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The Magic of Malus

James A. Chatfield and Erik.A. Draper

Associate Professor, Ohio State University Extension and
Assistant Professor, Ohio State University Extension

A paper from the Proceedings of the 12th Metropolitan Tree Improvement Alliance Conference (METRIA 12), Landscape Plant Symposium: Plant Development And Utilization, held in Asheville, NC, May 23-25, 2002, co-sponsored by the North Carolina State University, North Carolina Division of Forest Resources, USDA Forest Service Southern Region, North Carolina Landscape Association, North Carolina Association of Nurserymen, The Landscape Plant Development Center, The North American Branch of The Maple Society, and The International Ornamental Crabapple Society.


Introduction

The International Ornamental Crabapple Society (IOCS) was established in 1986 to evaluate ornamental crabapples (Malus taxa) for apple scab and other diseases and ornamental aesthetics as well as to promote crabapples for diverse environmental and landscape design situations. As part of the IOCS program a National Crabapple Evaluation Program was set up throughout the United States, with 17 replicated trial plots currently part of the program. This article details some of the key findings in the past decade at one of those plots, namely the Crablandia plots at the Secrest Arboretum at the Ohio Agricultural Research and Development Center of the Ohio State University in Wooster, Ohio

At Secrest Arboretum the Crablandia I plot consisted of 46 crabapple taxa with three single plant replicates planted in a completely randomized design. Crablandi I was established in 1983. The Crablandia II plot currently consists of 63 crabapple taxa with five single plant relpicates planted in a completely randomized design. Crablandia II was established in 1998. Three examples of data collected from these plots are presented and discussed below.

Aesthetic Evaluations

In both Crablandia I and Crablandia II, crabapples were evaluated monthly for aesthetic characteristics, from September 1992 through 2000 in Crablandia I and from 2000-2002 in Crablandia II. Detailed results of these aesthetic ratings are presented elsewhere (1-2), but from these monthly ratings full seasonal profiles have been developed for crabapple taxa in the plots, providing information on the full range of ornamental characteristics of crabapples, from flower and fruit to foliage and form. Following are a short list of fifteen diverse crabapple taxa with examples of short profiles developed from these aesthetic ratings. This is not a Top 15 list as such lists are too limiting, but rather these 15 examples reflect the diversity of crabapple taxa and the range of characteristics considered in the profiles.

Table 1. Aesthetic profiles of crabapples in Secrest Arboretum.

Crabapple Time of Effective Fruit Display1 Mature Tree Size Description Comments
'Adirondack' Late August to mid-December 12-15 feet Orange-red fruits, white flowers, narrow upright form.

Positives: One of the best crabapples for tight, columnar form; great autumn fruit/foliage combination; fruit ripens to a deep orange-red; fruit appears singular rather than clustered; annual consistent flowers are red-tinged.
Negatives: Somewhat slow to establish and grow; leafhoppers appaer to relish the foliage but no apparent harm from the feeding.
Diseases: No scab; some fireblight.

Malus baccata 'Jackii' Mid-August to late January 18-20 feet Maroon-red fruits, white flowers, broadly rounded form. Positives: Reliable flower display; large-glossy green leaves, by far the best foliage of any crabapple in the plot; outstanding fall contrast of yellow to rust colored leaves against attractive maroon-red fruit; bark has an orange cast.
Negatives: Relative sparsseness of fruit clusters and mediocre overall winter appearance.
Diseases: No scab.
'Bob White' Mid-October to late January 18-20 feet Gold-yellow fruits, white flowers, broadly rounded form. Positives: Persistent, small, firm fruits maturing mid-winter into striking orange-gold color; an excellent fruit color for fall and winter landscape; exceptional floral display of delicate white blossoms mixed with pinkish-red buds; overall one of the better yellow-fruiting selections of the plot.
Negatives: Fruit/floral display alternates yearly from profuse to sparse; lacks summer appeal due to inconspicuous green fruit color.
Diseases: No scab.
'Canary' Mid-August to mid-November 12-15 feet Yellow fruits, white flowers, upright open form. Positives: Bright yellow, tiny fruits hand in clusters along branches to accentuate open form; good autumnal fruit/foliage combination creates a blaze of yellow; cider brown fruit generates aesthetic interest in a fall with mild temperatures.
Negatives: Some early defoliation from scab in wet springs; fruit deteriorates rapidly to cider brown and falls off quickly after a few frosts.
Diseases: Minor leaf and trace of fruit scab.
'Candymint' Mid-July to late November 8-10 feet Red-purple fruits, pink flowers, low spreading form. M. sargentii selection. Positives: Graceful low spreading form; reliable fruit/floewr displays; burgundy-tinged leaves; new stems area deep burgundy; new foliage is striking, shiny wine-red.
Negatives: slow growing; fruit display is never overwhelming; dull summer leaf appearance.
Diseases: Trace of leaf scab.
'Excalibur' Mid-July to mid-December 8-10 feet Golden-yellow fruit, white flowers, dwarf rounded form. Positives: Consistent rounded tree form; tiny, small, shiny fruit is outstanding in the fall; fruit-lined branches create a striking specimen in the landscape; fruits mature to a shiny cider brown color but interest still retained.
Negatives: Flowers can be hidden by rapidly expanding foliage; fruit is hidden to the plant interior until leaves drop.
Diseases: No scab; apple mosaic virus noted.
'Holiday Gold' Late September to late March 15-18 feet Golden-yellow fruits, white flowers, open spreading form. Positives: one of the best new, yellow-fruited crabapples in the plot; annual flower show and fruit display is excellent; attractive cream-yellow frits mellow to golden yellow; rose blush accents yellow fruits; fruits hang in distinct clusters along branches.
Negatives: Tree form may become awkward due to fruit load.
Diseases: No scab; trace of fireblight.
'Louisa' Late July to mid-November 12-15 feet Lemon-gold fruits, pink flowers, true weeper form. Positives: Reliable annual bloom is a true pink; flower display is extraordinary, with pink cloud-like arrays; arching, graceful branches are upswept at ends; tree form is greatest asset; fruit mellows to a gold-orange with rose blush accent.
Negatives: Fruit set is consistently light and scattered, never dazzling.
Diseases: No scab.
'Manbeck's Weeper' Mid-September to mid-January 6-8 feet Cherry-red fruits, white flowers, spreading weeper form. Positives: Exquisite mix of pink buds opening to white blossoms; reliable annual fruit and flower displays; shiny red fruit accents the elegant, spreading weeper growth habit; new twig growth is an attractive red color.
Negatives: Pruning necessary to keep center from becoming too cluttered.
Diseases: Trace of scab.
'Molton Lava' Early September to mid-December 12-15 feet Red-orange fruits, white flowers, mounded spreading form. Positives: Consistent, profuse flower/fruit shows; fiery red fruits and yellowing fall foliage on cascading branch structure create a "molten lava" effect; excellent winter ratings dur to layered horizontal branching; feathery effect created by red pedicels after fruit drops;
Negatives: branches somewhat cluttered as tree matures; lacks summer appeal.
Diseases: Minor scab.
'Prairifire' Lae June to early December 15-18 feet Red-purple fruits, coral-pink flowers, open rounded form. Positives: Yearly spectacular bloom and fruit displays; blooms contrast with newly emerged red-tinted green foliage; firm purplish fruits slowly age to cherry-red; outstanding fall foliage colors range the spectrum from red to orange to apricot; attractive lenticel-speckled bark.
Negatives: Mediocre winter and early summer appearance.
Diseases: Trace of scab.
M. sargentii Mid-August to late October 6-8 feet Dark red fruits, white flowers, low spreading form.

Positives: greatest asset is attractive, low-spreading growth habig; petite snoy-white blossoms; effective firm fruits in late summer to early fall.
Negatives: Fruits deteriorate rapidly; shriveled raisin mummies persist into winter; some winter damage noted.
Diseases: No scab.

'Strawberry Parfait' Mid-August to mid-April 15-18 feet Red-cream fruits, pink flowers, open spreading form. Positives: Fruits age to deep red; yerly pink flowers borne on spur-lined branches; newly emerged foliage is a burgundy color; leaves mature to green with burgundy tint; unusual somewhat erratic upright-spreading growth habit; good fall color; fruits remain firm through late winter.
Negatives: Tenacious fruit mummies; unusual shape is not for every landscape.
Diseases: Trace of scab.
'Sugar Tyme' Late September to early April 15-18 feet Cherry-red fruits, white flowers, mounded spreading form. Positives: stunning sugar-white floral display from pale pink buds; showy, persistent firm fruiits through late wnter; good overall form; dense foliage.
Negatives: Mediocre appearance during summer before fruit colors; foliage appears off-color or chlorotic during mid to late summer; previous season's fruit drops all at once before bloom.
Diseases: Minor scab.

1Time of Effective Fruit Display derived from observations conductly monthly throughout the year. Effective fruit impact is defined as the period from the tree's fruit first contributes to tree aesthetics until the fruit is no longer ornamental.

Apple Scab At Secrest Arboretum in 2001

Apple scab (pathogen: Venturia inaequalis) is recognized by everyone as a key disease problem of ornamental crabapples, on some taxa resulting in significant foliage and fruit symptoms. Following is an example of one year of apple scab evaluations at Secrest Arboretum. Apple scab pressure was high at the Secrest Arboretum in 2001. Yet, even under this considerable disease pressure, 20 of the 63 taxa showed no evidence of apple scab in 2001 and a total of 30 never received a rating that exceeded 1 (no aesthetic impact) on any evaluation date. Twenty-one taxa received a rating of 3 or higher on at least one date in 2001, indicating substantial defoliation and aesthetic impact (Table 2).

Sixty three crabapple taxa were planted in 1997-1998 in Crablandia II at the Secrest Arboretum in a completely randomized design. There were five replicate plants for each taxa with the exception of ‘Brandywine', ‘Canary', ‘Dolgo', ‘Indian Magic', ‘King Arthur' and ‘Royal Scepter', for which there were four replicates, and ‘Hamlet', for which there were three. Plants were mulched with composted yard waste and irrigated as needed during the year of transplanting. Weeds were controlled with spot applications of glyphosate. On 13 June, 9 July, 2 August, and 19 September 2001, all trees were rated on a scale of 0-5, with 0 = no scab observed; 1 = less than 5% of leaves affected and no aesthetic impact; 2 = 5-20% of leaves affected, with some yellowing but little or no defoliation, moderate aesthetic impact; 3 = 20-50% of leaves affected, significant defoliation and/or leaf yellowing, substantial aesthetic impact; 4 = 50-80% of leaves affected, severe foliar discoloration and defoliation, severe aesthetic impact; and 5 = 80-100% of foliage affected, with 90-100% defoliation.

Apple scab ratings of crabapples at Secrest Arboretum for the 2001 season are presented in Table 2. Some key findings in 2001 included:

Table 2. Apple Scab at Secrest Arboretum in Wooster, Ohio in 2001.

Crabapple Taxon Sept. 19 August 2 July 9 June 13
'Adirondack' 0.00a 0.00a 0.00a 0.00a
'Bob White' 0.00a 0.00a 0.00a 0.00a
'Camelot' 0.00a 0.00a 0.00a 0.00a
'Callaway' 0.00a 0.00a 0.00a 0.00a
'Canterbury' 0.00a 0.00a 0.00a 0.00a
'Dolgo' 0.00a 0.00a 0.00a 0.00a
'Excalibur' 0.40ab 0.00a 0.00a 0.00a
'Firebird' 0.00a 0.00a 0.00a 0.00a
'Foxfire' 0.00a 0.00a 0.00a 0.00a
'Golden Raindrops' 0.00a 0.00a 0.00a 0.00a
'Guinevere' 0.00a 0.00a 0.00a 0.00a
'Hamlet' 0.00a 0.00a 0.00a 0.00a
'Holiday Gold' 0.20ab 0.00a 0.25ab 0.00a
'Jackii' 0.00a 0.00a 0.00a 0.00a
'King Arthur' 0.50ab 0.00a 0.00a 0.00a
'Lollipop' 0.00a 0.00a 0.00a 0.00a
'Louisa' 0.00a 0.00a 0.00a 0.00a
'Prairie Maid' 0.00a 0.00a 0.00a 0.00a
'Purple Prince' 0.00a 1.00b 0.50 0.00a
'Rawhide' 0.00a 0.00a 0.00a 0.00a
'Silver Moon' 0.00a 0.00a 0.00a 0.00a
'Sinai Fire' 0.00a 0.00a 0.60bcd 0.00a
'Strawberry Parfait' 0.00a 0.00a 0.00a 0.00a
'Tina' 0.00a 0.00a 0.00a 0.00a
M. sargentii 0.00a 0.00a 0.00a 0.00a
'Brandywine' 3.50mn 2.25de 1.60fg 2.00f
'Prairifire' 0.60bv 0.60b 0.80cde 0.00a
'Cinderella' 1.60ef 0.00a 1.00de 1.00bc
'Candymint' 0.20ab 0.30b 0.20ab 0.00a
'Coralburst' 2.00fgh 2.00cd 2.40ijk 1.40cde
'David' 1.00cd 1.00b 0.80de 0.75b
'Lancelot' 1.00cd 1.00b 0.40abc 0.00a
'Pink Princess' 1.40ef 1.00b 0.30bcd 0.00a
'Red Jewel' 0.60bc 0.80b 0.25a 0.00a
'Manbeck Weeper' 1.60ef 1.80c 1.20ef 1.00bc
M. floribunda 2.25ghi 2.00cd 1.80gh 1.80ef
'Professor Sprenger' 2.75jkl 2.75fg 1.00de 1.50de
'Mary Potter' 2.00fgh 2.40def 1.00de 1.80ef
'Sugar Tyme' 2.40ijk 2.00cd 1.80gh 1.40cde
'Donald Wyman' 2.75jkl 2.00cd 2.00ghi 3.00g
'Doubloons' 3.60nm 3.00gh 1.80gh 1.60def
'Molten Lava' 2.20ghi 2.40def 1.00de 1.00bc
'American Salute' 3.20lm 3.00gh 1.80gh 2.00f
'Canary' 3.00kl 3.00gh 1.80gh 2.00f
'Sentinel' 1.80efg 2.00cd 1.20ef 1.00bc
'Adams' 3.00kl 3.00gh 2.60ijk 2.60g
'Red Splendor' 2.60hij 2.60efg 1.60fg 1.00bc
'Royal Fountain' 3.00kl 2.80fgh 2.00ghi 2.00f
'Silver Drift' 3.00kl 2.40def 2.00ghi 2.00f
'Snowdrift' 4.20op 3.00gh 2.20hij 2.00f
'American Spirit' 3.20lm 3.00gh 3.00l 2.00f
'Soyal Scepter' 4.75q 3.20hi 2.00ghi 1.60def
'Red Jade' 2.20ghi 2.40def 1.00de 1.50de
'American Masterpiece' 4.80q 3.60ij 3.00l 2.00f
'Harvest Gold' 3.60nm 3.00gh 3.00l 2.00f
'Jewel Berry' 4.20op 3.20hi 3.00l 2.00f
'White Cascade' 4.80q 3.00gh 3.00l 2.00f
'Pink Satin' 4.60pq 4.00j 3.00l 2.00f
'Spring Snow' 4.00no 2.80fgh 2.00ghi 2.00f
'Weeping Candied Apple' 4.80q 4.00j 3.75m 3.00g
'American Triumph' 5.00q 3.40ij 2.60jk 2.00f
'Indian Magic' 4.75q 3.00gh 3.00l 1.50de
'Thunderchild' 3.00kl 2.60efg 1.80gh 1.20cd
     
Grand Mean 1.74 1.47 1.12 0.93
LSD 0.47 0.42 0.47 0.44

*0 = no scab observed.
1 = less than 5% of leaves affected and no aesthetic impact.
2 = 5-20% of leaves affected, with some yellowing but little or no defoliation, moderate aesthetic impact.
3 = 20-50% of leaves affected, significant defoliation and/or leaf yellowing, substantial aesthetic impact.
4 = 50-80% of leaves affected, severe foliar discoloration and defoliation, severe aesthetic impact.
5 = 80-100% of foliage affected, with 90-100% defoliation.

**Means with the same letter in a column are not significantly different (LSD test, p<0.05).

Apple Scab Evaluations From 1993-2000

One of the questions that is often asked of plant pathologists is to predict how bad a disease will be in an upcoming season. Plant pathologists usually hedge a great deal, though sometimes predictions are made based on how bad the disease was in a previous season, with inferences made relative to the future based, for example, on the probable amount of overwintering inoculum available for infection the next year. Relative to this and relative to apple scab in particular, the following graph illustrates the dangers of making such predictions. Table 3 indicates the amount of apple scab disease (based on the 0-5 scale described above) on the 46 crabapple taxa in Crablandia I from 1993-2000. The numbers are based on the August scab ratings in the plots, averaged over all of the taxa. Of particular note, see the years 1999 and 2000. In 1999 the relatively dry spring and summer weather in Wooster, Ohio resulted in the second lowest average scab in the plot over the 8 year period of the study. In 2000, the unusually wet spring and early summer weather in Wooster, Ohio resulted in the highest average scab in the plot in the 8 years of the study. To try to predict in the winter of 2000 how much scab would occur in the upcoming growing season, based on the low level of scab in 1999 would have been futile, since the then unknown upcoming environmental conditions in 2000 were the trump card.

Table 3. Apple Scab on Crabapples at Secrest Arboretum: 1993-2000

chart showing ratings of apple scab on crabapples

References

  1. Draper, E.A., Chatfield, J.A., Cochran, K.D. 2000. Crabapples at Secrest Arboretum-Aesthetics and More: A 2000 Update. Ornamental Plants Annual Reports and Research Reviews, 2000, pp.73-86.
  2. Chatfield, J.A., Draper, E.A., and K.D. Cochran. 1996. Comprehensive aestehtic evaluations of crabapples in Ohio: 1993-1995. Malus 10(1) 5-16.
  3. den Boer, John H. 1995. Blossom Times. Malus- The International Ornamental Crabapple Society Bulletin. 9(1). pp. 10-16.
  4. Fiala, Father John L. 1994. Flowering Crabapples - The Genus Malus. Timber Press, Portland Oregon.

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