The RHS suggests most houseplants need a new pot or fresh mix every two to three years, though a plant that fills its pot sooner will show you the signs from the last lesson.
Timing matters because repotting always disturbs some roots. The best moment is when the plant is starting its active growth, so new roots can quickly settle into the fresh mix. In temperate homes that means spring. In the tropics, where many plants grow year-round, pick a time when the plant is visibly putting out new leaves, rather than when it is resting or flowering.
Good reasons to repot: the plant is root-bound, the mix has broken down and compacted, the mix stays wet and smells sour, or roots are rotting. A green film of algae on the surface can also be a sign the mix is tired. When roots have rotted, repot straight away, whatever the season, and trim away the dark, mushy roots.
Remember that the new pot should be only a little larger, as in lesson 2.
Bad reasons to repot: the plant has just arrived home, or it is already stressed by a move. Let it settle first, as you will see in the next unit.
Key points
- Repot every two to three years, when the plant is actively growing.
- Rotting roots are an exception: repot promptly.
- Do not repot a plant that has only just come home.
Try this
Write down when each plant was last repotted in your plant notes. Mark any that are over two years old to check at their next growth flush.
Check yourself
Read more in the reference
Sources
Marking a lesson done is kept on this device only.