If there’s one tried-and-true annual for Texas, especially when our stifling summer heat goes to full throttle, has to be the vinca or periwinkle. Unfortunately, standard vincas planted at the wrong time or in wet soil can simply crater within a week. Although they’re supposed to love the heat, what they don’t usually like is overly damp soil. That’s why planting too early has commonly led to root rot. And unusually extreme rains in June and July can lead to a type of root rot known as phytophthora.
Horticultural researchers at Clemson University in South Carolina spent years developing the Cora® brand vinca that had some disease resistance. Then a couple of years ago, the agriculture company Syngenta, well known for developing fungicides, worked with Clemson to take Cora vincas a step further. And now we have the Cora XDR® – which stands for Extra Disease Resistance. Introduced in 2019, they are seemingly impervious to phytophthora.
I often mention Cora XDR and Cora Cascade® vincas on the radio show, so I thought it was worth some detail on these striking and showy plants. They are sort of no-brainers when it comes to summer color these days. The trailing version, by the way, is great for containers and hanging baskets.
A little history while we are it … phytophthora foliage blight is the most damaging and devastating disease affecting annual vinca plants, and it can be super frustrating when it takes out a mass planting of these beauties. But now, we fortunately have these phytophthora-resistant annual vincas that can be grown in landscapes throughout the Southeastern U.S.
The new Cora XDR series has been put through the wringer at Clemson - scientists there have done extensive internal testing, disease screening and multiple field evaluations. Still, that doesn’t mean you won’t lose a Cora vinca now and then … keep in mind that the testing was all done in South Carolina, not in any Texas Gulf Coast gardens.