Terra Cotta Pots modified for Bonsai purposes

River's Edge

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When developing Bonsai we are often looking for more economical containers for growing out developing stock. Terra Cotta can be an option for some climates with a few modifications. I have experimented with them for five or six years now and find them useful and economical.

I am working with two sizes of the Azalea style terra cotta that is basically wider and shorter than most clay pots. Often sold as bulb pots. the two sizes I have selected are 10 inch or # 27 in reference to the diameter of the rim. And the 8 inch diameter.
The modifications I make are to add drainage holes and slots for the excess water to escape from under the pot when placed on a flat surface.

Simple tools that you can obtain easily or borrow from a friend that likes to build.
Drill that can take a carbide multipurpose bit and adjust the speed.
Angle grinder with masonry cut off wheel.
Safety equipment to prevent injury, goggles, face shield etc.

Specifics that I use. Mad Dog multipurpose bits, Norton masonry cut off blade,

Benefits.
terra cotta retains moisture and cools roots on hot days.
relatively inexpensive for repeated use 10 inch size under $10 8 inch size under $5
additional holes provide tie in for Bonsai and adequate drainage.
slots allow air under the pot for exchange and moisture transfer.
Terra Cotta has weight advantage over plastic if tipping is a concern and the wider Azalea style is more stable than the normal shape!
Disadvantages
Not for use in heavy frost areas.
Takes a bit of effort to modify!

Extra Tips
Speed most effective around 600 to 800 rpm with carbide bits.
Set the bottom of the pot in water for a few minutes before drilling or cutting, prevents chipping and dust from drilling. Debris rinses off easily.

Pictures below to illustrate.
 

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Firstflush

Shohin
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I have larger terracottas that aren’t in use. Instead of buying shallow grow out pots, I was thinking of cutting some height. Have you cut a rim off any to shorten them? Maybe a dremel with a masonry cutting wheel....

Also, maybe you are or aren’t aware, nice shallow “bulb“ terracottas are available out there for sale.

One disadvantage is that they will dry your soil quicker due to the porosity of the material which wicks water from the soil. If you need wet conditions, watch your water :)
 

River's Edge

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Also, maybe you are or aren’t aware, nice shallow “bulb“ terracottas are available out there for sale
I thought I indicated I was using the shallower Azalea/ bulb style. Not the shallowest as they are very poor for developing Bonsai, I prefer at least a 3-4 inch depth as a minimum for developing or maintaining bonsai.
One disadvantage is that they will dry your soil quicker due to the porosity of the material which wicks water from the soil. If you need wet conditions, watch your water :)
I would not consider this a disadvantage, as one needs to adapt watering to suit mixes and containers in all bonsai applications. Perhaps that falls into the suitability for ones climate, although the cooling effect of transpiration and lighter color could be advantageous in warmer climates as well.
 

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