It's more difficult to grow plants (especially those that don't tolerate wet feet with grace) in shallow pots than in deep pots; this, because at container capacity (when the soil has stopped draining and is holding as much water as it can) deep pots will have a higher % of unsaturated grow medium than shallow pots.
The images below are filled to the top with a grow medium that supports excess (perched) water.
If the pots are 12", 8", and 12" deep. It's easy to see that the shallow pot has less than 25% of well aerated medium at container capacity, while the 8 & 12" pots have about 62% and 75% (respectively) of well aerated media at container capacity.
What the plant would prefer is, being grown in a deep pot with plenty of room for roots to run ..... not a shallow pot that quickly constricts roots and leaves only a small % of unsaturated medium after a thorough watering. It's better to eliminate both horns of a dilemma than to choose the lesser of two evils.
Al
