The most common repotting mistake is choosing a pot that is too big for your plant. Moving from a small container to a large one traps excess moisture around roots. This wet soil creates the perfect conditions for root rot to develop and kill your plant within weeks.
I made this biggest repotting error myself with my first fiddle leaf fig years ago. It looked too cramped in its nursery pot so I moved it to a container three sizes larger. The roots sat in wet soil for weeks and the plant died within two months of that well-meaning move.
The pot size mistake causes problems because of how water moves through soil around your roots. A small root system cannot drink water fast enough from a large volume of soil. The soil stays wet longer than it should. Bacteria and fungi that cause rot thrive in these soggy conditions.
Penn State calls oversized pots a top repotting failure causes for your plants. RHS guidance suggests moving up by only one-third in pot size at most. A plant in a 6-inch pot should go into an 8-inch pot at the largest for best results.
The simple rule to follow is 1 to 2 inches larger in diameter than your current container. Measure across the top of your existing pot to find its size. Then shop for a pot that adds just an inch or two to that number for your plant.
Proper pot sizing gives roots room to grow without drowning them in excess moisture. Your soil dries out between waterings at a healthy pace. Roots can access oxygen they need to stay strong and absorb nutrients from the fresh potting mix you provide.
Signs that you chose too large a pot show up within the first few weeks after repotting. Yellow leaves near the base of your plant signal waterlogged roots. Soil that stays wet for more than a week means you have too much volume for your root system to handle.
Fix an oversized pot by moving your plant back to a smaller container right away if you catch it early. Remove any rotted roots you find during the move. Use fresh dry soil and hold off on watering for a few days to let things settle down.
In my experience, the urge to give plants more room comes from a good place but hurts more than it helps. Think of repotting as giving your plant a slightly roomier outfit, not a tent. Your plants will thank you with healthy growth when you size up slow and steady.
Read the full article: How to Repot Plants: 10 Essential Steps
