Juglans hindsii, commonly called the Northern California black walnut and Hinds's black walnut, is a species of walnut tree native to the western United States (California and Oregon).[ Jepson Herbarium (2013): Juglans hindsii][ Calflora: Juglans hindsii . 10.1.2013] It is commonly called claro walnut by the lumber industry and woodworkers, and is the subject of some confusion over its being used as rootstock for English walnut.
Description
Juglans hindsii is a large tree that grows up to tall
and may reach over with enough shade. The species normally has a single erect trunk, commonly without branches in the lower half of the tree, and a crown that can be wider than the tree is tall. Trunks may reach in diameter near the base of the tree.
The leaf is approximately long, with 13–21 leaflets per leaf, each long, with dentate margins.
The species is monoecious, with male flowers in yellow-green catkins up to long and females stemming from young twigs in groups of 1–3.[Kershner, Mathews, Nelson, and Spellenberg, National Wildlife Federation field Guide to Trees of North America, 2008, Chanticleer Press, Inc. p. 229]
Taxonomy
The current classification of the plant is as a distinct species.
Some botanists and the 1993 edition of
The Jepson Manual had classified it as
Juglans californica subsp.
hindsii, a
subspecies of
Juglans californica (Southern California black walnut).
[ Jepson Manual (1993) Treatment for Juglans californica subsp. hindsii — R. E. Sm.; Hickman, James C., ed. The Jepson Manual: Higher Plants of California. University of California Press. 1993.][ Calflora: " Juglans californica var. hindsii is not an active name in the Calflora species table." . accessed 10.1.2013]
Distribution and habitat
The historical range of
J. hindsii is from the San Joaquin Valley and Sacramento Valley to the inner northern California Coast Ranges and San Francisco Bay Area, in Northern California.
A 2020
IUCN assessment has extended this range: north to Oregon and south to Southern California, in areas of similar habitat type.
The northernmost pre-colonial
J. hindsii tree was located in Douglas County, Oregon, before it was blown over in November 2017. A
ring count determined the tree predated the arrival of settlers by approximately 100 years.
The Native Plant Society of Oregon has also documented multiple trees of pre-colonial age in Oregon's
Rogue Valley.
The tree grows in riparian woodlands, either in mono-species stands, or mixed with California oak species ( Quercus spp.) and Fremont cottonwood ( Populus fremontii) trees.
Conservation
Juglans hindsii was formerly assessed as Seriously Endangered on the California Native Plant Society Rare Plant Inventory. In a 2019 revision, the species was upgraded to common.
It is threatened by hybridization with orchard trees, urbanization, and habitat conversion to agriculture.
Cultivation
Juglans hindsii has been commercially important as a
rootstock for orchard stock of
Juglans regia (English walnut) trees all over the world. It is also used as a parent to the fast-growing Luther Burbank hybrid rootstock, commonly called "Paradox" (
Juglans hindsii x
Juglans regia).
[ UC Davis Nut Production: Walnut Rootstock & Scion Selection . Biology and Technology of Fruit & Nut Production . accessed 10.1.2013]
The Northern California walnut is cultivated by specialty California native plant nurseries. It is used as an ornamental tree in traditional and , and for , natural landscaping projects, and climate compatible xeriscaping. The tree is also planted in habitat restoration projects.
Pests
Juglans hindsii is infested by
Rhagoletis juglandis, commonly known as the walnut husk fly, which lays its eggs in the husks of walnut fruit.
R. juglandis infests other varieties of walnut trees as well, such as
J. regia (the English or Persian walnut),
J. rupestris (native to Arizona and Texas), and
J. hindsii (the California black walnut).
[Boyce, A.M. (December 1929). "The Walnut Husk Fly (Rhagoletis juglandis Cresson)". Journal of Economic Entomology. 22: 861–866.]
Allergenicity
It is a severe
allergen. Pollination typically occurs in spring.
Uses
The nut is edible.
The wood of J. hindsii is commonly called claro walnut by the lumber industry and woodworkers.[ Taunton.com: Finewood Working — "Claro walnut"] It is highly figured with a rich brown color and striking grain patterns, especially in the crotch areas, where large limbs meet the trunk.[ NW timber.com ] It is used in small quantities to make fine furniture and gun stocks, and sold as slabs to make large natural-top tables because of its durability, good working properties, and swirling iridescent figure.
Some confusion exists about the nature of claro walnut because J. hindsii is commonly used as the rootstock of orchard trees. The section below the original graft is claro walnut wood, while the section above is the lighter-colored English walnut. Some woodworkers take advantage of this by making the color change a feature of their work.[ Mcfaddenfurniture.com: 'armoire']
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"Some preliminary observations on the California black walnut ( Juglans californica)" — Anderson, E. N.; Fremontia: A Journal of the California Native Plant Society. January 2002.
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