Erik A. Draper
James A. Chatfield
Kenneth D. Cochran
Peter W. Bristol
David E. Allen
Forty-four crabapples (Malus spp.) were rated for five years for aesthetic qualities, flower duration, season of fruit effectiveness, tree form, and disease characteristics. Fourteen additional crabapple selections were evaluated under these same parameters in 1997. Overall profiles of these crabapples developed from these ratings are presented in this paper.
Crabapples are often thought of and used mainly as a flowering tree, creating a welcome relief of blossoms in spring landscapes. However, this ornamental tree offers many seasonal impacts beyond the "flowering tree" label. Often ignored are aesthetic qualities like ornamental fruit effect and changing fruit color, leaf shape and fall color, bark exfoliation and tree form. The purpose of this on-going study is to develop an accurate year-round profile of commonly used ornamental crabapples. This profile benefits commercial landscapers, nursery operators, landscape architects, and homeowners alike in their selection of a particular crabapple for a specific landscape use. Understanding strengths and weaknesses of each crabapple increases the likelihood of complementing the landscape rather than causing a detraction.
Forty-four crabapples at Secrest Arboretum (planted in 1984) were rated monthly for aesthetic characteristics from September 1992 through October 1997. Three ratings were taken each year during bloom and combined for one average value. Ratings were made on a 1-5 basis with 1 = outstanding flower, fruit, foliage, form, and other qualities at time of rating. Results are presented as averages, over the five years, in Table 1. Similar results for 14 additional crabapple selections (planted in the 1990s), rated only from November 1996 to October 1997, are presented as averages for that period in Table 2.
From 1995 through 1997, crabapples were scrutinized for season of fruit impact every other week starting at petal fall. Effective fruit is defined as the period from when the tree's fruit first contributes to tree aesthetics until fruit is no longer ornamental.
| Table 1. Aesthetic Evaluations of Crabapples at Secrest Aboretum: 1993-1997 | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| FRUIT | FLOWER | ||||||||
| Crabapple | Fruit Color | Season of Impact1 | Bloom Color1 | Bloom Days2 | Bloom Time2 | Tree Form | Scab3 | Aesthetic Rating3 93-97 Avg. | Comments +: positive aspects -: negative aspects |
| 'Adams' | deep red | mid-July to mid-Oct. | pink | 8 | M | rounded spread | minor | 3.3 | +: abundant tear drop fruit; attractive striated bark on branches and flaking trunk bark; -: 2- and 3-yr.-old mummies; chlorotic summer foliage. |
| M. baccata 'Jackii' | maroon red | late July to mid-Dec. | white | 10.3 | E | rounded upright | none | 2.7 | +: glossy green foliage; wonderful fall yellow foliage accents the maroon fruits; bark has orange cast - : sparse fruit clusters; mediocre winter appeal. |
| 'Beverly' | pink-red | mid-Aug. to late Sept. | white | 14.3 | E | upright spreading | none | 3.5 | +: abundant fruit; consistent floral display is fabulous -: fruits half-eaten by birds; large, persistent fruit mummifies into black blobs until spring. |
| 'Bob White' | yellow | mid-Oct. to late Jan. | white | 14.5 | M | rounded | none | 2.8 | +: abundant yellow-gold fruits mature to orange-gold; standout for winter landscape; outstanding bloom -: alternate bloom; lacking summer appeal. |
| 'Candied Apple' | cherry red | none - scabby fruit | pink | 12.3 | M | unique spreader | major | 3.6 | +: red-tinged new foliage; unusual, irregular weeping form; namesake fruit color -: heavy scab year will mask fruit color and can almost defoliate tree. |
| 'Centurion' | red | late Sept. to mid-Nov. | rose | 11.5 | M | unique open | minor | 3.3 | +: unusual, irregular open branching habit; rust-orange fall foliage effect; nice bloom -: sparse, dull fruit; mediocre in appearance throughout much of the year. |
| 'David' | scarlet | mid-Sept. to mid-Nov. | white | 13.7 | M | rounded | trace | 3.2 | +: snow-white flower display; impressive cherry-like fruits -: alternate bloom; large mummies hang until mid-winter; mediocre appeal until bloom. |
| 'Dolgo' | red-purple | early Aug. to mid-Sept. | white | 13.7 | E | broadly rounded | none | 3.6 | +: consistent early, large, fragrant blooms; edible, large neon red-purple fruit +: rotten fruit is a fermenting mess; big fruit mummies are ugly. |
| 'Donald Wyman' | bright red | mid-Sept. to late Mar.. | white | 15.5 | L | broadly rounded | minor | 2.5 | +: excellent floral display; glossy, exfoliating trunk bark; persistent fruit a mud-red after freeze -: mummies; heavy fruit scab can reduce appeal. |
| M. floribunda | yellow | mid-Oct. to early Nov. | white | 12.3 | M | broadly spreading | trace | 3.0 | +: commingling of yellow and cider brown fruit; wonderful airy floral display -: yellow flecking of foliage; mediocre tree most of the year. |
| M. halliana 'Parkmanii' | yellow | mid-Oct. to early Nov. | white | 11.5 | M | rounded | trace | 2.9 | +: attractive blend of yellow and cider red-brown fruits; light, airy aspect to bloom -: mundane appearance through most of the year. |
| 'Harvest Gold' | yellow | late Oct. to mid-Dec. | white | 11 | L | upright | major | 3.4 | +: yellow-gold fruit clusters accented by red pedicels; alternate bloomer -: long period of green fruit; extensive scab yearly; fireblight is a concern. |
| 'Henningii' | orange-red | mid-Sept. to early Nov. | white | 11.7 | M | upright splayed | major | 4.0 | +: consistent, profuse bloom; attractive fruit in early fall -: extensive leaf scab; ungainly upright growth is a landscape liability. |
| 'Hopa' | red | none - insect damage | pink | 8 | M | broadly splayed | major | 4.3 | +: good pastel floral display -: ungainly tree form; large, gnarly, deformed fruit from coddling moth larvae; wormy fruit drops all summer. |
| 'Indian Magic' | red-orange | mid-June to late Mar.. | pink | 13.7 | M | rounded | major | 2.6 | +: incredible fruit display; consistent, profuse floral display; persistent fruit; fall foliage color -: yearly leaf scab and defoliation by mid-summer. |
| 'Indian Summer' | red | early June to mid-Feb. | rose-red | 14 | E | rounded | major | 2.7 | +: prolific fruit display; consistent large blooms; orange fall foliage; flaky bark on trunk -: yearly extensive leaf scab; persistent mummies. |
| 'Liset' | maroon-red | early July to mid Nov. | rose-red | 14.5 | L | open rounded | trace | 3.1 | +: attractive fruit display; red-maroon new foliage turning bronze green -: awkward splayed form; mummies; minimal fruit to foliage contrast. |
| 'Mary Potter' | red | mid-Aug. to late Nov. | white | 11.5 | L | weeper spreader | trace | 2.3 | +: consistent, petite, abundant fruit; fantastic floral display; elegant appearance; salmon-colored underbark -: mummies distract mid-winter. |
| 'Molten Lava' | red | early Aug. to mid-Nov. | white | 13 | M | broad spreader | minor | 1.8 | +: outstanding fruit/fall foliage combination; excellent horizontal layered branching; consistent bloom -: cluttered, dense, lacks summer appeal. |
| 'Ormiston Roy' | orange | mid-Sept. to late Mar. | white | 13 | M | broadly rounded | trace | 2.8 | +: wonderful glossy, oval-shaped persistent fruit; orangish bark deeply furrowed; good floral display -: mummies may remain up to a year. |
| 'Prairifire' | purple-red | early July to mid-Nov. | coral-red | 13.2 | L | rounded | none | 2.2 | +: firm fruit with white speckles; yearly spectacular bloom; airy structure; peach-orange fall color -: lacks winter and early summer appeal. |
| 'Professor Sprenger' | orange-red | late Sept to mid-Nov. | white | 12.2 | M | upright spreader | trace | 3.3 | +: consistent, large flower display -: dull appearance of large yellow-green fruits during summer; mummies persist until late winter; awkward tree form; severe frogeye leafspot. |
| 'Profusion' | maroon | mid-July to mid-Oct. | purple-red | 10 | M | upright spreader | major | 3.4 | +: abundant fruit; new foliage emerges purple-red -: floral show lacks contrast with foliage; yearly scab problems cause leaf defoliation. |
| 'Radiant' | red | none - scab ravaged | deep pink | 10.7 | M | broad upright | major | 4.1 | +: bloom is pleasant -: yearly scab ruins fruit and causes leaf defoliation; mummies cling on tree well into the next summer. |
| 'Ralph Shay' | red | early Sept. to mid-Nov. | white | 11.7 | M | broadly rounded | major | 3.4 | +: great floral display -: very large fruit can be messy; insect feeding will cause misshapen fruit; mummified fruit is a problem. |
| 'Red Barron' | dark red | none - scab ravaged | red-pink | 10.5 | M | narrow upright | major | 4.2 | +: unique pumpkin-shaped fruits -: sparse floral show; heavy fruit scab and leaf defoliation; fruit blackens with age; ungainly, unsightly form. |
| 'Red Jade' | red | early Sept. to mid-Nov. | white | 13 | M | weeper spreader | minor | 2.1 | +: large, prolific bloom; reliable fruit and flower display; graceful growth habit -: unsightly fruit rot in Jan.; scab on fruit can dull appearance. |
| 'Red Jewel' | cherry red | early Sept. to mid-Apr. | white | 13 | L | narrow upright | none | 2.8 | +: phenomenal fruit; great flower display; can become alternate bloomer -: tree form is somewhat ungainly. |
| 'Red Splendor' | red | late May to mid-Dec. | rose pink | 15.5 | E | upright spreading | major | 2.9 | +: exceptional profuse red fruits; fruit matures to orange-salmon color; reliable fruit and flower display -: heavy scab can defoliate tree; fruit mess. |
| 'Robinson' | dark red | none - lack of contrast | deep pink | 12 | L | round spreader | major | 3.8 | +: attractive flower display -: small fruit; lacks fruit-foliage color contrast; coarse tree form; heavy leaf scab can defoliate. |
| 'Royalty' | red-purple | none - lacks contrast | pink | 11.2 | M | upright open | major | 4.1 | +: purple leaf color -: lacks fruit/flower contrast; ungainly tree form; blackened fruit mummies; leaf defoliation from scab. |
| 'Ruby Luster' | rose-purple | none-unattractive fruit | pink | 11.2 | M | rounded open | major | 4.2 | +: -: large coarse fruits; rough scaly fruit finish; gnarly shape from insect feeding damage; diminutive flowers hidden by newly emerged foliage. |
| M. sargentii | red | mid-Aug. to late Nov. | white | 11.2 | L | wide spreader | none | 2.8 | +: petite firm fruits; attractive low-spreading form; reliable fruit/flower display -: fruits rapidly deteriorate and shrivel like raisins. |
| 'Selkirk' | red | early June to mid-Aug. | rose red | 11.5 | E | wide rounded | major | 3.5 | +: red-tinged new foliage; excellent floral show -: scabby fruit; large fruits drop all summer from insect feeding; lacks winter appeal. |
| 'Sentinel' | red | early Sept. to mid-Feb. | white | 13 | M | narrow upright | minor | 2.6 | +: spectacular pink-tinged bloom; persistent firm small round fruits; reliable fruit/flower display -: persistent mummies detract in spring and summer; upright habit lost somewhat as plant ages. |
| 'Silver Moon' | burgundy | early Sept. to early Dec. | white | 9.2 | L | oval upright | none | 3.2 | +: glossy unique colored fruits; good late floral display -: erratic alternating bloomer; densely cluttered growth; fireblight can be a problem. |
| 'Snowdrift' | salmon-red | late Sept. to mid-Nov. | white | 10.2 | M | broadly rounded | major | 3.0 | +: reliable excellent flower display; distinctly colored small round fruits -: fruit shrivel by late fall; chlorotic summer foliage; extensive leaf scab. |
| 'Strawberry Parfait' | red-cream | early June to late Jan. | pink | 14.7 | E | open spreading | trace | 2.7 | +: reliable fruit/flower displays; abundant persistent fruits; stunning sugar white flowers; good tree form -: fruit drops all at once before bloom. |
| 'Sugar Tyme' | bright red | mid-Sept. to mid-Mar. | white | 13 | M | rounded | trace | 2.4 | +: outstanding floral display; red-tinged newly emerged foliage; unusual growth form; firm persistent fruits -: persistent fruit mummies. |
| 'Velvet Pillar' | reddish | none - lacks contrast | pink | 9.5 | L | oval upright | major | 3.6 | +:purplish foliage; nice tree form -: meager fruit; lack of fruit/foliage contrast; mummies hang on tree in spring; dingy foliage. |
| 'White Angel' | red | mid-Nov. to early Feb. | white | 9.7 | M | broadly rounded | none | 3.4 | -: abundant fruits; reliable fruit/flower display; attractive bloom -: awkward growth until tree matures; mummified fruit hangs until spring. |
| 'White Cascade' | yellow | none - heavy scab | white | 14.2 | M | true weeper | major | 2.8 | +: exquisite flower display on cascading branches; appealing weeping form -: overall dingy summer appearance due to extensive scab; leaf defoliation. |
| 'Winter Gold' | yellow | early Nov. to mid-Dec. | white | 12.2 | M | upright | major | 3.6 | +: butter yellow fruit clusters contrast with bright red pedicels; impressive bloom -: erratic alternate bloom; heavy fruit scab; green fruit for long period. |
| M. zumi 'Calocarpa' | bright red | mid-Sept. to mid-Dec. | white | 12.2 | L | rounded spreader | trace | 2.9 | +: reliable fruit/flower display; abundant tiny red fruits; excellent floral show; nice tree form -: shriveled fruits; lacks winter appeal. |
| 1 Season of fruit impact derived from biweekly observations from 1995-1997 only. Effective fruit impact is defined as the period from when the tree's fruit first contributes to tree aesthetics until the fruit is no longer ornamental. | |||||||||
| 2 Bloom days and bloom time are derived from daily observations from April-May in 1995-1997 only. For bloom time, E (Early) = onset of first bloom in last week of April; M (mid-season) = onset of first bloom in first week of May; and L (Late) = onset of first bloom in second week of May. Bloom days are defined as starting with the emergence of the first flowers and ending when overall flower effect was no longer ornamental. | |||||||||
|
3 Scab and aesthetic ratings are from 1993-1997. None = No scab noted. Trace = A few leaves or fruit affected; no negative effect on aesthetics. Minor = Significant defoliation and/or leaf yellowing; negative effect on aesthetics. Major = Severe defoliation and discoloration of leaves; serious negative effect on aesthetics. | |||||||||
| Aesthetic Rating Scale Ratings include flower, foliage, form, and fruit characteristics, and effects of disease and pest problems. The rating system is as follows: 1 = Exceptionally ornamental crabapple. Based on outstanding flower, foliage, fruit, or form at time of rating. 2 = Highly ornamental crabapple. Good flower, foliage, fruit, or form at time of rating. 3 = Adequate as a landscape crabapple. Not highly ornamental at time of rating. 4 = Substandard as an ornamental crabapple at time of rating. 5 = Ornamentally unacceptable as a landscape crabapple at time of rating. Not recommended for use in the landscape. | |||||||||
| Table 1. Aesthetic Evaluations of Crabapples at Secrest Aboretum: 1993-1997 | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| FRUIT | FLOWER | ||||||||
| Crabapple | Fruit Color | Season of Impact1 | Bloom Color1 | Bloom Days2 | Bloom Time2 | Tree Form | Scab3 | Aesthetic Rating 1997 | Comments +: positive aspects -: negative aspects |
| 'Adirondack' | orange-red | early Oct. to mid-Dec. | white | 12 | L | narrow upright | none | 3.0 | +: narrow upright form; red-tinged flowers; nice autumn fruit/foliage effect; fruit darkens with time to deep orange-gold -: fruit sparse and at top. |
| 'Camelot' | rose-pink | early Aug. to late Oct. | white | 14 | L | low spreader | trace | 3.0 | +: low spreading form; fuschia-tinged flower; oblong fruit; foliage dark green with burgundy overtones -: dull leaf appearance; slow growing. |
| 'Canary' | yellow | early Sept. to late Oct. | white | 12 | M | open spreader | minor | 3.4 | +: clusters of tiny fruit; nice autumnal fruit/foliage effect -: some defoliation caused by scab; fruit deteriorates, turning cider-brown, then falls off. |
| 'Candymint' | red-purple | early July to mid. Dec. | pink | 14 | M | low spreader | none | 2.1 | +: great overall form; reliable fruit/flower display; purple-tinged leaves -: slow growing; dull leaf appearance. |
| 'Glen Mills' | bright red | early Sept. to mid April | white | 10 | M | rounded spreader | minor | 2.7 | +: petite profuse fruit is sensational; long lasting fruit effects -: fast growing large tree; mediocre summer appeal. |
| 'Golden Raindrops' | yellow | mid-Oct. to mid-Dec. | white | 10 | L | open spreader | none | 2.4 | +: interesting cutleaf foliage; petite abundant fruit; reliable fruit/flower display; great autumnal leaf color -: bland green fruit through summer. |
| 'Lancelot' | yellow | early Oct. to mid-Nov.. | white | 12 | L | dense upright | trace | 2.9 | +: diminutive size; consistent tree form -: tight dense branching structure; fruit/flower mostly hidden on the interior of the plant. |
| 'Louisa' | lemon-gold | late Sept. to mid-Dec. | pink | 13 | E | true weeper | none | 2.0 | +: outstanding tree form is its greatest asset; fruit develops a rose blush; -: scattered, sparse fruit. |
| 'Naragansett' | cherry-red | early Sept. to mid-Jan. | white | 15 | M | broadly rounded | major | 3.1 | +: consistent bloom; abundant fruit -: cluttered dense branching structure; fruit scab; tree form awkward. |
| 'Pink Satin' | dark red | none - scab ravaged | pink | 10 | L | upright spreading | minor | 3.7 | +: nice true pink bloom -: abundant persistent blackened mummies are overwhelming; cluttered branch structure. |
| 'Prairie Maid' | orange-red | early July to late Oct. | deep pink | 13 | L | rounded | none | 2.7 | +: reliable wonderful bloom; abundant clusters of fruit -: lacks winter appeal; waxy coating dulls fruit finish until coating is lost. |
| 'Purple Prince' | deep purple | early July to late-Dec. | rose red | 13 | E | broadly round | none | 2.7 | +: large unusually colored fruit; consistent flower/fruit display; fast growing; leaves deep purple green -: somewhat lacking winter appeal. |
| 'Silver Drift' | cherry red | early Sept. to mid-Mar. | white | 13 | E | broadly round | trace | 2.9 | +: nice persistent showy fruit, nice fruit/new leaves contrast -: some fruit mummies; fruit hidden by foliage. |
| 'Sinai Fire' | orange red | early Sept. to early Sept. | white | 14 | M | unique weeper | none | 2.7 | +: unique growth habit; large flowers -: scattered sparse fruit; unique form can limit usage. |
| For an explanation of the aesthetic rating scale, scab rating key, and fruit and flower data, see the footnotes for Table 1. | |||||||||
From 1995 through 1997, crabapples were studied to determine days of effective bloom from mid-April through May. Effective bloom was defined as starting with the emergence of the first flowers and ending when overall flower effect was no longer ornamental. The average onset of first bloom is reported as E ( Early) = last week of April, M (Mid-Season) = first week of May, and L (Late) = second week of May.
Apple scab is reported due to the significance of this disease on aesthetics of crabapples. Incidence of scab is derived from the accumulated disease ratings (three to four per year) on the crabapples in the plot from 1993 to 1997 (1997 only for the 14 additional crabapple selections).
The crabapple plot was planted in 1984 in a completely randomized design with three replications of each crabapple. The cultural practices used to maintain the crabapple plot are minimal pruning, a 6- to 8-foot diameter mulch ring of a 1-2 inch depth around each tree, and removal of rootstock suckers and dead branches, thereby mimicking the cultural practices of an average landscape.
In our opinion, some ornamental crabapples are not attributes in the landscape due to a severe lack of aesthetic qualities. This deficiency of aesthetic appeal may be in part due to extensive defoliation or fruit deformation from apple scab, ungainly tree form, retention of mummified fruit, sparse clusters to no fruit, coarse or dull fruit finish, cluttered branching structure, or a general lack of ornamental effect. Any combination of these aesthetic defects would be extremely difficult to overcome. The trees listed in Table 3 are trees that have consistently demonstrated a substandard performance.
| Table 3. Ornamental crabapples in the Secrest plot with severe scab problems and/or lacking other pleasing, consistent aesthetic qualities. | |
|---|---|
| 'Beverly' | 'Red Barron' |
| 'Dolgo' | 'Robinson' |
| 'Harvest Gold' | 'Royalty' |
| 'Henningii' | 'Ruby Luster' |
| M. adstringens 'Hopa' | 'Selkirk' |
| 'Profusion' | 'Velvet Pillar' |
| 'Radiant' | 'Weeping Candied Apple' |
| 'Ralph Shay' | 'Winter Gold' |
It should be noted that both 'Dolgo' and 'Beverly' are resistant to apple scab. However, their blandness after bloom will not merit their use in most landscapes because both trees have large fruits that mature and drop.
Due to the prolonged cool (compared to averages for the past two years) moist weather this spring, the overall average days of bloom length was increased by two days. The four crabapples that did not show an increase in bloom length were M. floribunda, M. halliana 'Parkmanii,' 'Harvest Gold,' and 'Winter Gold.'
The aesthetic qualities of 44 crabapples (Table 1) were evaluated monthly for more than four years. Monthly ratings were combined, and the average derived for each crabapple selection. This mean is useful in determining the true character profile of a crabapple. Although there are both high and low ratings during a single year, averaging the ratings should eliminate uncharacteristic fluctuations. This cumulative mean is therefore the best indicator of how a crabapple will perform aesthetically in the landscape.
Fourteen new crabapples (Table 2) were evaluated this year, and the aesthetic mean and bloom length for these trees represents only one year of data. Therefore, the profiles of these new crabapples may not be an accurate or complete representation of their aesthetic qualities. More research is needed to confirm these findings and/or correct the inaccuracies.
It must be noted that these crabapple profiles of fruit, flower, form, and disease observations are limited to one site, Secrest Arboretum in Wooster, Ohio. Other limitations of this study, which can affect ratings, are the preferential biases of the evaluators as well as the inability to keep environmental conditions uniform. The lack of control over environmental conditions can directly impact aesthetic aspects like return bloom, bloom duration, fruit development, and ultimately tree size and form if conditions become severe.
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Chatfield, J. A., Draper, E. A., and K. D. Cochran. 1997. Duration of Fruit Effectiveness and Blossom Longevity in Ornamental Crabapples at Secrest Arboretum in Wooster, Ohio: 1995-1996. Ohio Agricultural Research and Development Center. Special Circular 154. Ornamental Plants: Annual Reports and Research Summaries. In partnership with Ohio State University Extension. pp. 41-48.
den Boer, John H. 1995. Blossom Times. Malus. International Crabapple Society Bulletin. 9(1). pp. 10-16.
den Boer, John H. and Thomas L. Green. 1995. Disease and Aesthetic Ratings. Malus. International Ornamental Crabapple Bulletin 9(2). pp. 8-56.
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Draper, Erik A. and James A. Chatfield. 1996. Emergence, Longevity, and Aesthetic Evaluations of Flowers in Ornamental Crabapples at Secrest Arboretum in Wooster, Ohio: 1995. Ohio Agricultural Research and Development Center. Special Circular 152. Ornamental Plants: Annual Reports and Research Summaries. In partnership with Ohio State University Extension. pp. 27-31.
Draper, Erik A. and James A. Chatfield. 1996. Evaluation of Crabapples for Apple Scab at the Secrest Arboretum in Wooster, Ohio: 1994-1995. Ohio Agricultural Research and Development Center. Special Circular 152. Ornamental Plants: Annual Reports and Research Summaries. In partnership with Ohio State University Extension. pp. 22-26.
Draper, E. A., Chatfield, J. A., Cochran, K. D., Bristol, P. W., and C. E. Tubesing. 1996. Evaluation of Crabapples for Apple Scab at the Secrest Arboretum in Wooster, Ohio: 1995. Ohio Agricultural Research and Development Center. Special Circular 152. Ornamental Plants: Annual Reports and Research Summaries. In partnership with Ohio State University Extension. pp. 22-26.
Draper, E. A. , Chatfield, J. A., Cochran, K. D., Bristol, P. W., and C. E. Tubesing. 1997. Evaluation of Crabapples for Diseases at the Secrest Arboretum in Wooster, Ohio: 1996. Ohio Agricultural Research and Development Center. Special Circular 154. Ornamental Plants: Annual Reports and Research Summaries. In partnership with Ohio State University Extension. pp. 35-40.
Green, Thomas L. 1991. Malus for All. American Nurseryman. 173(6). pp. 76-87.
Guthery, David E. and Edward R. Hasselkus. 1992. Jewels of the Landscape. American Nurseryman. 175 (1). pp. 28-41.