You got to the right place - let's wait for what Jon_D has to say.

I forgot I had it, as the plant superficially is similar to hirtellus; and I was growing them outdoors, where they were growing kind of raggedly, covered with oak leaves and generally ignored. Then, a few years ago, I brought them all inside and realized I had two pots of hirtellus and one of 'Petropolis'. I was happy to see I still had this cv., which I had forgotten all about. So, I began propagating it. Last week I was discussing this one with Ingrid in Sweden who is now distributing it there, and she offered that it most likely is a cross of hirtellus and fluminensis, which I agreed. It has an upright habit with large yellow flowers with black maroon calyxes. Compared to hirtellus, the yellow corolla is much larger and showier. Its habit and foliage are close to hirtellus. It flowers over a long period, nearly all year in the greenhouse. Right now it is flowering very nicely.

To grow a nice plant, keep it pinched to force branching. Cuttings root easily, and the plant, like other nematanthus is cold tolerant down to about 30-32 degrees. Like other nematanthus it is an epiphyte, requiring the typical gesneriad mix. For best flowering give it bright shade.

Like hirtellus it has the interesting habit of budding up along the stem, often below the oldest leaves. Often a mature cutting will initiate buds after rooting and being potted up, making a striking small flowering starter plant. Last summer I took a bunch of rooted starts without flowers to the Norcal Cactus and Succulent show/sale. I put them out with a cut stem with flowers for an example. They all sold within the first two hours, and then someone talked me into selling them the cutting (which went back to France!). It isn't succulent but struck a cord.

Jon