Ten-Year Survival and Growth of Platanus Progenies

Western American planes (P. racemosa Nutt. and P. wrightii Wats.) suffered annual dieback in replicated Maryland test plantings. Many Turkish planes (P. orientalis L.) were killed back during the severe winters of 1977-78 and 1978-79 with overall survival of only 18%. Hybrids between P. orientalis and P. racemosa were completely killed during these winters. On the other hand, hybrids between P. occidentalis L. and the other 3 species had high survival (81 to 100%).

Growth rate of hybrids between P. occidentalis and P. orientalis (the “London” plane cross) was slightly but not significantly superior to that of P. occidentalis, even though the hybrids were far more resistant to sycamore anthracnose disease. Likewise, the high disease susceptibility of the hybrids involving Western species was not reflected in significantly slower growth. All the hybrid progenies averaged between 19 and 22 feet in height after 10 years. Four of the best anthracnose-resistant hybrids were selected for more extensive testing and 2 of these will be introduced as cultivars.

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