Flora of North America species comparison

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Juglans hindsii

Juglans californica

Hinds' black walnut, northern California black walnut, northern California walnut

California black walnut, Southern California black walnut, Southern California walnut
Habit Trees, 6-23 m. Bark light or medium gray, split into smooth or ± scaly plates. Shrubs or small trees, to 6-9 m. Bark light or medium gray, divided into rough plates.
Twigs

with distal edge of leaf scar shallowly to deeply notched, not bordered by well-defined band of pubescence;

pith light brown.

with distal edge of leaf scar notched, often shallowly so, glabrescent or bordered by poorly defined velvety patch;

pith brown.
Leaves

22-45 cm;

petiole 3-8 cm.

15-24 cm;

petiole 2-5 cm.
Leaflets

13-21, narrowly triangular to lanceolate, symmetric or weakly falcate, (5.6-)7.3-13 × (1-)1.9-2.8 cm, margins serrate, apex acuminate;

surfaces abaxially glabrous or with sparse glands, sparse glands and few capitate-glandular hairs scattered along major veins, fasciculate hairs conspicuously tufted in axils of proximal veins, sometimes also on adjacent blade and edges of midrib, adaxially glabrous or with scattered scales, major veins glabrous or with sparse scattering of glands and few capitate-glandular hairs, without nonglandular hairs;

terminal leaflet well developed.

(9-)11-15(-17), usually narrowly oblong-elliptic to lance-elliptic, occasionally lanceolate, symmetric or weakly falcate, 4.3-9.5 × 1.6-2.6 cm, margins finely serrate, apex rounded to acute;

surfaces abaxially without tufts of hair in vein axils, abaxially and adaxially glabrous with scales but no hairs, main veins glandular, often sparsely so, leaflets without nonglandular hairs (except for multiradiate hairs early in season);

terminal leaflet well developed.
Fruits

1-2, globose, 3.5-5 cm;

nuts ovoid to ovoid-globose, 2.4-3.2 cm, smooth or nearly so or shallowly and indistinctly ridged or grooved.

1-3, globose, 2.1-3.5 cm, smooth, at first glandular, with scattered scales, soon glabrescent;

nuts depressed-globose, 1.8-2.2(-2.5) cm, shallowly grooved, surface between grooves smooth.
Terminal

buds ellipsoid to oblong, flattened, 6-8 mm.

buds ovoid to ellipsoid, somewhat flattened, 5-6 mm.
Staminate

catkins 6-15 cm;

stamens 20-40 per flower;

pollen sacs 1-1.4 mm.

catkins 5-14 cm;

stamens 15-35 per flower;

pollen sacs 0.6-1 mm.

Juglans hindsii

Juglans californica
Phenology Flowering spring (Apr–May). Flowering spring (Mar–May).
Habitat Along streams, sometimes on disturbed slopes Hillsides and canyons
Elevation 0-300 m (0-1000 ft) 30-900 m (100-3000 ft)
Distribution
from FNA
CA
[WildflowerSearch map]
[BONAP county map]
from FNA
CA
[WildflowerSearch map]
[BONAP county map]
Discussion

Of conservation concern.

Before 1850, Juglans hindsii was restricted to a few locations (J. R. Griffin and W. B. Critchfield 1972). It has been widely used as a rootstock for grafting J. regia and has been planted extensively in many parts of California for this purpose. It is now naturalized in many areas where it apparently did not occur before the introduction of commercial walnut growing. Possibly some of these naturalized populations are introgressed with J. nigra, since spontaneous hybridization between J. hindsii and J. nigra has been reported in areas where both species have been planted. These hybrids are difficult to distinguish from J. hindsii unless fruit are present. Currently most commercial walnut orchards use hybrid rootstocks, usually J. hindsii × J. regia (G. H. McGranahan and P. B. Catlin 1987).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Juglans californica is the most distinctive western walnut, but some care must be taken in identifying it. The distinctive leaflet shape of J. californica is occasionally replicated by early-season leaves of other species. Furthermore, J. californica is distinctive in lacking simple and fasciculate hairs on the leaves, but like most other walnuts, multiradiate hairs are normally present on the young vegetative growth (stems, petioles, and midribs) in the spring. The hairs are usually deciduous early in the growing season. They have short (0.1-0.2 mm), crisped rays and are never clustered or especially associated with vein axils. The fasciculate hairs found in all of our other species (except sometimes J. microcarpa) are persistent, have longer (0.3-0.4 mm), straight rays, and are concentrated in clusters abaxially in the axils of the main lateral veins.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 3. FNA vol. 3.
Parent taxa Juglandaceae > Juglans Juglandaceae > Juglans
Sibling taxa
J. californica, J. cinerea, J. major, J. microcarpa, J. nigra
J. cinerea, J. hindsii, J. major, J. microcarpa, J. nigra
Synonyms J. californica var. hindsii
Name authority Jepson ex R. E. Smith: Univ. Calif. Agric. Exp. Sta. Bull. 203: 27. (1909) S. Watson: Proc. Amer. Acad. Arts 10: 349. (1875)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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