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Published In: Systema Naturae, Editio Decima 2: 1272. 1759. (Syst. Nat. (ed. 10)) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 8/25/2017)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Native

 

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1. Juglans cinerea L. (butternut, white walnut)

Pl. 431 d–f; Map 1932

Plants trees to 30 m tall. Bark light gray or grayish brown, shallowly divided into smooth or scaly plates. Pith dark brown. Terminal buds 12–18 mm long, conic, flattened. Leaf scars with the upper margin straight or nearly so, bordered by a well-defined, tan to gray, velvety ridge. Leaves 30–60 cm long, the petiole 3.5–12.0 cm long, glandular-hairy, with (7–)11–17 leaflets, including usually a large terminal leaflet. Leaflets (2.5–)5.0–11.0(–17.5) cm long, 1.5–6.5 cm wide, ovate to lanceolate or oblong-lanceolate, more or less symmetrical (not appearing asymmetrically tapered), mostly rounded at the base, tapered at the tip, the margins finely toothed, yellowish green, the upper surface with scattered fasciculate hairs or becoming nearly glabrous at maturity, the undersurface with abundant 4–8-branched hairs (the branches appearing fasciculate) and yellowish scales, sometimes also with gland-tipped hairs, the axils of the secondary veins with prominent tufts of fasciculate hairs. Staminate catkins 6–14 cm long, the staminate flowers with 7–15 stamens, the anthers 0.8–1.2 mm long. Fruits usually in clusters of 3–5, 4–8 cm long, ellipsoid to ovoid or more or less cylindrical, the husk smooth, densely covered with gland-tipped hairs, becoming slightly wrinkled and papery with age. Nuts 3–6 cm long, ellipsoid to ovoid or more or less cylindrical, with about 8 high, narrow, irregular, longitudinal ridges, the surface between the main ridges with narrower, interrupted, longitudinal ridges or folds. 2n=32. April–May.

Formerly scattered nearly throughout the eastern 2/3 of Missouri, becoming increasingly uncommon (eastern U.S. west to Minnesota and Arkansas; Canada). Bottomland forests, mesic upland forests in ravines, bases of bluffs, and banks of streams and rivers.

Butternuts are difficult trees from a silvicultural perspective. They never form large stands but instead occur as scattered trees within their habitats. They are relatively intolerant of human disturbance, but they do not reproduce well in closed-canopy forests (Ostry et al., 1994). In recent decades, many trees have been killed by butternut canker, Sirococcus clavigignenti-juglandacearum Nair, Kostichka & Kuntz, a fungus that kills trees by girdling the limbs and trunk (Ostry et al., 1994). As a result, this imperiled species is becoming very uncommon throughout its range. Some of the butternuts in the horticultural trade apparently are hybrids between J. cinerea and the closely related Japanese walnut, J. ailanthifolia Carrière, which have improced resistence to the pathogen. These are not yet known to have escaped into the wild in Missouri, but are nearly impossible to distinguish from genetically pure butternut trees morphologically.

 


 

 
 
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