Mordecai Cubitt Cooke had multiple names and multiple spouses.
According to some sources, this late 19th-century mycologist maintained what many would consider a scandalous family life. Cooke wedded an unmarried woman who already had a daughter named Anne, whom he helped raise. He went on to have children with this stepdaughter, the first child when she was just 17 years old. Anne left Cooke and had children with Cooke’s step second cousin, then returned and had three more children with Cooke. Through this all, Cooke’s first wife and mother of his stepdaughter (and grandmother of her husband’s children with her daughter) remained with him the children until her death.
Even with his chosen profession, I wouldn’t call him fun guy, as his couplings were of questionable integrity. But even with two simultaneous spouses and many children, Cooke still had time and energy to dedicate his life to the study of fungi.
Cooke’s confusing and entwined relationships mirrors that of a fungus that he has been credited with studying and naming. Gymnosporangium clavipes, known as cedar quince rust, also has a complicated lifestyle that includes dual partners and back-and-forth relations.
Cedar quince rust cannot thrive with just one companion — it takes two to tango. The hosts for this fungus include plants in the Juniperus genus, including our local eastern red cedar, and plants in the Rosacea genus, such as apple, crabapple, hawthorn, shadbush, pear, quince and chokeberry.
The fungus moves between both hosts. A wet and warm spring will encourage the growth of its bright orange, gelatinous spores on Juniper trees, its primary host. Its gooey-looking spore horns appear to ooze out of the twigs, branches and trunks of these trees. Called teliospores or telia, the gelatinous globs germinate to produce basidiospore which are carried by wind to their secondary hosts, infecting plants in the Rosaceae family.
Still following? There are only a few more steps to go.
The secondary host species responds with swelling cankers on its twigs and thorns, rust spots or blemishes on its fruit, marks or legions on its leaves, and orange dots on its flowers. Aeciospores or pinkish tendrils on its shoots, leaves and fruits can also result. These appear as alien, stick-like growths, and they are the mechanism that will send back spores to the Juniperus species to infect them. The cycle then continues after the fungus overwinter in the affected trees.
The quince rust fungus can damage all species named above by weakening them, reducing their fruit yields and, certainly, diminishing the aesthetic value of these varieties. This rust is a relative to the cedar apple rust that produces golf-ball-sized gelatinous-fingered blobs in red cedar trees, and while similar, the conditions they produce are like comparing apples to quinces.
Experts do provide suggestions for reducing the occurrence of this multi-phased and multi-faceted fungus. Proximity is a problem, so make sure that the above-named Juniperus and Rosacea species are not planted too close to each other. If they are, move one further afield. When selecting plants, choose resistant varieties and manage moisture so they are not too wet. If you do notice a problem, prune and remove infected plant parts and dispose of them away from infectable and vulnerable plants.
Even with all of our efforts, the wild relationship between fungus and fruit will continue to grow, as quince rust can be found in both natural and landscaped environments. Look for the telltale carrot-colored jelly on cedars this time of year, and the peculiarly-affected fruits come summer. Perhaps like the untraditional Mr. Cooke, you may accept any damage that ensues as simply a by-product of a complicated, chaotic relationship.
Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown, and author of Martha’s Vineyard: A Field Guide to Island Nature and The Nature of Martha’s Vineyard.
This article appears in May 22, 2026.