A Cook's Garden: Overcoming a few bad apples
It is a tale of two trees, one happy, one sad. Both of the crab apples in my garden are laden with white flowers in spring, bear red berries that last into the winter, for the birds' pleasure, and sport yellow leaves in fall. But one of the trees sports them all too soon, in summer, when the scab fungus catches up with them. Its berries are sparse. The other tree is a vigorous grower with nary a sign of disease. The two are growing in identical plots, with well-amended soil.
Over in the orchard, where the eating apples are, scab is also in evidence. There, the focus is on the fruits. (Sure, you can make jelly from crab apple fruits, but the tiny size of most of those grown for ornament make them fussy to pick.) The Winesaps in particular have exhibited the telltale signs: little round greenish spots that have darkened into the eponymous scabs, as if they were just recovering from chicken pox. The Golden and Roxbury Russets, on the other hand, are largely unblemished, by scab or anything else.
Scab is a very common disease among apple trees. It's a fungus that attacks in spring, does its work, then overwinters in the leaves and fruits that are shed in fall, until spring rains disperse the spores again. For clear, detailed information about apple scab, consult "The Apple Grower," by Michael Phillips (Chelsea Green, $40).
In most commercial orchards, chemical sprays are used to halt the problem early on. Organic growers substitute sulfur sprays and sometimes dormant oil. But these are cumbersome for home gardeners, who are better off breaking the disease cycle by raking up and burning or composting the dead leaves in fall. Any effort to promote the well-being of a tree may make a difference, too: spacing it adequately at planting time for good air circulation; spreading compost beneath it (and lime as needed) to add fertility and encourage earthworm activity; avoiding grass turf and using a straw mulch instead.
Despite your best efforts, certain apple varieties will still be more prone to scab than others. My Winesaps obviously are, and my "good" crab apple, which I suspect to be a Zumi Calocarpa, is not. There are many published lists of scab-resistant apples that you can consult before buying. But bear in mind that different apples get scab in different parts of the country. Scab also mutates, and even ones that are generally resistant may not always remain so. Nonetheless, a lot of fine research has gone into breeding scab-resistant trees. At present, for example, a good eating apple called Liberty will give you excellent odds.
Or, you can decide not to worry too much about it. Our Winesaps this year, despite their spots, made many gallons of the best cider you ever drank, with some of the dark red fruits pretty enough to display in a bowl. And the underdog crab in the garden will remain in there as long as it still erupts in a cloud of white blossoms each spring.
Damrosch, author of "The Garden Primer," is a freelance writer.