I feel so strongly about trying to dispel this myth, I copied/pasted that from my profile on here. I put it there for whoever clicks on "me" to consider. One has to grow according to their soil, so if it's peaty potting soil and taking forever to dry out, a tiny pot, rootbound condition, &/or drying to the point of almost-wilt may be tools for survival, at best, but not conditions by which to grow an optimal specimen.
Roots that have filled a pot, &/or formed a pancake shape at the bottom of a pot are also very exposed to periods of being too dry, then too moist, hot/cold, and completely vulnerable when in a weakened state to pests like root mealybug. When roots are no longer able to grow, the foliage is not either.
For those having trouble overwatering, this is a really tough tightrope to walk, you can't make mistakes. It's so much easier to just be able to be wrong, and give plants a drink before that magic moment when they're about to wilt but haven't yet. You still can't take the very 'best' mix and keep a cactus moist, but you sure can avoid overwatering other plants that like and need to stay moist by just continuing to love & water them like always, in a soil that's not conducive to rotting the roots while moist.
An argument could also be made that because 'new' plants usually need to mature before blooming, maturing would likely often coincide with filling its' pot with roots.
To have a great plant, it must have great, healthy, growing roots.
Understanding the roots of the myth (pun intended) can help with understanding how to get past it. No doubt it may have been a workable tool in the past when bagged peat began to be marketed as a potting medium, or may even come from a prior time when ground dirt was the only option. To compound things in recent times, some potting soil has silicone gel bits that exacerbate the moisture retention problem because the predominance of tiny particles of peat requires some drying for roots to get oxygen before that is even added. It would be more accurately called moisture retention soil, not moisture control. By understanding more about how roots work and what happens to them in a pot in different types of soil, we are more able to provide more suitable, less risky conditions. Something I'm constantly working on, and I look forward to learning more!
