Carya laciniosa (Michx. f.) Loud.

Widely distributed but nowhere common (Schlesinger 1990), the Shellbark Hickory is a bold-textured tree whose leaves, fruits and buds are typically the largest of all hickories. It tends to produce a tall, narrow crown with ascending upper and drooping lower branches. Autumn colour is yellow-brown. Across most of its range it grows in fertile, moist, even periodically flooded ground, in contrast to the Shagbark. Especially in the northern part of its range it can also be found on dry sandy soils, hinting at adaptibility (Grauke 2003; Dirr 2009).

Carya laciniosa rather resembles C. ovata, though usually bigger in its parts and most commonly with seven rather than five leaflets. Leaf rachises often remain attached to the tree in winter. Like C. ovata, the bark separates into loose plates, the origin of the specific epithet, as well as an alternative common name, ‘Big Shagbark Hickory’ (Sternberg 2004). In C. laciniosa ‘shagging’ is usually less pronounced, with the edges of plates less obviously lifting away (Dirr 2009). The stout, orange-tinted branchlets and very thick husks are also distinctive.

This is a useful timber tree, whose strong wood (again, like C. ovata) is used for tool handles and furniture making as well as firewood (Schlesinger 1990). The Cherokee used both wood and bark strips in construction, took various parts of the tree as medicine and ate the nuts (Moerman 2019). The nuts are sweet tasting, though hard to crack and often considered less tasty than Shagbark nuts. They are taken readily by wildlife, especially squirrels. The parent tree of the 2014 collection WECA 32, in Edwin Warner Park, Tennessee, was a stout specimen of 1.2 m dbh, yet by early October only a dozen fruits were left to be collected. A few plantations have been established for nuts and more than forty cultivars named, mostly selected in Iowa or Pennsylvania, and all for their nut rather than timber qualities (Schlesinger 1990; Grauke 2003). It is advisable to plant at least two cultivars together for best pollination. We list a few cultivars suited to colder northern areas which are available from nurseries on both sides of the Atlantic.

Like other true hickories, it is slow to establish. A single seedling raised from WECA 32at Westonbirt Arboretum stood at 70 cm after 4 years in the ground. This tap-rooted species suffers from the usual hickory transplantation issues.

Carya laciniosa was first introduced to the United Kingdom in 1804 (Bean 1976). Though no originals are known, the tree in Tortworth churchyard, Gloucestershire, recorded by Bean (1976) as 10 m tall in 1905 and 20 m tall in 1964 remains in good health, if partially ivy-covered. A larger example grows in the less managed valley just north of the neighbouring Tortworth Court Hotel, although the tallest example in the United Kingdom grows in Aldenham Woods, Hertfordshire (28.5 m × 43 cm, 2018 – The Tree Register 2019). There are several large and beautiful specimens at Westonbirt Arboretum, where they can be compared with other accurately named species.

In continental Europe Shellbark has been less widely planted than Shagbark, although it is widely hardy. There is a splendid specimen in the Hortus Botanicus Amsterdam, planted in 1912 (monumentaltrees.com 2019). Well to the east is a group planted at the Kórnik Arboretum in western Poland around 1873, which had reached maximum dimensions of 29 m in height and 51 cm in diameter by 2018 (Rudawska et al. 2018). Outside its native American range, it is well-suited to the Pacific Northwest, where two specimens planted in 1928 can be seen at the Hoyt Arboretum, Portland, Oregon (Hoyt Arboretum 2019).