Monday, November 3, 2014
The BEST Crabapples for Minnesota: Height, Fruit, Scab Resistance and Finally: Flowers - Part I
This summer I was asked so many times "What is wrong with my crabapple?" that I started LOOKING anew at crabapples. 2014 was a banner year for apple scab, discoloring the foliage and causing premature leaf and even fruit drop. Affected plants looked dormant, or as many homeowners feared, dead. Apple scab can weaken trees, but rarely is fatal. Scab may allow secondary organisms to attack the tree and can decrease its winter hardiness, so it is best to purchase a scab-resistant crabapple. WHICH crabapples are resistant to scab, is complicated as the newest study (Beckerman et al, 2010) shows a new strain of this disease may now infect previously resistant cultivars. Additionally, we tend to think only about the FLOWERS on crabapples, and especially LOVE the showy pink or red flowers that are unfortunately often more susceptible to scab.
I recommend the first criteria for selecting a crabapple should be the ultimate SIZE, height and shape of the plant, followed by scab resistance, fruit, and finally the flowers. It is a misconception that crabapple fruit is messy: the small colorful fruit (5/8 inch or less) is a valuable food source sought by birds throughout the winter, and adds color and interest for many months.
Late fall is an ideal time to walk the crabapple collection at the Minnesota Landscape Arboretum and pick your favorite, because you can easily select scab resistant plants with clean, healthy leaves. Additionally, you can evaluate the fruit which varies widely in color and can last for MONTHS, easily six or even eight months. Remember that crabapple flowers last only for DAYS, perhaps a week. Why not select a crabapple for healthy leaves, and attractive fruit and just let the flowers be an added bonus?
From endless lists of hundreds of crabapples, the short list below was developed based on fall appearance with clean foliage at the Arboretum. Additionally, these plants are also top recommendations from long-term research trials conducted at the Ohio State University (their Crablandia field plots); Morton Arboretum, Illinois; Purdue University, Indiana; and the multi-state National Crabapple Trials.
I propose these 13 crabapples as "the best" for Minnesota. If your favorite is not here, let me know! All of the plants listed show good to excellent resistance to apple scab with an asterisk * for those showing some susceptibility to the new apple scab strain now in the Midwest. 'Red Splendor' is a showy red-pink prolific flowering crabapple that originated in Minnesota, however, it is susceptible to scab, needs plenty of space due to its large size and can be defoliated and defruited in mid-summer due to scab.
Which one would I plant in my yard? Anyone from this list, but something in the name 'Professor Sprenger' does resonate with me! It is a lovely tree that greets visitors on the Snyder Terrace at the Arboretum. Others you can see easily at the Arboretum are: 'Donald Wyman' planted in mass in the first parking lot bay across from the Oswald Visitor Center; 'Adirondack' marks the entrance to the espalier in the Cloister Herb Garden; 'PrairiFire' makes the double allée at the Sensory Garden, 'Pink Spires' flanks the entry to the new Green Play Yard at the Andrus Learning Center, and two 'Prairie Maid' trees fill an island in the staff parking lot.
There is an amazing variation that exists in these tough plants. A crabapple that grows well in Ohio, may not show the same disease resistance to apple scab here in Minnesota. The weather and climate makes a difference. Touring the famous crabapple collection at the Arboretum and the newer plantings in the display gardens can give you a first-hand look at how the plants grow in our climate. Ideally, we would annually rate crabapples three times: for foliage and fruit in September and October; for winter interest and fruit (bird food) in January; and flowering in May. Look for yourself at a garden center or the Arboretum, so you can decide which form and fruit is best for your garden and landscape.