Pot Depth—Don’t Cut it Close!
The guideline runs: pot depth should equal trunk diameter. This, though, is an aesthetic guideline. Many bonsai prefer a deeper pot.
A deep pot is like sneakers. Good for romping around in. The high heels and dress shoes are for primp, kept in the closet with the shallow show pots for special days.
There are species preferences in pot depth, shared in the following photos-
This Japanese White Pine bunjin is mounded. This adds additional depth to a pot already twice as deep as the thickest trunk. Pines are happiest in deeper pots. (Photo courtesy Bonsai Empire.)
Shore Pine with a trunk girth half the depth of the pot—a good year-round growing pot.
The guideline works better with maples. The pot is as deep as the thickest trunk—a great show pot, and with care can function as a year-round pot. Slightly upsizing this pot would allow greater ease of care and plant vigor.
A Japanese Maple ‘Beni-kawa’ in a shallow pot. (This is an oval pot, photographed from the side.) Maples grow well in shallow pots year-round.
Shrubs are another matter. They do better in deeper pots. I don’t recommend growing Chojubai or Azaleas in shallow pots. Most of my Chojubai are in much deeper pots than this one. This one only works horticulturally as a year-round pot because the soil is mounded.
Another Chojubai. Deeper pots offer easier year-round shrub care.
Skinny-trunked azalea in a deep pot. (Photo courtesy Andrew Robson.)
Carmen, my current apprentice, demonstrating proper wand technique. (Actually what I want you to notice is this Azalea’s largest trunk is about half the diameter of the pot depth. A good year-round growing pot.)
John Eads, past apprentice, with Carmen, both clearly excited by this azalea trunk’s girth being half the depth of the pot (even though flowers are hiding it).
Once you reach this girth, the pot depth can be similar to trunk girth and all is well in shrub land. Deep pots offer better drainage to a greater percentage of the soil mass.
A favorite photo of my teacher, Mr. Shinji Suzuki. This photo is from ages ago. Maybe 2004. He’s sitting next to a Cotoneaster in a pot twice as deep as the trunk girth. A good pot to grow in year-round.