I have received many questions about rhododendrons that could be considered “tolerant” to Phytophthora from people who have lost plants during the long, warm wet summer. Digging into the archives, I found this article that was published in 1975 by the American Rhododendron Society by research done at The Ohio State University. Though this article was published over 40 years about, many of the hybrids and the species rhododendrons that were available at the time are still available today. I do not carry any on the very short list of resistant hybrids, however I do offer many that are on the second short list of “moderately resistant” and “more tolerant”. These are the plants that we currently offer that are on this list:
English Roseum( Purple, Hardy to -10, 7 Feet) http://oregonrhododendron.com/product/english-roseumaka-roseum-pink/
Mrs. C B Van Nes (Dark Pink, Hardy to 0, 5 Feet) Only limited number available in one gallons – please e-mail.
Rocket (Dark Pink, Hardy to 0, 5 feet) http://oregonrhododendron.com/product/rocket/
Roseum Elegans ( Pink, Hardy -10, 7 Feet) http://oregonrhododendron.com/product/roseum-elegans/
The Honourable Jean Marie de Montague (Red, Hardy to -10, 5 Feet) http://oregonrhododendron.com/product/the-honourable-jean-marie-de-montague/
Vulcan (Red, Hardy to -10, 5 Feet) http://oregonrhododendron.com/product/vulcan/
Vulcan’s Flame (Red, Hardy to -10, 5 Feet) http://oregonrhododendron.com/product/vulcans-flame/
I do not carry any of the species plants that are tolerant or moderately tolerant. Due to the age of this article, there may have been new hybrids that have been introduced or further research done to determine tolerance. Any new information I receive, I will post to this blog. Thank you! Jim
http://scholar.lib.vt.edu/ejournals/JARS/v29n1/v29n1-hoitink.htm