Pecans (Carya illinoensis)

How well established is this crop?

Initial trial plantings of these crops may have been done. There is little information on plant suitability to the region and no current information on markets, commercial returns or current research. This is a new crop.

Background

Pecan is considered one of the most valuable nut species. The word pecan, means a nut too hard to crack by hand. Its scientific name, Carya illinoensis is from karyon (an ancient Greek name for nut) and a latinised version of Illinios, meaning the nut that grew in the territory occupied by the Illinois Indian tribe. This member of the Hickory family originated in North America but Pecan trees have been growing in New Zealand for more than 100 years.

Climate

Pecans grow well through most of the North Island and the top of the South Island, though cultivars are available to suit most other climates. Some of the North American cultivars are now grown as far north as Ontario as well as in Hawaii.

Winter Chilling and Frosts

Approximately 150 to 210 frost free days are needed through the growing season for nut production. Temperatures need to be warm enough to sustain an adequate growing season, with a chill spell during the winter dormancy. The pecan can stand heavy frosts when dormant, but late frosts prevent fruit setting and even kill fruit that has set. Thus a site with good air-drainage and a frost free period from the initial growth stage in spring until the nuts mature in autumn is required. If this cannot be assured, some form of frost potection is advised.

The pecan grows best where average summer temperatures are within the 25 degrees C to 30 degrees C range with little difference between night and day temperatures. It has a definite cold requirement: 750 hours below 7 degrees C has been suggested in overseas literature, but again there are definite clonal differences in this respect.

Rainfall and Irrigation

The required rainfall and irrigation requirement is between 750mm - 2000mm. Water is needed to initiate nut growth , increase size and to prevent nuts drying out and dropping prematurely.

Wind

If grown in windy conditions large branches are often blown out. Therefore pecans should be grown in sheltered sites.

Soil

Pecans are native to river and creek bottoms, the soils of which are deep, fertile, well-drained and have substantial water holding capacity. Pecans planted on shallow soils will have trouble developing to their full potential.

Fertility

Pecans require relatively high amounts of the major macro and micro nutrients. nutrients. Foliage and soil tests should be used along with expert analysis of the results to keep the trees growing well.

Weed Control

Weed control in pecan blocks tends to be quite straightforward. When young trees are planted, plastic spray-guards are put around the trunks. This prevents rabbit damage and allows herbicides to be sprayed right up to the tree. Weeds growing up inside these guards are removed by hand. As the trees mature the bark on the trunk hardens and herbicides can be sprayed on them with no damage to the tree.

Varieties

The only indication of cultivars performing well are Mohawk in Gisborne and Apache doing reasonably well in Nelson. However considering the short time this assessment has been going on, nothing clear cut is indicated. A sensible approach is to try the Northern cultivars for Otago as a starting point.

Some growers are also raising trees from seed.This method works if you are growing for timber but will give uneven nut yields.

Pests and Diseases

We have few pests to harm pecans in NZ so spray programmes can be kept to a minimum unless a problem is encountered. Quarantine, so far, has kept problems out. Growers should therefore report anything suspicious to MAF.

Other problems are wind (broken branches), possums, borers, shield bugs, bronze beetles and cicadas. Eastern cultivars are adapted to more humid conditions and are less susceptible to Pecan scab (Fusicladium effustum) . While it is not established in this country the importance of trying to establish pecans without the disease must be stressed. Pecan scab is characterised by irregular brown to black spots on the leaves and circular spots on the nuts.

Layout

Pecan trees have a very long life span and can attain a great size. However to increase their profitability in early years interplanting is advisable. Initial planting may be on the square system 7.5 m x 7.5 m or 175 trees per hectare. Alternate diagonal rows are removed at the first thinning and then alternate rows for the second thinning. The remaining trees would be at 15 m x 15 m spacings. Tree removal should be done when sunlight in the orchard floor does not reach 30-40 % in the middle of the day (Malstrom, et al. 1982). Immediately after planting trees should receive a thorough soaking with water and again a week later. Over irrigation of young tree can result in rotting of the roots. An occasional check is necessary to see that no growth develops from below the scion. Remove it if it does. Animals should not be allowed in the paddock for at least three years after planting unless the trees are protected. Where it is intended to graze stock the stem should be trained to 2 m free of side branches.

General Management

Prepare planting site by digging holes 45-60cm wide and 60-90cm deep. This is large enough for most seedlings. Care should be taken to spread the roots so they are not matted together. All broken roots should be trimmed. Add soil in small amounts at a time while carefully spreading other roots until the hole is filled. Water the soil well to remove air pockets and firm the soil around the root system. Do not fertilise at planting time. Pecan mainly makes subterranean growth during its first year. If conditions are at all harsh, newspaper etc can be tied to the tree about 15cm from the surface of the soil but leaving the top protruding. This cover is needed only for the first year. This is important as the tree when planted has only enough sap to keep it alive. If the tree is not covered it can dry out during the 4-6 months it takes to establish. This in turn can lead to the stock (of no commercial value) growing and graft dying. This has been experienced in the Gisborne area.

Pecan flowers from September to November about a week after the leaves have started to open. The nuts mature from March to April and fall March to June.

Harvest

Budded or grafted trees start bearing about 4-7 years after planting. Some trees are alternate bearing. A potential yield of around 3 tonnes per hectare could be expected.

Pecan nuts have smooth brown mottled shells with a greater proportion of kernel than walnut, and thinner partitions separating the two halves of the kernel. Their shape varies from long cylindrical with a pointed apex, to short and roundish, with many intermediate forms. Nuts should be symmetrical, large and with good kernel. Kernel percentage varies but an average of 40% is considered satisfactory. The kernel has a 78% fat content at 6200 calories per kilogram (compared with chestnuts at 4-5% fat and 2400 calories per kg).

Taking care of the nuts when they fall is important. Pecans last a long time, particularly when frozen and can hold their freshness for up to two years. Store shelled or unshelled. Nuts in shell retain quality longer than shelled and large pieces store longer than tiny pieces.

Equipment

Basic gardening equipment such as a mower, weed sprayer etc is all that is needed for most plantings.

Returns

Pecans are a sought after nut and increasingly so in New Zealand. They are obviously a favourite with Americans but lesser known to other nations The USA production is increasing annually. Australians must have a greater appreciation for them as they are now producing their own. New Zealand is a long way from producing enough nuts to make any impact, and there are not many plantings with significant yields. The greatest concern with local production is the small size of the nuts. This should be improved when more suitabl cultivars have been identified although it could be a young tree phenomenon and also with climatic changes this may alter.

Apart from nut production, pecan timber could be another choice for pecans, It is a valuable timber and good quality in this country. Seedlings would be relatively easy to train for a straight trunk and this could minimise branch breakage. Twenty-five years has been mentioned as a possible timber harvest which easily matches pine growth. The faster hardwoods grow the better the timber quality. Pecan yields hard strong timber used for furniture, flooring and tool handles. Also excellent source of firewood and BBQ or food smoking.

Contacts

Owen Long 28 Highland Rd, Mt Aibert, Auckland
Paul Dodgshun Ruaweka , Private Bag 7213, Gisborne
Alison Ellett, Wharepapa, RD 2, Helensville