Little Walnut Juglans microcarpa
Little Walnut is a perennial tree native to the lower 48 states. It grows to 20 ft and blooms Apr in part shade – shade, with black fruit. A keystone plant for native insects and the food web.
More about this plant
Juglans microcarpa, known also as the little walnut, Texas walnut, Texas black walnut or little black walnut, is a large shrub or small tree which grows wild along streams and ravines in Texas, New Mexico, Oklahoma, and Kansas, and the northernmost states of Mexico. It produces nuts with a width of 1/2—3/4 in. The pinnately compound leaves bear 7—25 untoothed to finely-toothed leaflets, each 1/4—1/2 in wide. It is found at elevations ranging from 700 ft to 6700 ft. Wikipedia →
Growing & care
USDA PLANTS · TRY- Sun
- Part shade – shade
- Soil & moisture
- Medium moisture
- Soil pH
- 5.5–6.9
- Fertility need
- Low
- Adapts to
- Coarse (sandy), Medium (loam), Fine (clay)
- Hardiness
- USDA zone 7+
- Height
- 20 ft
- Mature width
- ~ 12 ft wide DERIVED derived estimate — open-grown crown allometry (height × growth-form ratio); not a measurement
- Spacing
- 7–21 ft apart from USDA planting density
- Spread
- None — clumping
- Growth rate
- Slow
- Growth form
- Single stem
- Lifespan
- Perennial · long-lived
- Foliage
- Broadleaf · coarse texture
- Active growth
- Spring & summer
- Fruit
- Black persists into winter
- Propagate by
- Seed, Bare root, Container
- Seed starting
- Needs cold stratification a cold-moist spell before it germinates
- Seeds ripen
- Summer seed-collection / harvest window
- In the trade
- Routinely available
- Resprouts if cut
- No
Sow timing keys off your local last- and first-frost dates.
Wildlife & pollinators
How pollinator value is scored →❧ Caterpillar hosts ~129 caterpillar species
Juglans supports ~129 caterpillar species.
Native butterfly & moth caterpillars are the base of the terrestrial food web — most songbirds rear their young almost entirely on them. As a host for native Lepidoptera this is an exceptional genus.
Recorded feeding on Juglans in North America, including:
+ 8 more species → ↑ show fewer
✦ Bees 1 bee visitor
1 native & managed bee species is documented visiting Little Walnut :
Related plants
More Juglans →
How we know this (3) Methods & honest limits
A recorded categorical fact: each species is tagged C3 (standard), C4 (heat/water-efficient) or CAM (succulent, night-time CO₂ uptake) — or a facultative combination. We only show a trait card for the noteworthy C4/CAM cases; C3 is the unremarkable majority, kept in the data but not surfaced as a card.
We take the plant’s U.S. county range and look up each county’s long-term climate, then summarise: native rainfall = the median annual rainfall across its counties; heat tolerance = the warm end (90th percentile) of average temperature across its range (mirroring how our cold-hardiness floor uses an extreme). Counties + medians blunt the roadside/observer bias that makes point-level climate unreliable. Needs at least five placeable counties.
Honest limits: A realized, sampling-biased niche (where it has been recorded, not its physiological optimum), and county climate is coarse — large Western counties span deserts and mountains. Derived guide, never a measured fact.
For woody plants that have a height but no measured crown, we estimate width = height × a crown-to-height ratio fit for that plant’s form (conifers narrower than broadleaf trees, shrubs widest), calibrated on our measured open-grown crowns and capped at the largest one ever measured. A measured crown always wins; herbaceous plants get nothing (no anchor).
Honest limits: A coarse class-median estimate for garden-scale spacing, not a measurement; woody single/multi-stem forms only.
Sources for this entry (34) Open & cited
Cite this page Open data, please attribute
PlantKey’s data is open under CC BY-SA 4.0 — free to reuse and adapt, with attribution and the same licence. Photos keep their own per-image licence + credit (see Sources above).
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