Pecan nut

Family

Juglandaceae

Habit

Tree

Height

40 m

Spread

20 m

Growth

medium

Lifespan

1000 years

First yield

after 6 years

Full yield

after 30 years

Productive years

80 years

Yield per plant

up to 55 kg a year

Yield in cultivation

up to 1 t/ha

Energy yield

700 kcal per m² a year

Hardiness

zone 5–10

Shade tolerance

full sun

Soil

Sand, Silt, Loam

Soil moisture

semi-dry – very wet

pH

4.5 – 7

Synonyms

Carya pecan, Juglans illinoensis

Times apply to the northern hemisphere in a temperate climate and shift with altitude and cultivar.

Edible: Pecans are drupes with a fleshy, inedible green husk that splits along four preformed seams as the fruit ripens. The nut itself is elongated and cylindrical, pointed at one end, thinner-shelled than a walnut and closer in appearance to a large hazelnut; 60 to 175 nuts make a kilogram. The kernel is about 71 per cent fat, with 15 per cent carbohydrate and 9.2 per cent protein, plus generous potassium, phosphorus, magnesium and calcium. It tastes milder and sweeter than walnut and carries far less tannin; it is eaten raw, chopped over fruit salads and desserts, or baked into pies and ice cream. The high fat content means kernels turn rancid quickly — store them cool and airtight.

Medicinal: Bark (astringent) - decoction (for tuberculosis); Leaves (astringent) - powdered (rubbed on the skin to treat skin fungus).

Other uses: Pecan timber is coarse-grained, hard and heavy but also brittle and not especially strong — it is rated below the other hickories, which are prized for tool handles and bow staves. It is used for wagon parts, farm implements and above all as firewood; in the southern United States hickory chips are the standard for smoking meat. More interesting for garden planning is the tree's role as structure: the broad, open crown lets enough light through for underplanting, and the deep taproot leaves room for shallow-rooted neighbours. The pinnate foliage breaks down slowly and yields plenty of autumn mulch. The empty shells make a durable, slowly rotting path covering.

Site: In Central Europe the pecan is a borderline case — it needs 180 to 220 frost-free days to fill the kernel, and that is exactly where most locations fail. It is worth planting only in the warmest wine-growing districts; elsewhere it stays a handsome but nutless tree. It wants light to medium, deep soils on the acid side, between pH 5.5 and 6.0, and forms a pronounced taproot that makes transplanting difficult — plant small rather than buying large. At 20 to 30 metres tall and 10 to 15 wide it is a tree for open ground, not for a domestic garden. Like all walnut relatives it produces juglone, though far less than black walnut; even so, sensitive neighbours such as tomato, pepper and apple are better kept out from under the canopy. The trees are functionally dioecious because pollen shed and stigma receptivity are offset in time: a second tree of a different cultivar is a precondition for any crop. Care: The wood is damaged below -20 °C, so young trees need trunk protection for the first few years and a position free of late frost. Rain and high humidity encourage fungal attack; an open, well-ventilated site is the most effective guard against pecan scab. Prune little and early — build a clean crown in the first years, then take only dead wood and competing leaders. Young trees need even watering; older ones ride out dry spells on their taproot. First nuts fall after four to six years, and a full crop is not to be expected before the tenth season. Harvest in October by shaking, once the green husks split. In its homeland the pecan weevil hollows out the kernels; in Europe it is so far not an issue.

Seedling pecans vary widely in yield and nut quality and take considerably longer to bear — seedlings therefore serve mainly as rootstocks. The nuts must be stratified moist and cool and must not dry out between harvest and sowing. True-to-type trees come from scion grafting with one-year-old shoots in February or March, usually by whip or cleft graft; in the United States trees are also field-grafted onto established seedlings and patch-budded as with walnut. For Central European conditions, grafts of the North American 'Northern pecan' cultivars are the most promising choice because they cope with a shorter growing season; the classic southern cultivars do not ripen here.

The pecan is wind-pollinated. Its long male catkins shed pollen in abundance but offer no nectar and no forage that bees will work; the USDA report on crop pollination accordingly rates it as unattractive in every bee column. As a North American newcomer it also has no caterpillar or beetle species tied to it in Central Europe. Its value to wildlife lies entirely in size and fruit: a mature tree of 20 to 30 metres with a broad, open crown is a perch, a nest tree and in time a cavity tree, and the nuts are taken and carried off by squirrels, jays and other corvids. In its homeland a substantial part of the forest fauna lives off hickory mast years; in a European garden what remains of that is mostly competition for the harvest.

Notable: needs 180-220 frost-free days, productive in Central Europe only in the warmest sites; wood damaged below -20°C; requires pH 5.5-6.0; functionally dioecious (dichogamous) -> second cultivar essential; first crop after 4-6 yrs, full yield from 10 yrs; 60-175 nuts/kg; kernel ~71% fat+15% carbohydrate+9.2% protein; orchard spacing 12x12 to 17x17m; choose 'Northern pecan' cultivars for Central Europe; kernels turn rancid fast;

Southern North America: the Mississippi valley from Illinois and Iowa south to Louisiana, and west through Texas into northern Mexico. Its centre is the valley of the Mississippi and its tributaries, to which the epithet illinoinensis refers. The pecan is grown chiefly in the southern United States, which produce some 95,000 tonnes a year; total US production runs between 120,000 and 140,000 tonnes. Other producing countries are Mexico, Australia, Israel, southern China, India and, on a small scale, Sicily and Spain. In Central Europe it goes no further than enthusiast planting in the warmest districts.

Moist, fertile floodplain soils along rivers and creeks, often in periodically flooded bottomland hardwood forest together with American elm, ash, cottonwood and overcup oak. The pecan is a classic floodplain tree: it tolerates temporary inundation but demands deep, well-aerated soil on the slightly acid side, and forms a strong taproot that carries it through summer drought. The climate of its range is hot with summer rainfall and a long growing season of 180 to 220 days — the short Central European season is the real reason the tree grows here but rarely fills its kernels.