rainwater is normally neutral which means it has a pH of 7

It is good, but since it is entirely pure, it will have no mineral contents. If your plants only get rainwater you'll have to add fertilizer.

Really you shouldn't worry if it's rainwater or tapwater. They're about the same. Just make sure it isn't overwatered or underwatered.


This is what any plant in nature needs:

1. Water (doesn't matter what water as long as it isn't poisined)
2. minerals (fertilizers are almost pure minerals)
3. carbon-dioxide (atmosphere usually has enough)
4. light (sunlight is the best, but good artificial lighting will do)