Pothos, Epipremnum aureum, is an epiphyte so an orchid mix for epiphytes would be perfect.

Don't use vigoro, it's just Home Depots' cheaper version of potting soil, probably made somewhere in China. Get a decient potting soil like Myke or Pro-Mix. Miracle-Gro is pretty bad too.

Rhizo, if you'd had any significant experience in growing Pothos, Epipremnum aureum, you'd realise your comments are off the mark.

I've never grown them in an orchid mix, or seen them grown in such, but that doesn't mean it won't work. They can easily be grown in either the gritty mix or the 5:1:1 mix.

It's easy to overlook the fact that plants in containers may very well not prefer the same type of root medium in which they grow in situ. As long as you provide a medium that holds little or no perched water, you water/fertilize appropriately, and give the plant the light/temperature it prefers, you'll be fine.

The key to providing a healthy root medium lies not so much in what materials the soil is made of; rather, in the size and uniformity of the particles that make up the medium. The potential for your plant to prosper is much greater in a soil that has a favorable structure and no organic fraction than it is in a soil with a significant organic fraction but with an unfavorable structure.

Al

From what I've read, Epipremnum has (at least) three modes of growth: up a tree, down from a tree, and along the ground toward a tree. The main thing that turns on each program is the direction of gravity, but I would guess that rooting conditions would matter too. In particular, I would expect it to be quite willing to use its climbing roots to gather rainwater on the side of a tree, given the demands of lifting water from the ground. After all, it's very willing to root from a node when you stick a cutting in a glass of water.

My actual experience is very limited. I have one with small solid-green lanceolate leaves and medium-sized variegated heart-shaped leaves on the same plant, which I think is neat. I want to try to get its climbing roots going in true climbing mode, eventually.

i rooted a bunch of stems in long fibre sphagnum and they are still in it a year later doing great! and on water-wicks (self-watering) too. growing largest leaves ever.

Are they growing up, down, or horizontally?

Epipremnum aureum will grow in almost any potting media you can get as long as it is kept moist and doesn't compact and promote rot. Orchid bark should work fine as long as it doesn't dry. They also do great growing in just water as well.

they are hemiepiphytes, They start where-ever the seed drops whether that's a tree branch or the ground. They grow up and downwards sinking roots in the soil and reaching up to the sun. By nature they are not epiphytes.

i hooked some of mine to grow up on the support - not all, but some cuttings produced very thick stem and doubled the size of leaves. i want to curl it on a circle and root it flat in a saucer, while still attached to original plant. then cut it off , clip the curled stem and wait for sprouts. i hope since the bottom leaves would be large, the new leaves would also be larger then regular stems.
i will also train them vertically. may be this way i can produce a large-leaf 'totem' eventually.