Carya illinoinensis was the original spelling Wangenheim used throughout his publication of this name, and there is no valid basis for accepting the deviant spelling 'illinoensis' that is often used[].

Common Name: Pecan

General Information

Carya illinoinensis is a deciduous tree that can grow up to 50 metres tall with mature trees developing a huge canopy with broadly arching branches[].
Supplying the pecan nut of commerce, this species has a long history of traditional use for food, medicines and as a source of wood. It is widely cultivated for its seed, which is used for food and as a source of oil.
Carya illinoinensis has a large geographic range and is abundant within that range. It is also grown on a large scale for its edible seeds. There are no major threats to the wild species The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2013)[].

Known Hazards

None known

Botanical References

, ,

Range

Southern and central N. America - Kansas, Iowa, Illinois and Indiana, south to southwest Mexico, Texas and Mississippi

Habitat

Rich moist soils of bottomlands[], especially along the sides of streams[].

Properties

Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Deciduous Tree
Height	30.00 m
Growth Rate	Medium
Pollinators	wind
Self-fertile	Yes
Cultivation Status	Cultivated, Wild

Cultivation Details

Carya illinoinensis grows in a humid climate; the minimum average annual rainfall approximates 760mm and the maximum reaches 2,010mm, of which at least 510mm falls during the growing season. Annual snowfall varies from zero to 50cm. Mean summer temperatures range as high as 27°c, with extremes of 41 - 46°c. Average winter temperatures vary from 10° to -1°c, with extremes from minus 18° to plus 29°c[]. Dormant trees are said to be hardy to about -12°c, the same report also says that they are hardy to zone 5[], which would experience considerably lower temperatures than this. Trees are probably much hardier when grown in areas with hot summers. In the wild, trees grow best in areas where summer temperatures average 24 - 30°c and the humidity is high[].
Prefers a deep moisture-retentive loam in a sunny sheltered position, requiring a good summer for best development[, , , ]. The wild plant grows on rich, well drained, alluvial soils often near river bottoms but not in localities experiencing prolonged flooding[]. Tolerates a pH in the range 4.5 to 8.3. Trees are fairly fast growing[].
Trees do not grow very well in cool maritime climates, requiring hotter summers than are normally experienced in order to fruit and fully ripen their wood[]. However, a tree at Cambridge botanical gardens was 20 metres tall in 1985.
Often cultivated for its edible seed, there are some named varieties[]. Trees come into bearing when about 20 years old, the best period of production being between the ages of 75 to 225 years old[]. Mature trees regularly give yields of 225 kilos, whilst yields of 450 kilos have been recorded[]. A number of cultivars have been developed in N. America that succeed quite far north in that country[]. These cultivars include:-
'Carlson 3'. Early maturing, it is being trialled in Canada[].
'Devore'. An early fruiting form with small nuts that have an excellent flavour[].
'Gibson'. Precocious, protandrous, the nuts are of medium size with a good flavour[].
'Green Island'. Amongst the hardiest of cultivars, it has been selected for nut size, flavour and productivity[].
'Mullahy'. Hardy, precocious and very productive, it has ripened in Ontario[]. Nuts are fairly large with an excellent flavour.
'Voiles 2'. Usually ripens as far north as Ontario and New York[].
The wind-blown pollen is a significant cause of hay fever in the Unitd States[].
This species is the State Tree of Texas[].
Plants are strongly tap-rooted and should be planted in their permanent positions as soon as possible[, ]. Sowing in situ would be the best method so long as the seed could be protected from mice[, ].
Plants in this genus are notably resistant to honey fungus[].
Most species in this genus have quite a wide range of distribution and, in order to find trees more suited to this country, seed from the most appropriate provenances should be sought[]. Most trees growing in Britain at present tend to only produce good seed after hot summers[].
Trees are self-fertile but larger crops of better quality seeds are produced if cross-pollination takes place[].

Edible Uses

Seed - raw or cooked[, ]. Sweet and delicious, they make an excellent dessert and are also often added to ice cream, used in cakes, bread etc[, ]. A milk can be made from the seed and is used to thicken soups, season corn cakes, hominy etc[]. The seed is up to 4cm long and is produced in clusters of 3 -11[, ]. The seed ripens in late autumn and, when stored in its shell in a cool place, will keep for at least 6 months[].

An edible oil is obtained from the seed[, ].

The leaves are said to be used as a tea[, ].

Medicinal

The bark and leaves are astringent[]. A decoction of the bark has been used to treat TB[].

The pulverized leaves have been rubbed on the skin to treat ringworm[].

Agroforestry Uses:

Trees are late coming into leaf (usually in late spring to early summer) and they lose their leaves early in the autumn (usually in October)[]. Whilst in leaf they cast a heavy shade. These factors combine to make the trees eminently suitable for a mixed woodland planting with shrubs and other trees beneath them[].

Other Uses

Wood - coarse-grained, hard, heavy, brittle, not strong. It weighs 45 lb. per cubic foot. It is not as valuable a timber as other members of this genus and is used mainly for fuel and occasionally to make wagons and agricultural implements[, , , ]. Demand for the wood has steadily increased in recent decades and it is used for various different applications including furniture, cabinetry, panelling, pallets, and veneer. The wood has good machining properties, resembling those of true hickories[].

Propagation

Seed - requires a period of cold stratification. It is best sown in a cold frame as soon as it is ripe[]. Stored seed should be kept moist (but not wet) prior to sowing and should be sown in a cold frame as soon as possible[]. Where possible, sow 1 or 2 seeds only in each deep pot and thin to the best seedling. If you need to transplant the seedlings, then do this as soon as they are large enough to handle, once more using deep pots to accommodate the tap root. Put the plants into their permanent positions as soon as possible, preferably in their first summer, and give them some protection from the cold for at least the first winter[, ]. Seed can also be sown in situ so long as protection is given from mice etc and the seed is given some protection from cold[] (a plastic bottle with the top and bottom removed and a wire mesh top fitted to keep the mice out is ideal)