Black Walnut |
| General |
| Common Name | Black Walnut |
| Latin Name | Juglans nigra |
| Category | Nuts |
| Family | Walnut |
| Variety | |
| Visual Traits |
| Flower | yellow-green, monoecious, late May-early June at leaf-out |
| Foliage/Fall leaf color | golden yellow, early to mid-September |
| Fruit / Nut | fruit ripens Sep-Oct; persistent through leaf fall |
| Height | 75-100ft |
| Other valued traits | fine furniture |
| Spread | 75-100ft |
| Cultivation |
| Cultivation and Mulching | requires weed management 2-3y |
| Field spacing / planting depth | 50x50ft spacing optimal for nut production |
| Grafting | inlay graft |
| Pollination | flowers of both sexes do not usually mature simultaneously on single tree; may set self-fertilzed seeds |
| Propagation method | seed, grafting and budding, container |
| Pruning | prune lateral branches, early spring; sprouts after disturbance; some bole sprouting in response to release; nut v. timber production objectives define different tree forms and pruning practice |
| Seed treatment and storage | cold stratification 90-120days |
| Seedling treatment | seedlings smaller than 3/16in caliper (at 1 |
| Sowing seed | germinates early spring during first or second season |
| Transplant | machine or hand |
| Critters |
| Insect and invertebrate pests | walnut caterpillar (Datana integerrima), fall webworm (Hyphantria cunea), ambrosia beetle (Xylosandrus germanus), flatheaded apple tree borer (Chrysobothris femorata), walnut curculio (Conotrachelus retentus), walnut shoot moth (Acrobasis demotella) |
| Pathogens | fungi: (Phytophthora citricola) and (Cylindrocladium spp.), walnut anthracnose (Gnomonia leptostyla), (Cristulariella pryamidalis), (Mycosphaerella juglandis), and (Nectria gallegena) |
| Toxicity | juglone concentrated in roots and nut husks inhibits associated vegetation |
| Soils |
| Compaction (tolerance) | intermediate |
| Fertility / quality | rich, fertile |
| Minerals | associated with limestone |
| Moisture and drainage | deep, moist, well-drained; suppressed on dry ridge sites; moderately flood tolerant |
| pH | 4.6-8.2 |
| Salt tolerance | intolerant |
| Soils and topography | coves, well-drained bottomlands; alluvial soils |
| Texture | prefers sandy loam to silty loams, silty clay loams |
| Growth Pattern |
| Good seed crop interval (fruit load) | twice in 5y; flowering habit may be strongly influenced through cultural practices like pruning, irrigation, and pest control |
| Growth rate | fast, surpasses oaks |
| Longevity | long |
| Root habit | taproot or strong lateral roots, depending on soil |
| Seed-bearing age /max production | 10y / 30y |
| Habitat and Climate |
| Exposure | performs best on lower north or east-facing slopes |
| Fire tolerance | readily sprouts following disturbance |
| Frost-free days (FFD) | 170 |
| Growing degree days (GDD) | 140-280 |
| Hardiness Zone | Zones 4-9 |
| Native Range | Central and Eastern United States, Southeastern Canada |
| Rainfall / humidity | 35in |
| Wind / ice / frost susceptibility | susceptible to early fall and late spring frosts |
| Light |
| Light recommendation | full sun, woodland edges |
| Shade tolerance | intolerant, esp at pole stage |
| Vegetation Associations |
| Competitive ability | must be dominant or codominant; allelopathic; responds well to release of at least 3/4 of crown |
| Indicator species and associated forest | mixed mesophytic |
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