Abstract
Several pecan cultivars for home and landscape plantings in the southeastern United States were identified in an evaluation of 23 cultivars and selections growing in southwest Alabama. Cultivars that appear to combine pest tolerance with good production and at least moderate quality, and thus are promising for landscape and home plantings, include Elliott, Sumner, Jackson, Melrose, and Jubilee.
Pecan (Carya illinoensis) trees are commonly planted in landscape plantings and in small home orchards in the southern United States with the dual goals of aesthetic appeal and production of nuts. Cultivars for such plantings are often selected based on name recognition (Stuart), nut size and thinness of shells (Mahan), early bearing (Shoshoni) or availability of trees due to popularity in commercial orchards (Desirable).
Performance of many cultivars selected is often poor in unsprayed landscape trees. Fungal diseases, particularly pecan scab (Cladosporium caryigenum), and other pests often are severely injurious when the cultivars are susceptible and the trees are unsprayed. Cultivars are often selected that produce poor quality pecans on older trees. This inferior quality frequently results when precocious cultivars, which bear nut crops early in the life of the tree, are selected. Early bearing is desirable when trees are young, and the leaf-to-nut ratio is high enough to maintain quality. In older trees, the leaf-to-nut ratio declines, and the precocious cultivars tend to overbear, alternately bear, and produce poor quality nuts (13). Also, cultivars are selected which are poorly adapted to an area, resulting in poor performance of a cultivar which may do well elsewhere (19).
Much can be done to improve performance of pecan trees in landscape plantings by careful selection of cultivars. The purpose of this paper is to report initial results of a pecan cultivar trial in southwest Alabama, to review applicable information on pecan cultivars for home plantings from other locations in the Southeast, and to offer suggestions on cultivars that show promise in the southeastern United States.
Materials and Methods
A pecan cultivar trial was planted in February, 1983, at the Alabama Agricultural Experiment Station’s Gulf Coast Substation near Fairhope in southwest Alabama. The Station is near the Gulf of Mexico and Mobile Bay in a warm, humid climate, averaging over 60 inches of rainfall annually and a growing season of 270 days.
The cultural management of the planting has been in accordance with standard commercial pecan recommendations, including spraying (4, 8). Since trees were sprayed, this initial report will indicate primarily the early yields, nut quality, budbreak and harvest dates of the cultivars, but will not evaluate pest tolerance, except as it may be reflected indirectly in yield and quality. Pest tolerance will be reviewed in the discussion and will be evaluated on these trees in a later report. General management included leaf and soil sampling annually in July, fertilizing in early-mid March according to recommendations based on sample results, pruning and training, and spraying with fungicides (3 sprays at 2-week intervals beginning at budbreak, followed by 4-7 additional sprays (depending on disease pressure) at 3 week intervals. Insect and mites were monitored according to Extension guidelines (8) and sprays applied as needed. Trees were irrigated as needed with drip irrigation. A weed-free strip in the tree row was maintained with herbicides, and grass in middles was kept closely mowed. Tree spacing was 40 ft. X 40 ft. (27 trees per acre). The planting was divided into two sections. The “main block” was in a randomized complete block design, with four 5-tree replications per cultivar. Fourteen cultivars (20 trees per cultivar) were being evaluated in the main test. In addition to the main block, an “observation block” had 9 additional cultivars planted in a completely randomized design with 3 single-tree replications per cultivar.
Information collected annually since the trees began bearing has been yield of nuts per tree, size and quality of nuts (percent #1, #2, #3, and reject kernels, total % edible kernel) (2). The harvest date was recorded when an estimated 50% of nuts could be readily shaken from the tree.
In 1988, budbreak data (date most active buds reached inner scale split stage) (5) and in 1989 relative order of budbreak and early spring growth was estimated by recording growth state (5) and length of new growth on April 17.
Results
Yield
A few cultivars were bearing nuts by 1986, their fourth growing season following planting, although none averaged as high as 1 lb of nuts per tree (Tables 1 and 2). Through age seven, Shoshoni produced the highest cumulative yield (37.1 lb), mostly from the 32 Ib/tree produced in 1989. Additional cultivars with cumulative yields of over 10 Ib/tree through the seventh season were Schley/Harris, Cape Fear, Kiowa, USDA 61-6-67, Jubilee, Davis, and Pioneer. Cultivars with less than 3 pounds per tree through the seventh season were USDA 56-6-148, Stuart, and Maramec (Table 1).
Mean yields per tree In years 4-7 of pecan cultivars or selections In the observation block at the Gulf Coast Substation.
Nut Quality and Size
Kernel quality is the primary consideration in determining value of pecans (2). Overall percentage kernel is important, and the grades of the kernels also dramatically affect price and quality. Seven cultivars, Forkert, Cape Fear, Kiowa, Jackson, Cheyenne, Melrose, and Elliott, had a percentage kernel of over 52% (Tables 3 and 4). The highest kernel grade is number one, which represents bright, thick kernels. Cultivars having over 40% number one kernels were Forkert, Cheyenne, Jackson, Elliott, and USDA 56-6-148. Less than 45% edible kernel, (relatively poor quality), was found with Stuart, Davis, Shoshoni, Owens, Candy, and Gloria Grande. The heaviest pecans, with inshell weight of over 9 g, were Jackson, USDA 56-6-148, Forkert, Kiowa, Choctaw, Maramec, and Gloria Grande. Candy and Elliott produced the lightest nuts, less than 6 g average weight.
Kernel grades and nut weight of pecan cultivars or selections In the main block at the Gulf Coast Substration.
Kernel grades and nut weight of pecan cultivars or selections in the observational block at the Gulf Coast Substation.
Budbreak and Harvest Dates
Early budbreak results in greater susceptibility to spring freezes, and cultivars with early budbreak should thus be avoided when planting in frost-prone sites. In 1988, budbreak occurred (Table 5) on April 1 or earlier, relatively early for pecans at this location, on Elliott, Candy, Cape Fear, Davis, Shoshoni, and USDA 61-6-67. Relatively late budbreak, after April 12, occurred on Jubilee, Forkert, Sur-prize, Sumner, Maramec, and Stuart.
Budbreak of pecan cultivars at the Gulf Coast Substation.
Harvest date influences value, since early season prices usually are highest (9). Cultivars with late harvest dates not only bring a lower price, but are at greater risk of early fall freeze damaging the nuts prior to shucksplit, especially when these cultivars are grown in colder climates. Cultivars with late harvest dates (Table 7), Nov. 1 or later, were Surprize, Pioneer, Gloria Grande, and 53-9-1. Very early harvest dates, before October 1, were recorded for Candy and Shoshoni.
Harvest dates In 1988-89 for pecan cultivars or selections in the observation block at the Gulf Coast Substation.
Discussion
The ability to produce high yields and high quality in well-managed and sprayed experimental plantings is required before pecan cultivars are recommended for home and commercial planting. However, this ability is not sufficient evidence that a cultivar will perform well when planted in a landscape planting with no spray program and minimal care. Numerous other sources are available which evaluate tolerance to scab and other pests (1, 3, 6, 7, 10, 15), very important criteria for trees in landscape plantings in the humid South. Also, researchers (12) have evaluated foliage retention or condition of foliage in late season—indirect measures of tolerance to aphids and other foliage pests. Review of this information, results obtained in this study, and lists of cultivars recommended for home plantings in the Southeast (15) suggest the following cultivars as promising in small plantings with minimal or no sprays. Data reported for the cultivars are from this study, where applicable, and from sources cited above.
Promising Pecan Cultivars for Home and Landscape Plantings
Davis
This cultivar was introduced in 1921 and is a prolific producer of mediocre quality pecans (16). Kernels may be dark and not well developed. Its good scab resistance and productivity with minimal care, plus its usefulness as a pollinator, are the reasons it is suggested for home and small plantings.
Pollination type I; harvest Oct. 13; 52 nuts/lb.; 41 % kernel; first yield of 1 lb. or more in year 6; good scab resistance; SE states recommending for home plantings: Alabama, Mississippi.
Elliott
This very scab-resistant cultivar is favored for home and commercial planting. The small, teardrop shaped nuts have high quality kernels. Elliott is also a favorite rootstock cultivar. Older trees tend to alternately bear. Very early budbreak makes it prone to late frost injury.
Pollination type II; harvest Oct. 7; 79 nuts/lb; 52% kernel; First yield of 1 lb. or more in year 7; very good scab resistance; SE states recommending for home planting: Alabama, Florida, Georgia, Louisiana, Mississippi, South Carolina.
Jackson
This cultivar was popular in the 1920s because it produces a very large nut with a high percent kernel. It has moderate scab resistance. Grower reports indicate that older trees do not consistently produce good yields.
Pollination type II; harvest Oct. 27; 41 nuts/lb.; 55% kernel; First yield of 1 lb. or more in year 7; good scab resistance; SE states recommending for home planting: Alabama, Louisiana, Mississippi.
Jubilee
On limited observations of older trees in South Alabama, this cultivar has produced good yields of large, thin-shelled nuts and has had excellent scab resistance. The tree grows vigorously. Kernel quality is moderate, and occasionally the long kernels do not develop completely all the way to the end. The large size, thin shells, and early harvest make it a good nut for inshell trade. It has not been grown long enough in test plantings for adequate evaluation, but appears from observations in grower’s orchards to have promise, especially for home plantings and for plantings receiving minimal sprays. Some late-season nut diseases have been observed on unsprayed trees.
Pollination type II; harvest Oct. 10; 55/lb.; 47% kernel; First yield of 1 lb. or more in year 7; very good scab resistance; SE states recommending for home planting: Alabama (trial).
Harvest dates In 1986-89 for pecan cultivars or selections In the main block at the Gulf Coast Substation.
Melrose
Released by the Louisiana Agricultural Experiment Station in 1979 (20), this cultivar produces a good quality pecan of adequate size. In addition to excellent scab resistance, it is reported to be more tolerant of zinc deficiency than are many other cultivars, and to retain foliage well.
Pollination type II; harvest Oct. 30; 69/lb; 53% kernel; First yield of 1 lb. or more in year 7; Very good scab resistance; SE states recommending for home planting: Alabama, Louisiana, Mississippi.
Moreland
We have not yet tested this cultivar in Alabama, but reports from Louisiana and Florida have been very favorable, resulting in its recent release (11). Moreland produces nuts of excellent quality and yields well. It has good to moderate scab resistance. It has not been found to have bunch or tumor and it has very little vein spot, liver spot, brown spot, or blotch diseases of leaves. It has no recorded shuck disease or severe black aphid damage. Leaf retention without sprays is quite good. It was officially released by the Louisiana Agricultural Experiment Station in 1989 but has been observed in test plantings for more than 40 years in Louisiana and Florida.
Pollination type II; harvest Oct. 15; 50 nuts/lb.; 56% kernel; First yield of 1 lb. or more in year 4; good scab resistance; SE states recommending for home planting: Alabama, Florida.
Owens
This cultivar has large, mediocre quality nuts and moderate production. The nuts are thick-shelled. The tree is scab resistant and has done well in Arkansas and Mississippi. It protandrous (Type 1) pollination habit and pest tolerance make it useful as a pollinator for home plantings, even though quality has been relatively poor.
Pollination type I; harvest Oct. 13; 54 nuts/lb.; 42% kernel; first yield of 1 lb. or more in year 7; Good scab resistance; SE states recommending for home planting: Alabama, Arkansas, Louisiana, Mississippi.
Sumner
This seedling cultivar from south Georgia has good nut size, precocity, and kernel percentage (17, 18). Scab resistance is good; harvest is late.
Pollination type II; harvest Oct. 24; 55/lb.; 53% kernel; First yield of 1 lb. or more in year 7; Good scab resistance; SE states recommending for home planting: Alabama, Florida, Georgia, Louisiana, South Carolina.
Surprize
The Surprize cultivar produces large nuts of moderate quality. The large nuts should be well-suited to inshell trade, even though the shell color is dark and grayish. Harvest is mid-season. This cultivar has moderate-good scab resistance. According to records maintained by Bill Underwood, a nurseryman and grower of this cultivar from Foley, Alabama, the trees have been consistently productive when given good care. Trees are strong and have withstood hurricanes well compared to other cultivars nearby. Kernels have bright color.
Pollination type I; harvest Oct. 17; 45/lb; 49% kernel; First yield of 1 lb. or more in year 7; Goodmoderate scab resistance; States recommending for home planting: Alabama (trial).
Footnotes
- © 1991, International Society of Arboriculture. All rights reserved.
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