Ornamental Plants

Annual Reports and Research Summaries

Special Circular 152-96

Emergence, Longevity, and Aesthetic Evaluations of Flowers in Ornamental Crabapples at Secrest Arboretum in Wooster, Ohio: 1995

Erik A. Draper
James A. Chatfield
Kenneth C. Cochran

Erik A. Draper, Ohio State University Extension-Mahoning County; James A. Chatfield, Ohio State University Extension-Northeast District/Horticulture and Crop Science; and Kenneth C. Cochran, Ohio Agricultural Research and Development Center/Secrest Arboretum/ Ohio State University Agricultural Technical Institute

Abstract

Forty-six ornamental crabapple (Malus spp.) selections were evaluated for timing and duration of bloom. These selections were also appraised three times during the bloom period for aesthetic qualities of blossoms in addition to other factors that either enhanced or detracted from bloom. This study defined the reference bloom base of 'Dolgo' (the first crabapple to bloom) as zero, 0-3 days later as very early, early as 4-6 days, mid-season as 7-9 days, and late as 10+ days after reference bloom. Twenty-nine of the 46 selected crabapples retained their blooms at least 10 days or longer in 1995. 'Strawberry Parfait' had the most durable blossoms, lasting for 16 days, while 'Velvet Pillar' was the shortest at only five days.

Introduction

Flowering crabapples (Malus spp.), as indicated by their common name, are most often planted in landscapes for their magnificent bud colors and floral displays during spring. If the sole emphasis is floral display then those crabapples whose flowers and buds are showy for an extended period of time should be of greatest value. Unfortunately, crabapple bloom is presently classified in loosely defined group designations of "early, mid-season, or late bloom" rather than periods of time. Also, if relative times of blossom emergence and longevity are known, then it is possible to create an extended continuous display of flowers by combining crabapples that flower at different times.

Den Boer (1) offered a method, Blossom Time Index, to describe the sequence of bloom. The sequence of bloom was categorized for all crabapples in reference to Manchurian crab, the earliest bloomer. All subsequent crabapple bloom emergence was based on number of days after the reference bloom. However, den Boer did not indicate longevity of bloom. Longevity of bloom is directly affected by environmental factors like wind, rain, high, and low temperatures. A combination of bloom emergence with relative time of effective blossom duration would be an extremely useful tool for assisting in landscape design decisions.

This study was initiated to determine relative times of blossom emergence and longevity that directly affect aesthetic qualities of ornamental crabapples.

Materials and Methods

Forty-six selections of crabapples at the Ohio Agricultural Research and Development Center's Secrest Arboretum in Wooster, Ohio, were evaluated daily, 24 total times, from April 26, 1995, through May 20, 1995. Recorded observations for each crabapple included days of first blossom fully open, and the period when crabapples were past effective bloom display (50 percent or greater loss of overall blossoms).

Relative bloom times will be reported as indicated by den Boer (1) as days after bloom emergence for the earliest blooming crabapple, or reference base. The reference base for the Secrest plot was the crabapple 'Dolgo.'

Three aesthetic assessments were also conducted on April 29, May 6, and May 13, 1995. Subtleties such as early bud color, bud/leaf color complement, bud/flower contrasts, clear blossom colors or tints or lack of these aesthetic qualities were important aspects of these ratings. Other factors such as tree shape, mummifed fruit, and other components affecting aesthetics also influenced ratings. The assessment ratings were based on the following criteria:

1 = Exceptional ornamental crabapple. Based on outstanding foliage, flower, fruit, or form at time of rating.

2 = Highly ornamental crabapple. Good foliage, flower, 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.

These crabapple selections were planted in 1984, in a completely randomized block design with three replications of each selection. The cultural practices used to maintain the crabapple plot are minimal pruning, 6-8 foot diameter mulch ring of a 1-2 inch depth around each tree, and removal of rootstock suckers and dead branches, mimicking those cultural practices of an average landscape.

Results and Discussion

The reference base crabapple, 'Dolgo,' first began blooming on April 26, 1995, and 17 days later, on May 13, 1995, 'Silver Moon' was the last to begin flowering in the plot. 'Strawberry Parfait' had the most durable flowers at 16 days and was spectacular in overall bloom aesthetics. Conversely, 'Velvet Pillar' flowered very late, offering blossoms for the shortest duration of five days and rated the poorest aesthetically.

For this study we defined the blossom times of very early as 0-3 days from reference bloomer ('Dolgo'), early as 4-6 days, mid-season as 7-9 days, and late as 10+ days. Three crabapples were very early bloomers, 11 were early bloomers, 19 were mid-season, and 13 were late bloomers (see Table 1).

Very early blooming crabapples averaged a blossom longevity time of 14 days, early bloomers duration averaged 12.5 days, mid-season bloomers duration averaged 10.5 days, and late bloomers blossom longevity averaged 8.5 days. Twenty-nine of the 46 selected crabapples retained their blooms at least 10 days or longer. A relatively mild winter and ideal spring weather possibly provided optimal conditions for maximizing bloom and longevity of blossoms.

The aesthetic ratings indicate many crabapples provide a highly ornamental floral display. Thirty-five of 46 crabapples received an average rating of 2.5 or better. Although many of the crabapples were highly ornamental at this point in time, it is but a brief moment relative to the length of the crabapple season. Therefore, to be most effective as a landscape component, other aesthetic characteristics, such as fruit display or disease profiles, must be known and scrutinized (2,3,4,5).

The top 12 aesthetically rated crabapples during bloom were 'David,' M. halliana 'Parkmanii,' 'White Cascade,' 'Bob White,' 'Mary Potter,' 'Sugar Tyme,' M. zumi 'Calocarpa,' 'Donald Wyman,' M. floribunda, 'Molten Lava,' 'Sentinel,' and 'Strawberry Parfait.'

Selecting crabapples with high aesthetic ratings and combining blossom emergence with bloom longevity makes it possible to create a flowering impact in the landscape for as long as three weeks. Ideally, choosing crabapples that flower about one week apart would result in the longest floral display.

However, the use of ornamental crabapples solely as flowering trees without recognizing other aesthetic characteristics, positive or negative, which crabapples create, can seriously detract from or greatly enhance the landscape.

It must be noted that these observations are limited to one site, Secrest Arboretum in Wooster, Ohio, and are for one year only. Other limitations of this study include preferential biases that may influence evaluators, the inability to maintain equivalent weather conditions throughout the blossom period, and lack of environmental modifications to reduce tree stress cycles that can affect bloom.