text: I have a few of these 'Star Jasmine' planted to grow on a wall that has vertical wire running the height of the wall approx 12" apart. It's been 6 mos and I'm just not getting the coverage that I want.
  Do these plants require an actual trellis to cover a block wall?
  Star Jasmine (Trachelospermum jasminoides) is a twining vine, though it doesn't twine as tightly as some such vines. It can climb a vertical wire, though horizontal supports would help brace it more securely. Before you invest in a trellis, try manually training the vine up the wire and then anchoring it with tacks or clips if needed.
  They are not the fastest vines to get going. They tend to sit for awhile before really starting to climb. Were they planted as 1 gallon or 5 gallon containers? They don't wrap tightly enough to hold them selves up on skinny, smooth wire very well. Another thing you could try, if you haven't already, is to feed them. I prefer to use water-soluble fertilizers once week to really push plants along.