I would be curious if vinca is affected by any diesese'. I've had it for about 5 years, and it seems like it very hard to kill. I do on occasion get a few dead vines, but not enough to notice with out looking for it. Sorry this isn't much help.

I wish I had some insight, but I'm actually having a very similar problem. We planted about 10 vinca minor plants last year in the early fall, and all of them survived the winter.

In the spring, they all had new growth and looked great after I pruned out the dead stuff. Now the new growth has slowed down, or maybe stopped completely, and lots of the old growth is drying out and turning crispy :( Some of it is turning yellowish and brittle, some brown and brittle.

We just upped the water about a week ago so the soil always feels moist now, but they still don't look any better.

I called the nursery where we got them, and the guy said to put some root stimulator on them and maybe some miracle grow too. We already put root stimulator on them when we planted them ~8 months ago, but I guess I'll try putting on a bit more, though I'm not all that hopeful.

We have ours planted on either side of a walkway between the house and garage, so they only get about 2 hours of sun a day, which shouldn't be too much, even in Colorado. I would love to hear if anyone else has had this problem and found anything that works. I walk on the walkway so often and it's such a downer seeing it look like crap :(

There are two problems that affect vinca, especially in cool, wet weather . . . that is phomopsis blight and rhizoctonia root rot. Thinning out your beds and improving air circulation may help, as well as trying to avoid overhead sprinkling, especially late in the day. For better explanations than I can fit here, google each of these.

Kathie