Native to northern China, Korea and Japan, the Chinese elm (Ulmus parvifolia) demonstrates a wide tolerance to soil types and climate. Showing resistance to the Dutch elm disease that plagues the native American elm, Chinese elm provides shade in landscapes with dry or compacted soils. Normally winter hardy only in U.S. Department of Agriculture hardiness zones 5 through 9, winter cold determines how much a tree sheds leaves in fall. Overall, the Chinese elm typically grows as a semi-evergreen to fully deciduous tree.
In USDA zones 5 through 8a, the winter temperatures cause Chinese elms trees to lose all of their leaves no later than very late fall. Often the leaves develop a bit of yellow colour or remain dark green and immediately shed without changing. In USDA zones 8b and 9, where the winters are much milder, Chinese elms often only partially shed their small oval leaves -- making them partially deciduous or semi-evergreen. In the southern U.S., Chinese elms may be more frequently called evergreen elms.
Several cultivars of Chinese elm exist today for landscape designers and gardeners to choose for their properties' scale and size. Some selections tend to lose most or all of their leaves in fall based on temperatures. For example, Emerald Isle, Emerald Vase, Hokkaido, Burgundy, Dynasty and Prairie Shade cultivars tend to become semi-deciduous in the southern U.S., while fully deciduous farther north. In southern California, and along the Gulf Coast, nearly evergreen selections Drake, True Green and Sempervirens retain much more foliage across winter, but expect some leaves to drop.
Fall Foliage Coloration
Chinese elms aren't well known or prized by gardeners for their ornate fall foliage. In fact, often the leaves only attain inconsistent yellow-green colour before dropping. This species naturally holds onto its leaves late into fall, so fall frosts readily kill the foliage and cause it to drop before any yellow pigments manifest. According to the University of Connecticut Plant Database, in the southern U.S., the longer fall season with milder bouts of cold allows some Chinese elms to attain a bit more yellowy brown foliage before leaves shed. Often leaves still drop when mostly dark green.
From a distance, people confuse and mislabel Chinese elms as Siberian elms (Ulmus pumila). Both trees grow in tough conditions, but the latter species tends to be messier with shedding twigs and seeds and well as branch breakage in windstorms. Siberian elms' seeds sprout like weeds and become noxious in many parts of the U.S. Siberian elms always become fully deciduous in winter, and are more cold resilient. In USDA zones 3 and 4, chances are you see a Siberian elm, not a Chinese elm.