Elbow Room and Food
What’s happening in the soil beneath your potted plants? Over time, roots fill up the pot so there’s little more room left for them to grow. And nutrients get sucked out of the soil or washed out by water.
I keep my potted plants hale and hardy with periodic repotting. This also gives me a look at the roots, which I always find interesting. (It was one area of my research when I worked for Cornell University.) If I see roots are pressed around the outside of the rootball, especially if traveling around and around it, they’re telling me they want out. A plant might also indicate its roots need more elbow room by looking like it’s ready to topple over. More subtle signs are potting soil that dries out very quickly, a plant hardly growing, or roots attempting escape out a pot’s drainage holes.
Rapidly growing plants need repotting yearly, especially when they are young; older plants and slow growers can get by with being repotting every two or three years. Some plants hardly ever need repotting, such as — looking around my collection — my amaryllis (Hippeastrum), bay laurel, hardy cyclamen, jade plant, aloe, and cactus.
I wait to repot my ponytail palm until its bulbous base breaks open the pot it’s growing in; this happens about every 15 years. Same goes for my clivia.