I was just wondering

I had read that you do not put your plant in too big of a pot, and I wanted to know if it was true and if so why. I was told that it hurts the roots that they begin to rot! That didn't make sense to me because if that were the case wouldn't plants growing outdoors die. I just wanted to get this straight. Maybe I read wrong.

That is true. What happens is if you have a teensy plant in a huge pot, the plant's roots can't take up the vast quantity of available water quickly enough, so it ends up sitting in wet soil constantly. Some plants are OK with having wet feet, but most aren't. If you are careful you won't necessarily kill your plant by doing this, but it greatly increases the chances that you'll overwater the plant (and overwatering isn't that hard to do even in an appropriate sized pot, so why do something that makes it even more likely!)

The reason things are different outdoors is that water moves differently through the soil outdoors than it it does in a container, the whole drainage process works differently. In outdoor soils, the water can continue to drain down through the soil away from the roots. In containers, you will get some water that drains out the bottom of the pot, but you end up with a higher amount of water that's trapped in the pot and if the roots can't take it up quickly, then the soil stays too wet for too long.

I used to question the rule about potting up one pot size at a time. I thought as you did bonez...they grow in much bigger areas outside. As I tend to do, I followed my instincts and potted my plants in containers that I felt I wanted them in when full grown (to save time). They never did very well and after trying everything else, I began going up one pot size at a time. It made all the difference in the world, so I guess I don't know everything- (surprise!). My other mistake was to assume that if a little fertilizer is good, ALOT is better. Wrong!!!

Something else about a pot too large for the size of the rootball ... the plant will concentrate all it's effort on trying to fill up all that space with roots instead producing new foliage and blooms. The most important thing though is as ecrane3 said ... too large a pot and the roots will stay too wet, probably ending up with root rot and the demise of the plant.

We've all been there ... learn by experience. Believe me when I say I have gone through a lot of trial and error experiences in my 40 years of growing house plants!

Thanks everyone its nice to have people to ask who know what they are talking about other than looking through my plant books night and day. I always followed the "pot rule" but my boyfriend and I were talking about it and he wondered as well. oh growgirl my grandpa always used too much fertilizer and I would always tell him thats a little too much but of course to him it was fine lol.

A woman I work with told me her husband said to pot the plants in the largest pot possible, to give them more room to grow.
After explaining why this was wrong, I asked her if she bought her kids clothes this way...after all, the five year old will grow into a sixteen year old's clothes eventually! I think I helped her win her arguement with DH this way. ;)