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  • Writer's pictureDebbie Woodbury

Rose Collection at Foundation Plant Services

Foundation Plant Services at the University of California, Davis, hosts the largest public collection of virus-tested roses in the United States, and possibly the world. The collection covers 12 acres and includes 957 rose scion and understock cultivars, totaling well over 4,700 plants. From 2015-2021 the collection was held on an 8.5-acre block known as Brooks South. In 2021, several rows of rootstocks ‘RW’ and ‘Dr Huey’ were added to meet industry demand, and the capacity of Brooks South was reached. As a result, a new foundation block was established at Russell Ranch in 2022. The Russell Ranch block is 3.5 acres in size, with capacity for approximately 2,000 rose bushes. Prior to planting at Russell Ranch, roses must test negative for six viruses: apple mosaic virus (ApMV), Prunus necrotic ringspot virus (PNRSV), rose yellow vein virus (RYVV), rose rosette virus (RRV), blackberry chlorotic ringspot virus (BCRV), and rose spring dwarf associate virus (RSDaV).

Rose Rosette virus (RRV) is of particular concern, and since its detection in a commercial nursery in California in August 2017 FPS has strengthened procedures for isolation and testing of domestic and international rose introductions to reduce the risk of RRV transmission to the foundation collection. RRV is associated with rose rosette disease (RRD), which results in symptoms of witches’ broom, mosaic, red pigmentation, excessive lateral shoot growth and thorniness, and eventual plant decline and death.

Along with precautions taken when handling introduction material that could contain RRV, FPS has limited the ability to visit the foundation rose collection. The NCPN-Roses Tier 2 meeting was held at FPS in July 2023. Out-of-town visitors who were willing to wake up early (before it was too hot!), and don a protective suit were able to visit the collection. You don’t have to take such measures to tour the collection – the team also assembled a great video to introduce the program. You can watch the video on YouTube:


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