-9. Mark is a hardy, precocious dwarfing rootstock. It is susceptible to fire blight and fairly resistant to crown and root rots, produces many burr knots and few root suckers. Mark requires tree support. Trees are very precocious and tree vigor may decline earlier than desired when young trees are allowed to produce heavy crops before attaining the desired tree size. Root Mass Proliferation (RMP) is the name of the syndrome often observed in older trees on Mark. RMP is a tumorous swelling at the ground line or below ground that is often observed in this rootstock, and accounts for its highly variable performance both within and between orchards. RMP often results in a lack of uniformity in fields. Mark is also particularly drought sensitive, and irrigation is recommended even in areas where it is usually considered optional. On the proper site Mark can be a very productive rootstock, as numerous Michigan growers have experienced. Mark was evaluated in several NC-140 trials and it has been planted in commercial orchards throughout the eastern U.S. Trees on Mark were usually about 30 to 50% as large as trees on M.9 NAKBT-337 and yield efficiency was usually higher than on M.9 NAKBT-337. Although mark performance has been variable in the eastern U.S., it has performed poorly under hot dry conditions in the western U.S.