James A. Chatfield, Erik A. Draper, Kenneth D. Cochran, Peter W. Bristol, and David E. Allen
Twenty-eight crabapples (Malus spp.) plant-ed in 1984 were rated from 1992-1998 for aesthetic qualities, flower duration, season of fruit effectiveness, tree form, and disease characteristics. Fourteen crabapple selections, which were planted in 1994, were also evaluated for those same parameters for only two years (1997-1998). Overall profiles of these crabapples developed from these ratings are presented in this report. Fifteen crabapples were removed from the evaluation plots due to their consistent lack of pleasing ornamental aesthetics.
Crabapples are generally 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-owners, landscape architects, and homeowners alike in their selection of a particular crabapple for a specific landscape use. Understanding the strengths and the weaknesses of each crabapple increases the likelihood of complementing the landscape, rather than causing a detraction.
Twenty-eight crabapples at The Ohio State University/Ohio Agricultural Research and Development Center's Secrest Arboretum were rated monthly for aesthetic characteristics from September 1992 through October 1998. 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 six years, in Table 1.
Similar results for an additional fourteen crabapple selections, which were planted in 1994, and the monthly observations from November 1996 to October 1998 are also presented as averages in Table 1. These selections are noted with an "*" before the crabapple name.
From 1995 through 1998, 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.
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 crabapples in the plot from 1993 to 1998, except for those indicated with "*", which only have two years of data (1997-1998). Detailed results of disease findings are presented in another article of this publication (see page 50).
The original crabapple plot was planted in 1984 with an additional 14 selections planted in 1994. The plot is in a completely randomized block design with three replications of each crabapple. The cultural practices used to maintain the crabapple plot are minimal pruning, a six- to eight-foot-diameter mulch ring of a one- to two-inch depth around each tree, and removal of rootstock suckers and dead branches, thereby mimicking those cultural practices of an average landscape.
In the authors' opinion, there are some ornamental crabapples that should not be used in the landscape due to an overall lack of aesthetic qualities. This deficiency of aesthetics 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 appeal. Any combination of these aesthetic defects would be extremely difficult to overcome. The trees (listed in Table 3) have been removed from our evaluation plots.
The aesthetic qualities of 42 crabapples (Table 1) were evaluated monthly. Those preceded by a "*" only have two years of observations, from November 1996 to October 1998. All other crabapples have been rated for five years. Monthly ratings are combined and an 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.
When aesthetic quality is combined with disease resistance, then customer satisfaction and success will increase. However, this does not mean that any tree that fails to exhibit complete resistance to scab should be avoided in the landscape. There are trees that have a trace of scab that are absolutely superb and would be great additions to any landscape.
An observation worth noting was the impact that the "El Niño phenomenon" had on crabapple bloom. In 1996 and 1997, 'Dolgo' was the first crabapple to bloom -- on the 27th of April. This year 'Dolgo' bloomed a full three weeks ahead of the past two years -- on the 6th of April -- with all other trees following that general trend.
Also of interest was the conspicuous lack of foliage on some crabapples that bore copious amounts of fruit in 1997 and retained that fruit well into the winter months. During the growing season, it was observed that some branches, with last year's fruit mummies still present, had died. Some of these branches did begin to leaf out, but the foliage was small, stunted, and never expanded to a normal size. With the mild winter experienced in the area, this condition was definitely not due to freeze damage. One possible explanation is that the large fruit load exhausted the carbohydrate supply, creating additional stresses on trees, resulting in branch dieback.
The authors believe enough observations have been conducted on the original 28 trees to confidently state that the crabapple profiles created are reasonably accurate representations of how that crabapple will perform. The other 14 crabapples, designated by a "*", were evaluated for just two years, so the aesthetic mean and bloom length for these trees should be considered approximations. Therefore, the profiles of these "newer" 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 that 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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Table 2. Ornamental Crabapples Removed From the Evaluation Plot Due to Severe Scab Problems and/or Lack of Other Pleasing, Consistent Aesthetic Qualities. | |
|---|---|
| 'Adams' | 'Red Barron' |
| 'Centurion' | 'Robinson' |
| M. halliana 'Parkmanii' | 'Royalty' |
| 'Henningii' | 'Ruby Luster' |
| M. adstringens 'Hopa' | 'Selkirk' |
| 'Profusion' | 'Velvet Pillar' |
| 'Radiant' | 'Weeping Candied Apple' |
| 'Ralph Shay' | |
1. 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. Ornamental Plants: Annual Reports and Research Summaries. Special Circular 154. Ohio Agricultural Research and Development Center. The Ohio State University. pp. 41-48.
2. Draper, E. A., Chatfield, J. A., Cochran, K.D., Bristol, P. W., and D. E. Allen. 1998. Comprehensive Aesthetic Evaluations of Crabapples at Secrest Arboretum in Wooster, Ohio: 1993-1997. Ornamental Plants: Annual Reports and Research Summaries. Special Circular 157. Ohio Agricultural Research and Development Center. The Ohio State University. pp. 83-94.
3. Chatfield, J. A. and E. A. Draper. 1995. Evaluation of Crabapples for Apple Scab at the Secrest Arboretum in Wooster, Ohio: 1993-1994. Ornamental Plants: A Summary of Research, 1993-1994. Special Circular 142. Ohio Agricultural Research and Development Center. The Ohio State University. pp.10-12.
4. 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. Ornamental Plants: Annual Reports and Research Summaries. Special Circular 152. Ohio Agricultural Research and Development Center. The Ohio State University. pp.22-26.
5. 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. Ornamental Plants: Annual Reports and Research Summaries. Special Circular 154. Ohio Agricultural Research and Development Center. The Ohio State University. pp.35-40.