|Ribes Species and White Pine Blister Rust – An Update, June 9, 2015
Over the past several years, interest has increased throughout the Northeast in growing and cultivating currants, gooseberries and other species in the genus Ribes for backyard and commercial fruit production. Stimulated by development of varieties that were either resistant or immune to the white pine blister rust pathogen, Cronartium ribicola, several states, including New York and New Hampshire, have eased the once-standard and universal quarantine of Ribes plants that protected the white pine resource and that had been in place for many decades. Unlike other neighboring states, Maine never changed its Ribes quarantine law, and now that decision has come to work to our advantage. A new strain of the pathogen C. ribicola, identified in late 2010, is now known to be able to infect previously resistant and immune species and cultivars of Ribes.
A study was completed in 2014 by the USDA Forest Service to determine the effects of this new strain of C. ribicola on Ribes and the white pine hosts in New Hampshire. The presence of C. ribicola was confirmed on 17 of the 19 immune or resistant Ribes cultivars screened. The study also reported an 18 percent probability of finding white pine blister rust on pines neighboring black currants that were infected with the new pathogen strain but only a 2 percent probability of finding the rust on pines neighboring pathogen-free Ribes. The difference was highly significant both statistically and epidemiologically. The full report appears at http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-12-14-1338-RE.
Results from this study show that the breakdown of resistance in Ribes poses a significant threat to the white pine resource and to cultivated Ribes production. For this reason, all Maine farmers and gardeners need to be aware that the state quarantine prohibiting the culture of European black currants (Ribes nigrum) and all its cultivars throughout the state, and prohibiting European black currants and all other Ribes spp. in the defined quarantine zone, remains in effect. The map and town list of the Maine quarantine areas can be viewed at
William D. Ostrofsky, Forest Pathologist
Maine Forest Service
By Jean English
Many home and commercial apple growers lamented the small crop they had this year, despite hours of tree care. If only we’d planted passionflowers, persimmons or pawpaws! We all realize the benefits of diversity in our society and in our agriculture, but when it comes to fruits, we seem to be stuck growing and eating just a few of the biggies. Lee Reich is out to change that.
At the Common Ground Fair in September, Reich, author of Uncommon Fruits for Every Garden (Timber Press, 2004; $24.95 & $3 shipping and handling from www.leereich.com), spoke enthusiastically about several cold hardy, tasty fruits that have survived in his Zone 4 garden – some surviving -39-degree F. temperatures. He tempted a standing-room-only crowd with descriptions and photos of plants that generally have few or no pest problems, may not need to be pruned, may be ornamental, and may not be available any way other than growing them yourself.
Gumi, Eleagnus multiflora, is a medium to large shrub with pretty fruits that taste a little astringent but have a nice flavor when they ripen in July. The plants don’t need full sun. Nobody has done any breeding with the species, but both the famous plant scientist George Darrow and Lee Reich think that great improvements are just a selection or cross away.
Autumn olive, Eleagnus umbellata, is listed as invasive in the East but tastes good, says Reich. The yellow-fruited variety is less invasive and has a “quite tart” taste, although the tartness decreases in late September. The USDA is looking into this species as a rich source of lycopene. (Note that people who are battling this species for its invasiveness, including my mother, would be upset to see it listed here.)
Maypop, Passiflora incarnata, is an herbaceous vine with perennial roots that is “worth growing just for the flowers,” says Reich. Its egg-sized fruits have a gelatinous covering around the seeds and provide the main taste in Hawaiian punch. To help these plants overwinter, mulch them.
Gooseberry, Ribes hirtellum and R. uva-crispa, and currants, R. rubrum, R. sativum, R. petraeum, are banned in much of northern New England, but this is a “bogus ban” said Reich, because they are not good alternate hosts for the white pine blister rust disease. Reich grows only dessert varieties and eats them raw. ‘Pink Champaign,’ a tart red currant, is easy to espalier.
Alpine strawberry, Fragaria vesca, has an intense flavor when completely red, and doesn’t spread by runners, as the more common strawberry does, so the plant “stays in place.”
Shipova, X Sorboyrus auricularis, which is quite rare, is “like the best tasting pear you ever ate.”
Beach plums, Prunus maritima, tolerate poor conditions, which is why they grow on beaches, but they grow well elsewhere too. They ripen in mid-September, and newer, named varieties (Raintree Nursery has one) taste better than the species. They bloom prolifically every year, but fruiting is variable from year to year.
Reich also noted that lowbush blueberries and lingonberries have tasty fruits, but not many gardeners plant them. The former make a nice ground cover; lingonberries are harder to establish than lowbush blueberries.
Next Reich talked about uncommon fruits that are also “really nice ornamentals.” They include:
Clove currant, Ribes odoratum, with yellow flowers that dangle from branches and a vanilla-like scent that permeates the yard. Again, this is not a good alternate host for white pine blister rust. Fruits have an aromatic, sweet-tart flavor, and the plants take any amount of cold, heat, drought and other adverse conditions. Plants spread by runners that send up sprouts.
Hardy kiwifruit, Actinidia arguta and A. kilomikta, were introduced at the end of the 19th century as ornamentals, and around 1980, people caught on to the fruit. Kolomikta is hardier and smaller and has some variegated leaves, while arguta is not variegated and ripens later than kolomikta. These rampant vines do have to be pruned; and they need well drained soil and full sun or a little shade. You’ll need one male plant to pollinate about eight females. The plants need protection (e.g., a cornstalk mulch) from cold when they’re young; they become hardier with age. Reich likes the variety ‘Ananasnaya’ and says that ‘Esai’ is neither as hardy nor as self-pollinating as it’s billed to be.
Juneberry, Amelanchier species, is not uncommon in the wild but could be planted more as an edible ornamental. It has nice flowers and fall leaf color, and fruits that look like blueberries but have a different taste and, unlike blueberries, do not freeze or cook well. Reich says this is the plant he’s been least successful growing, because it suffers a number of pests; I echo the sentiment. This year I finally cut down my Amelanchiers and will be happy to enjoy them in the wild.
Cornelian Cherry, Cornus mas, is related to dogwoods, and its fruits were eaten from about 7,000 years ago until the end of the 19th century, then their popularity declined, except in the Ukraine. Their fruit tastes like tart cherries. The medium-sized tree requires full sun, has very few pests, and does not need to be pruned.
Nanking Cherry, Prunus tomentosa, represents another opportunity in breeding. Reich grew his from seeds, and every plant is good. The easily grown plants prefer full sun and bear within two years, when a profusion of white, early spring flowers is followed by small, tart, cherry-flavored fruits with pits. Birds and squirrels eat the fruits, said Reich, “but they don’t make a dent.” Sometimes plants will die back or become blighted. In that case, Reich advises cutting the growth back and sticking another plant in.
Next, Reich discussed fruits that have been selected for superior quality and have named varieties.
American persimmon, Diospyros virginiana, is known for the extreme astringency of its unripe fruits, but when ripe, the fruits taste “like an … apricot dipped in honey with a little spice added.” Reich advised growing varieties that are hardy and will ripen in your area. ‘Szukis’ is one of his favorites; it does not need a pollinator, and the fruits hang on the tree until December. Reich advised removing some of the precocious fruits when the tree is young so that the plant becomes established better. ‘Mohler’ is another good variety. Reich does not like the ‘Meader’ variety, because it retains a little astringency even when ripe, but noted that some people like that.
Medlars, Mespilus germanica, were a favorite plant of Charlemagne: Each town that he conquered had to plant a medlar tree. Reich said the trees are pretty but the fruits are ugly. They bloom late, so you don’t have to worry about frost killing the flowers. Fruits are picked just as the leaves are about to fall, are put in a cool room, and are ready to eat in about two weeks, when they’re brown and mushy and look disgusting inside. “It’s one of the best fruits I grow,” said Reich, comparing the flavor to applesauce and apple butter, but richer. He does not note much difference among varieties.
Pawpaws, Asimina triloba, have fruits that hang in bunches like bananas and foliage that resembles that of an avocado tree. The small tree has “interesting flowers” and creamy fruits that taste like bananas and custard with mangos and other tropical flavors mixed in. They have virtually no pests; need full sun; and need two varieties for pollination. While named varieties exist, Reich said that plants grown from seed are also good.
Sources of Plants
Reich listed eight nursery sources; I’ve added Fedco Trees, since it’s a Maine-based co-op. (Disclaimer: I grow some ornamentals for Fedco.)
Burnt Ridge Nursery, 432 Burnt Ridge Rd., Onalaska WA 98570; 360-985-2873; www.burntridgenursery.com/
Edible Landscaping Nursery, Rt. 2, Box 77, Afton VA 22920; 800-524-4156; www.eat-it.com
Fedco Trees, PO Box 520, Waterville ME 04903-0520; 207-873-7333; www.fedcoseeds.com
Hidden Springs Nursery, 170 Hidden Springs Lane, Cookeville TN 38501; 931-268-2592; www.hiddenspringsnursery.com/
Oikos Tree Crops, PO Box 19425, Kalamazoo MI 49019-0425; 616-624-6233; http://oikostreecrops.com/
One Green World, 28696 S. Cramer Rd., Molalla OR 97038; 877-353-4028; www.onegreenworld.com
Raintree Nursery, 391 Butts Rd., Morton WA 98356; 360-496-6400; www.RaintreeNursery.com
Saint Lawrence Nurseries, 325 State Highway 345, Potsdam NY 13676; 315-265-6739; www.sln.potsdam.ny.us
Whitman Farms Nursery, 1420 Beaumont NW, Salem OR 97304; 503-585-8728; www.whitmanfarms.com