Best grown in moist, organically rich, well-drained loams in full sun. Best sited in locations protected from strong winds. Generally tolerant of urban conditions, particularly if well-sited in the landscape. Tolerant of neutral to slightly alkaline soil conditions.
Fraxinus americana, commonly called white ash, is native to eastern North America. In Missouri, it typically occurs in dry and rocky upland woods, glades and moist low woods along streams, bluffs and slopes throughout the state (Steyermark). This is the largest of the native ashes, typically growing 60-80’ tall. Young trees are pyramidal in shape, gradually maturing to a more rounded crown. White ash is primarily dioecious (separate male and female trees). ‘Rosehill’ is a seedless, broad-conical cultivar that typically grows 35-50’ tall. Inconspicuous purplish-green flowers appear in spring. Foliage consists of odd-pinnate compound leaves with 7 leaflets (less frequently 5 or 9). Each oval to oblong-lanceolate leaflet (2-4” long) is dark green. Variable fall color ranges from attractive bronze-red to drab bronze-yellow. Gray bark develops distinctive diamond-shaped ridging on mature trees. U. S. Plant Patent PP2678 was issued on October 11, 1966.
Emerald ash borer is native to Asia. It was first discovered in the U. S. (southeastern Michigan) in 2002. It has now spread to a number of additional states in the northeast and upper Midwest, and is expected to continue spreading. Emerald ash borer will typically kill an ash tree within 3-5 years after infestation. Once infestation occurs, it is very difficult to eradicate this pest which feeds under the bark and bores into wood. This borer now constitutes a serious threat to all species of ash in North America. On March 8, 2012, the National Park Service announced that the 900 'Rosehill' white ash trees now growing on the Gateway Arch grounds in St. Louis, Missouri will be removed primarily in anticipation of the inevitable arrival at some point in the future of the emerald ash borer to the St. Louis area. White ash trees are generally susceptible to a number of additional insect problems including ash borer, lilac borer, carpenter worm, oyster shell scale, leaf miners, fall webworms, ash sawflies and ash leaf curl aphid. Potential disease problems include fungal leaf spots, ash leaf curl, powdery mildew, rust, anthracnose, cankers and ash yellows. General ash decline is also a concern. Brittle branches are susceptible to damage from high winds and snow/ice.
Planting new ash trees is no longer recommended given the susceptibility of this tree to the emerald ash borer. Ash trees have typically been used over time in a variety of applications including shade tree, street tree or lawn tree.
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Missouri Botanical Garden
4344 Shaw Blvd., St. Louis, MO 63110(314) 577-5100 hours and admission
Butterfly House
Faust Park, 15193 Olive Blvd. Chesterfield, MO 63017(636) 530-0076 hours and admission
Shaw Nature Reserve
Hwy. 100 & I-44 Gray Summit, MO 63039(636) 451-3512 hours and admission