Photo: Jerry Friedman — CC BY-SA 2.0 · source
Survives zone 6 through 9
Harvest calendar
Best planted in early spring after your last frost, or in fall before the ground freezes, depending on your climate.
Texas black walnut (little walnut) is the smallest of the cultivated walnut species, a drought-adapted small tree or large shrub of the dry rocky ravines and river bottoms of the southwestern United States and northern Mexico, grown more for its toughness, shelterbelt value and use as rootstock than for its small, thick-shelled nuts.
- Hardiness
- Zone 6–9
- Habit
- Tree
- Edible part
- Nut
- Ripens
- Sept–Oct
- Mature size
- Shrub or small tree 3–10 m — much the smallest walnut here, and the only one that is not a forest tree
- Light
- Full sun
- Soil pH
- 6.0–7.5 (near-neutral; lime-tolerant)
- Environment
- Arid
- Native range
- Native to the southwestern United States — southwestern and central Kansas, western Oklahoma, Texas, New Mexico and Arizona — south into northern Mexico (Chihuahua, Coahuila, Nuevo León). It grows on limestone stream banks, dry rocky ravines and hillsides, and within narrow riparian forests along rivers and creeks, often on shallow calcareous or alluvial soils.
- Status
- Wild
- Years to fruit
- 5–10 yrs
- Growth speed
- Described as fairly rapid once seedlings are established and growing well, though specific annual growth-rate figures are not documented in the sources available.
- Spacing
- 600 cm (236 in) apart — about 36 m² (388 sq ft) per plant
- Leaf shape
- Pinnately compound leaves 9–23 cm long bearing 17–23 narrow, linear-lanceolate, curved leaflets, each 3–9 cm long and 1–2.5 cm wide.
- Root system
- Develops a deep taproot and is intolerant of root disturbance once established; adapted to low soil-moisture sites, but highly susceptible to root or crown rot if the soil is periodically flooded.
- Fruit description
- A globular fruit 2.8–3.2 cm in diameter with a thin, brown, hairy husk and a thick, hard shell — the smallest nut in the genus. The nutmeat is described as nutritious and of high quality, though the small size and thick shell make extraction laborious.
- Propagation
- Propagated from seed, which has a dormant embryo and a hard seed coat like other North American walnuts — dormancy is broken by chilling at 3–5°C for 90–120 days. Nurseries either sow seed in fall shortly after harvest or pre-chill it over winter in moist sand under soil mulch (with rodent-proof screening and fungicide protection), then sow pre-chilled seed in spring; germination around 50% is typical, and nicking the shell can speed things up. It has also been used as rootstock in developing non-native (hybrid) walnut cultivars.
- Pollination
- Monoecious but HETERODICHOGAMOUS — a 2nd cultivar of the opposite type greatly improves set
The edible parts listed above are a starting point, not a field guide. Identify a plant with certainty — ideally against a local authority — before eating any part of it, and read the full disclaimer. Spotted something wrong? Report it.
Growing guide
Fertilizing. A light feeder that usually needs no more than a restrained, once-a-year feeding — a small amount of balanced tree fertilizer or compost applied in early spring is enough for normal growth. Heavy fertilization is unnecessary and can push soft growth on this naturally drought-tolerant species; avoid feeding in late summer or fall so new growth can harden off before winter.
How it spreads. A small tree with single or multiple trunks and spreading low branches — non-suckering, spreading only by seed dispersal rather than by root suckers.
Growing tips. The smallest and most drought-tolerant of the cultivated walnuts, adapted to sites with much more limited soil moisture than other Juglans will tolerate. It is less susceptible to walnut anthracnose than black walnut, but is highly susceptible to root or crown rot where soil is periodically flooded. Trees are slow to bear — around 15–20 years from seed — with irregular fruiting at 2–3 year intervals. Juglone is present as in all walnuts, but essentially all allelopathy research uses J. nigra as its source material, implying comparatively lower juglone output in this smaller species, though this has not been rigorously quantified.
Companion planting. Like other walnuts, likely produces some juglone (a root-zone compound toxic to sensitive plants like apples and blueberries), though this species hasn't been specifically studied for it — black walnut's spacing precautions are a reasonable default.
Grow journal
Sign in to keep a dated log of when you planted, bloomed and harvested this plant.