I have talked to hundreds of customers troubleshooting the issues their leafy babies are having at home. We go through all the basic questions - What light is it getting? How often are you watering? When was the last time it was fertilized? One question usually gives them pause - How large is your plant in comparison to your pot?
Over-potting is a common problem with new houseplant enthusiasts. Simply put: the larger your pot, the more soil it contains; the more soil there is in a pot, the longer it takes to dry out. It is incredibly important to choose your pot based on the size of your root system. If your plant has la lot of foliage but its root system is only a few inches long - it is not ready to be moved into a larger pot. If your root system is disproportionately small in comparison to its pot the roots can be overwhelmed with saturated soil - and prone to root rot.
When roots are oversaturated - they can die from a lack of oxygen. As these dead roots decay - this decay can spread to your other roots and cause additional die-off. This means that even if you see signs of overwatering - and amend your watering schedule accordingly - the damage can continue to progress. If your plant is showing symptoms of over-watering (yellowing leaves, stunted growth, brown or mushy stems), always check your roots for more information.
I highly recommend choosing a pot that offers no more than 2 inches of additional room between your root ball and the sides of your pot. This gives your plant ample space to grow without dramatically increasing the time it takes for your soil to dry.
Photo 1: A six inch pot is too large for these spider plant cuttings. There is far more than 2 inches of additional room around the root system. Up-potting this much can leave your plant at risk for root rot.
Photo 2: This 2.5 inch pot is just right for these spider babies. The roots have approximately 2 inches to grow into but won't be overwhelmed with a huge amount of soil.