Crabapples are now, more than ever, a popular and attractive choice for ornamental landscapes, both public and private. Crabapple trees are hardy, adaptable to various soils, and come in a wide range of sizes and shapes. Varieties are available to suit almost any purpose, from small urban gardens, entry courtyards, and parking strips to public parks and highway plantings. Crabapples bloom profusely in eye-catching shades of pink, red, and white, sometimes accented by purple or bronze leaf color. Their coloration makes them effective ornamental trees in the spring landscape.
Many older crabapple varieties grown in the past adapted poorly to the cool, moist climate of the maritime Pacific Northwest. Too often, diseases such as scab and powdery mildew took their toll. Following the attractive blooms of April and May, severe infections turned the trees into leaf-shedding eyesores by the end of the summer and threatened their long-term survival. It usually required an aggressive spray program to keep disease-susceptible trees healthy and attractive. Intensive spraying, costly in terms of both labor and materials, is particularly impractical for large areas such as parks and roadsides. Aside from the expense, spraying of pesticides is increasingly seen as undesirable in urban and residential locations.
Because several varieties formerly sold and planted, such as 'Hopa,' 'Van Eseltine,' and 'Eleyi,' are quite disease susceptible, crabapples have lost favor in areas where fungal diseases are common, and have been eliminated from many landscape plantings. Better crabapple varieties now are available that carry proven disease resistance. These resistant varieties have attractive bloom equal or superior to the older varieties. They also will keep their healthy leaf canopy intact through the summer and into fall. Some turn color in late autumn. Many produce full crops of small bright fruit that decorate the branches well into the winter and provide food for overwintering birds. They are worthy of a prominent place in any landscape.
In 1984, Dr. Tom Green of the International Ornamental Crabapple Society worked with Washington State University to establish a test planting of crabapple varieties at WSU Mount Vernon. Dr. Green furnished trees and organized the trials for disease resistance nationwide. It was one of 23 original test sites located throughout the country to test resistance under varied climate conditions. Many introductions tested in the program have improved resistance to serious diseases such as scab.
Researchers rate all varieties annually in spring and fall. Most crabapples are attractive in bloom, so although the spring rating is an important element of any variety's overall performance, the most critical evaluation is how the trees look in the fall. The spring evaluation emphasizes bloom time (early, mid, or late), appearance (flower and leaf color), and fragrance. The fall rating covers tree habit, appearance and disease symptoms. To receive a high rating, a variety should retain most or all of its leaves in a healthy condition throughout the summer and must have abundant, vividly colored fruit that does not drop and make a mess (Figs. 1, 2). The preference is for small fruit of 1/2" diameter or less, but larger sized fruit is acceptable if it remains firmly attached to the tree until it dries up (e.g., 'Evereste,' see cover) or is eaten by birds.
Although a variety having proven immunity to disease infection is usually the best choice, a tree's good appearance is not always totally related to its level of disease resistance. Certain crabapple varieties, although somewhat susceptible to scab or other diseases, still keep their leaves and continue to look attractive in late summer and fall. In some varieties the leaves may drop fairly early in the fall, but trees remain attractive with colorful fruit that hangs on well into the winter (Fig. 3). Performance ratings of the different crabapple varieties discussed in this bulletin are based on data and observations taken of the WSU Mount Vernon plot from 1984 to 1994. Since apple scab is the most serious disease to which crabapples are exposed in a cool, damp climate, researchers have kept a scab rating on all varieties in the trial (see tables below.)
This guide primarily reports on varieties that are well adapted for ornamental and landscape purposes. In most cases the fruit is too small, bitter, or sour for human consumption, although birds and other wildlife often are attracted to it as a winter food source. Some crabapples have fruit suitable either for fresh eating or for culinary purposes. These larger-fruited varieties are generally not good choices for ornamental use, because excess fruit tends to drop and rot, making an unsightly mess on lawns and walkways.
|DUAL-PURPOSE (ORNAMENTAL AND CULINARY)|
Among the crabapple varieties that merit consideration for eating fresh or for culinary uses, 'Dolgo' is probably the most commonly planted. Serious drawbacks are its high scab susceptibility, which requires an aggressive spray program for good control, and the early-ripening fruit that drops rapidly if not harvested. The apples are quite tart, mainly good for jelly or pickled fruit. 'Evereste' and 'Ralph Shay' produce heavy loads of round, very tart fruit that hang on the trees through the winter. 'Evereste' has excellent scab resistance, needing no spray, while 'Ralph Shay' is moderately susceptible and will need a basic spray program to remain attractive.
'Whitney' is an older variety, having large, mildly subacid fruit that can be eaten fresh from the tree. 'Centennial,' developed in Minnesota, produces attractive red and yellow fruit with a pleasant sweet-tart flavor. 'Chestnut,' originating in England, has red striped, partly russeted fruit that is sweet and crunchy with a distinctive nutlike flavor. 'Whitney,' 'Chestnut,' and 'Centennial' all would require a basic scab spray program to ensure good harvest of usable fruit. All the varieties mentioned above have white bloom. In our trials pink-flowered crabapples with edible fruit, such as 'Red Flesh' and 'Almata,' have proven too scab susceptible for general use, as the trees would need an aggressive spray program to maintain good health.
Listed in the tables below are ornamental crabapple varieties that have done well at the test site near Mount Vernon in the Skagit Valley. We anticipate that their performance will be similar in other cool maritime areas of the Pacific Northwest. For easy comparison, we have divided the varieties into sections according to bloom color and tree shape. Upright trees (Fig. 4) are tall and narrow; upright spreading trees (Fig. 5) are tall but have branches that open out as the tree matures; and rounded trees (Fig. 6) have a compact, densely branched, nonspreading habit. Broad spreading trees, whether large or small, have a flattish, horizontal limb structure (Fig. 7). As they mature, some broad spreading trees develop limbs that tend to grow downward, and are termed semiweeping (Fig. 8). Trees with a fully weeping habit are those in which most or all branches trail downward even when trees are quite young (Fig. 9).
Within each section, varieties appear in alphabetical order, giving information on bloom time, fruiting, tree vigor, and scab rating. A few brief comments cover any additional details. Bloom time for crabapples varies somewhat with the season and location, but observations at the test site since 1986 indicate that on average the early bloom begins in early April and the late bloom continues into early or mid-May. We refer to fruit set as "abundant" when most or all branches of the tree are filled with fruit, "moderately abundant" when most branches have some fruit, and "sparse" when fruit is scattered on occasional branches or grows in small quantity.
In evaluating vigor we can only estimate exact dimensions since the plot is only 11 years old. The relative size of same-age trees gives good indication of their size at maturity. "Highly vigorous" trees have the largest current tree volume (15' or above in height or breadth 11 years after planting). "Low nonvigorous" trees have the least volume (5' to 8' in height, with corresponding breadth). Trees having "moderate vigor" fall midway between vigorous and nonvigorous (10' to 15' approximately). When fully mature, the most vigorous crabapples can reach 30' in height and have corresponding width, while the smallest (e.g., M. sargentii) may be no more than 8' tall.
We rated the trees for scab each year in September or October, using a scale where 5 equals no visible scab lesions on leaf or fruit, all leaves remain on tree; 4 equals scab detectable but most leaves are not infected, most leaves remain; 3 equals scab easily found on most leaves but causes little defoliation; 2 equals scab abundant on nearly all leaves, and up to 50% defoliation; and 1 equals bare tree. Crabapple trees rated at 4.5 or above have very good scab resistance. Those rated 3.5 to 4.5 are moderately resistant and generally acceptable for planting. Trees rated 2.5 to 3.5 are moderately susceptible and should not usually be planted; while those rated below 2.5 are very susceptible and should be avoided in most cases. Our goal is eventually to develop a good selection of scab-immune crabapples suitable to different landscape purposes, and gradually to discontinue use of susceptible varieties.
|TOP RATED VARIETIES|
|Of the nearly 60 different crabapples that WSU has evaluated in this trial since 1984, perhaps a dozen stand out as top performers. All have attractive, profuse bloom in spring. Many are fragrant. Their level of disease resistance, particularly to scab and mildew infection, is good to excellent. While not all of these varieties are suited to every landscape application, taken together they provide a wide selection of proven high quality. Listed in alphabetical order, they are|
|A number of established crabapples that are not quite up to the standards of the top rankusually because of higher scab susceptibilityare very acceptable for ornamental landscape uses and may be easier to find in nurseries. New introductions with higher disease resistance or other special qualities will eventually overtake varieties such as 'Mary Potter,' 'Ralph Shay,' 'Snowdrift,' and 'Donald Wyman.' However, these offer a significant improvement over the disease-prone, poorly adapted varieties of former years.|
|VARIETIES TO AVOID|
|Although some of the following disease-susceptible varieties still may be sold locally on the basis of their performance in other parts of the country, they are not well adapted to the cool maritime climate areas of the Pacific Northwest. As a result of our testing program and studies, we do not recommend planting these crabapples.|
Better crabapple varieties are available that are disease resistant and easily maintained, and that add to the year-round aesthetic value of the landscape. We encourage parks departments, homeowners, and landscape designers to try these new, recommended crabapple varieties and to become familiar with their versatile qualities as ornamental plants. Ask for them at nurseries. Nursery professionals can gear their production toward increased use of the high-rated varieties.
Promising new crabapples, not yet fully evaluated in western Washington, include 'Prairie Maid,' an attractive pink (Fig. 16); 'Adirondack,' a late white bloomer with upright habit; and 'Morning Sun,' a white bloomer with abundant yellow fruit that lasts well into the winter. Two compact varieties with very dwarf tree habit that may do well in patio or container gardens are pink-flowered 'Lancelot' and white-flowered 'Camelot.'
Development of new disease resistant varieties continues, leading to crabapples that will need little or no spray for disease control. Unique leaf shapes, bloom colors, attractive winter berries, variable tree sizes and habits are all possibilities for future improvement. We plan to continue testing these high quality crabapples to provide a wide selection for gardeners, homeowners, and landscapers. At the conclusion of the project we hope to have a full range of crabapple choices well adapted to our maritime climate conditions. The versatile crabapple now merits a prominent place in the western Washington landscape.
|Dr. Tom Green of the International Ornamental Crabapple Society initiated the trials. The Washington State Nursery Association contributed financial support for the project. Their help and support are gratefully acknowledged.|
By Gary A. Moulton, M.S., Washington State University Scientific Assistant, WSU Mount Vernon Research and Extension Unit; Jacqueline King, M.A.,WSU Technical Farm Laborer, WSU Mount Vernon; and Raymond Maleike, Ph.D., WSU Cooperative Extension Horticulturist, WSU Puyallup. All photos by Jacqueline King.
College of Agriculture and Home Economics
Washington State University Cooperative Extension bulletins contain material written and produced for public distribution. You may reprint written material, provided you do not use it to endorse a commercial product. Please reference by title and credit Washington State University Cooperative Extension. To reproduce photographs used in this bulletin, please contact Jacqueline King.
Issued by Washington State University Cooperative Extension and the U.S. Department of Agriculture in furtherance of the Acts of May 8 and June 30, 1914. Cooperative Extension programs and policies are consistent with federal and state laws and regulations on nondiscrimination regarding race, color, gender, national origin, religion, age, disability, and sexual orientation. Evidence of noncompliance may be reported through your local Cooperative Extension office. Trade names have been used to simplify information; no endorsement is intended. Published February 1996. Subject code 544, 231. K