Glazed vs Unglazed pots question

Jo Ann

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Hi
I was looking at Darrell's post and I wanted to say very beautiful pots. My question is for root health is a glazed pot better or unglazed? Right now everything I have is growing in terra cotta clay pots. 1 its cheap and 2 it seems to let the roots breath better and 3 I have nothing close to being ready to put in a nice bonsai pot anyway. Any comments?

Jo Ann
 

Rick Moquin

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The simplest answer is no. High fired pots do not breath perse compared to low fired terra cota. The importance is that the inside be unglazed so the roots have something to cling to.

When it comes down to aesthetics, now that's a whole different kettle of fish.
 

rlist

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Compared with terra cotta, there is reduced air transfer through the pot wall with high fired pots, and then even further reduced with a glaze. This is ok with maples that like a little extra moisture, but is not ideal for pines that like to dry out. Now, how much are we really talking about offsetting the health of the tree when we use free draining soil, have ample drainage holes and a large surface area? Dunno, but aeration of the soil should always be in your thoughts when potting. A world famous pot builder once told me that terra cotta is excellent for grow pots because of the aeration, they just need to be replaced rather often.
 

Rick Moquin

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Rich,

I was of the same opinion up until last year, when a lengthy discussion ensued at IBC. High fired, high/good quality pots do not breathe whether glazed or not. The reason I omitted a discussion of the delta between the two (glazed and unglazed) was wrt the breathability of the containers vice aesthetics. Perhaps a potter can jump in on this one and explain in layman's terms what takes place at different firing levels.

On my own front, I do have several trees under develoment in terra cota bulb pots, where one can clearly see the leaching through the parent material. With the exception of the calcium build up at soil level on both my glazed/unglazed pots, no leaching is apparent. One advantage terra cota does have over high fired pots, is the material can be wetted down during high summer heat IOT provide cooling for the roots.
 

Boondock

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A trees only interest in a bonsai pot, is the negative space that a bonsai pot creates. It's the place in the pot, where there is no pot. Like the water that is displaced in the exact negative space of a boat's hull.
 
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BonsaiWes

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I have answered this "newbie question" probably 100 times so far in my life. The tree doesn't really care if the pot is inner glazed or not, as far as keeping the root system stable use wire because it is more reliable. A good bonsai soil will provide enough air to the roots on it's own! The REAL reason pots aren't commonly glazed on the inside is that it is a waste of supplies and effort since the inside is never displayed.


It is funny, so many porcelain pots are used world wide and have been for many many many years, I have never seen one that wasn't all slicked up inside. A pot doesn't have to "breathe", just needs to drain..well, unless it's a bald cypress pot.. .
 

Tachigi

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Hi
Right now everything I have is growing in terra cotta clay pots
Jo Ann, Most the people above have addressed this issue fairly well. The only thing I might add is that your terracotta pots will have a tendency to steal water. As we all know this type of pot wicks water rapidly from any surface that it is intimate with. So keep this in mind with your watering regiment.
 

Graydon

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It is funny, so many porcelain pots are used world wide and have been for many many many years, I have never seen one that wasn't all slicked up inside. A pot doesn't have to "breathe", just needs to drain..well, unless it's a bald cypress pot.. .
Well put. Pots breathing when you have all of that exposed soil surface area for water to evaporate? Nah...

Even a bald cypress likes drainage. They are some of the most drought tolerant natives here in Florida... just my observance as to how they grow in nature. Really wet and in standing water during our rainy periods and then dry as a bone the rest of the year.


Jo Ann, Most the people above have addressed this issue fairly well. The only thing I might add is that your terracotta pots will have a tendency to steal water. As we all know this type of pot wicks water rapidly from any surface that it is intimate with. So keep this in mind with your watering regiment.
I have started to wax the inside of my terra-cotta pots when I get them. Beeswax and spar varnish mix I use in woodworking. Wipe on - wipe off. No more water wicking. Keeps the outsides pretty free of that nasty slime they develop down here as well simply by sealing the inside.
 

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