TrapsAndDews wrote:How much water do Nepenthes need?
Maybe about two cups a week. Nepenthes don't like to keep their feet wet, so you water them thoroughly and then let them dry out a bit between waterings. Typically two or three times a week. If you can grow some live sphagnum on top, it'll help show you when it dries out.
TrapsAndDews wrote:Also, what kind soil and pot size should they have?
Typically good sphagnum moss makes up the base. No peat moss. From there it depends on the type of nepenthes and how frequently you are prone to watering. If you water frequently (3 times a week) you'll want to add in a healthy dose of perlite and orchid bark. If you water less frequently (1 or 1.5 times a week) a heavier does of sphagnum to perlite is helpful. Small nepenthes typically grow in a 4" pot. Medium in a 6-8" pot. Large in a 10" pot. Give or take. There are some photos of nepenthes growing in 55 gallon trash cans, but those are the exceptions. Because nepenthes like to dry out between waterings, I use net pots. But that depends on your conditions (not required).
TrapsAndDews wrote:How fast do they grow?
It really depends on the nepenthes and it's conditions. Some are super slow to grow. I've had a hamata for 6 months and it probably put out two leaves in that time frame. Most put out probably 1 leaf per month or so. Some of the more vigorous growers (sanguinea for me) will put out a leaf every 10 days or so. If you get a small nepenthes it will typically stay in the smaller stage for 2-5 years. Then it'll start typically vining. It doesn't need to (you can trim it at that point).
But if the nepenthes really likes its conditions it can take off. I put a nepenthes in a fishbowl terrarium at work and it grew from about 3 or 4 inches to filling out the bowl in 10 months. I took it out and replaced it with another nepenthes, and the same thing happened.
Generally speaking, nepenthes doesn't like to be repotted frequently. It is notorious for pitching a fit when it's roots are disturbed. Meaning it freezes in place and refuses to grow for a period of time. Less picky plants will pout for a month. More picky plants will pout for up to a year. So leave it's roots alone. Pot it up, and let it do it's thing. If the plant is sucking up water frequently, then it's telling you it needs a bigger pot. Otherwise (unless the medium started to break down) leave it be.