Ulmus hollandica 'Pioneer' is a fast-growing American selection that is fairly resistant to Dutch elm disease. It has a spherical crown and grows to a height of 15 - 18 m. 'Pioneer' has dense foliage, which gives it a closed crown. The twigs are light grey with green stripes. The large, glossy, dark green leaves measure 9 - 15 cm and are elongated in shape. The leaf edge is double-serrated. The yellow leaves remain on the tree for a long time in the autumn. Winter hardiness zone: 5a