I think it is just the weight of them. Many of the people here that grow citrus in pots live in colder climates where the pot has to be moved inside during the winter. If there is a reason not to, I'd sure like to know as I plan on doing it.

If you look at using a ceramic pot and or plastic from a plants perspective, then they would much more prefer clay since they are gas-permeable.

Using ceramic and or plastic usually arises out of grower convenience. Many like them because they are either pretty, readily available, or sometimes even lighter than clay.

I suppose many don't care how a plant feels, since they don't have feelings, so it's a matter of choice. I myself am guilty of using plastic and ceramic on a few of mine.

Mike:-)

Ashley,

In addition to the reasons given by others, I would add that ceramic pots have a few other potential drawbacks. First, they are fragile in comparison to plastic pots--one sharp blow inflicted while moving a ceramic pot around on your patio will likely reduce it to shards. Second, they are more expensive. Third, their shapes can be ill-suited to transplanting needs (I've noticed that many ceramic planters intended for annuals have bellies that will never yield up a rootball).Fourth, writing as someone who has a degree and 30 credit hours of graduate coursework in ceramics, I'll add that many of the ceramic pots may be toxic in some small way over time either to the plants or the people who might consume their fruit. This is particularly true of those ceramic pots with colorful glazes, but if people wish to use glazed pottery for growing edible plants or fruit they should be aware that many of the cheaper ceramic pots on the market may well be suspect in this respect even if they have white interiors, as one of the cheapest ways to get a white glaze (if you are ignoring health concerns) is to use lead oxide.

More about the kinds of metals used in glazes: high-fire stoneware glazes that produce blue glazes, for example, often contain cobalt, derived from cobalt oxide or cobalt carbonate. Many other high fire glazes make use of other metallic oxides and carbonates that may be fine for decorative purposes, but probably are not a good choice for growing fruit that may be eaten, or may simply be bad for the health of the plants inside them. Some of the metal oxides and carbonates used to produce glazes include various iron-oxides (generally safe), lithium carbonate (and many lithium-bearing minerals), various copper oxides and carbonates, manganese oxide, chrome oxide, nickel oxide, strontium carbonate, tin oxide, tintanium dioxide, and vanadium pentoxide.

It gets worse: Colorful low-fire glazes, such as those found in majolica and earthenware (including much cheap pottery probably being currently produced in China, and elsewhere, in earlier times) are also frequently based on lead oxides. If used for decorative purposes, or for serving up a plate of whole fruit, such glazes are effectively harmless, but I would not recommend growing food crops in them. Lead is notorious for leaching out of glazes.

Interestingly, when production potters manufacture pottery intended for food use, they either use approved formulations of glazes, or if they use custom glazes they should test their glazed ware to see if it leaches unacceptable levels of harmful substances. The test typically involves exposing pieces of the pottery--like bowls and plates--to an acid solution in an accredited laboratory, since acid accelerates the leaching out of the metals from the glaze. As citrus prefer acid soils, they would in theory be more at risk to this kind of leaching than plants that are grown in neutral or nearly neutral soils.

In other words, growing a citrus tree in a glazed ceramic pot is potentially a bad idea.

Interesting information Cebury. Would planting the citrus in a clay or plastic pot and then placing it in the ceramic pot as a cache pot side step these dangers?

Cath

Cath: Yes! Then you would just face the other downsides. If you have a great looking ceramic pot this is a great way to use it. Just make sure the drainage holes work--I might elevate the plastic pot by an inch or so using stones.

The more alarming dangers I've outlined would be very "hit or miss" since some glazes would be quite stable and others less so and in any event it would probably take years for much to happen. The problem is that it would be hard to tell that something was happening until the damage had been done.

A couple key differences between "stoneware" or high fire ceramics and earthenware or majolica ware are also worth noting: stoneware is clay that is high-temperature fired to the point it becomes glass-like or vitreous. It is then completely impervious to water. Low-fire pottery like the latter two forms of pots are much more prone to chipping (and are not at all frost-proof, since they are not vitrified, though their response to freezing should not be an issue when they are used to hold citrus trees!).

Since I see you are in zone 6a like I am, I will point out a couple more facts. First, even a stone-ware pot can still shatter from freezing if it somehow is filled or partially filled with water that freezes, or a root-ball that freezes,since earth and water both expand when they freeze. Low-fire pots can crack in the same way, but they are also prone to chipping. In part this is simply because they are softer than stone-ware, but there is another reason: if an earthenware pot is not completely glazed, inside and out, it is not waterproof since the unvitrified clay is still in effect porous (like a regular clay pot). A crack or chip in the glaze of such a pot is a weak spot where water can enter. If this happens, bits of the clay can absorb water, which then freezes and causes that bit to pop off. These problems will be worse if the water in question is hard, since the salts in the water will end up concentrating in the clay.

Lastly, I have various largish (up to two feet high) ceramic masks hanging about in my yard. While the stoneware pieces have survived several winters here in Connecticut, the glazes on them have in a couple cases either weathered a bit or flaked a bit due to the freezing and thawing cycles. These changes are mainly the result of the particular glazes I used (much more decorative than functional!), but they are always a possibility, since the way glazes "fit" on or bond to the underlying clay varies.

I love the diversity of people on this forum! We have people like Don and Al, the ultimate specialists whose education fits perfectly into their hobby, and are nice and willing to share their knowledge with everyone else. Then there are people like Mike, who have so much experience, and whenever someone is faced with a problem, they have likely had it before, and ready to save you much labor to save your tree. Then there are people like me, utter noobs who are trying to keep their trees alive : )
Andrew

Thanks a lot, Don_in_ct, your post was very educational and made me understand why I should avoid ceramic pots for edibles. I had suspicions that they were not acceptable, hence I started the thread. Now I wonder if it is good to avoid them completely, even for annuals because the water is going to leach from them into my yard every time I water my plants!
I am very grateful that you took the time to explain how acid leaches out metals from the glaze and about the heavy metals used in the glazes. Every single ceramic pot that I found in the nurseries are imported and the country of origin of these pots makes me sure that they definitely might contain Lead and the plethora of other heavy metals you mentioned!
I thank you for your time and effort and the help in educating us on this topic.
Meyer_mike, thank you too for your input.

I wouldn't worry too much about using your pots for ornamental plants. Your water is probably close to neutral, so it is not likely to leach out much from the pots. Because citrus actually want to grow in an acidified soil, they would be more likely to cause things to leach out of the glazes. In other words, it is the acid environment that is a concern, but even then only because you might eat the fruit.

I have a couple bonsai-style Jade plants that are growing in containers I made and glazed with a black high fire glaze that contains a lot of different metals. And some of my ceramic masks, which hang about in the back yard, have a "bronze" glaze that is based on manganese dioxide. These are relatively stable glazes, but I suspect a small amount inevitably leaches out and washes into the soil over time, but it would not be enough to worry about in my opinion, and it probably would only ever amount to what are called "trace" amounts, which are actually helpful. I wouldn't use the bronze glaze for plants, however!

We always have to be at least a bit reasonable about risks: for example, many homes have decks and landscaping features made from the older 2004 and earlier pressure-treated lumber which has arsenic in it (the newer treated lumber does not), which does leach out over time and can in theory be taken up by plants. I wouldn't want to grow veggies in a bed lined with that material, but I suspect many people do and will never have a problem. The main way you get the arsenic into you from the wood is by ingesting it, so that is a bit unlikely for most of us, but kids whose playgrounds made use of the wood did show some contamination in a study.

Your comment about the origin of your pots makes me feel better about being so emphatic about the citrus: none of us can really say just how stable the glazes are in these pots unless they have been tested, and I doubt that has happened. Back in the early 1990s I worked for World Precision Instruments, a research company that manufactured high tech equipment and also resold various bits of complementary scientific apparatus we purchased from manufacturers in China, and it was clear to us then that the Chinese were not especially concerned (to say the least) about environmental matters. Subsequent recalls of crayons and toys and baby formula have tended to make me think this disregard for safety has not changed. Therefore, it seems reasonable to be cautious where ceramic pots and food crops are concerned!

Thank you, don! I was trying to not mention that country's name in case I offended some one - but since it is out in the open, yes, I found most of my local high end nurseries carrying ceramic pots from the country that made tainted baby formula and pet food while my local Home Depot carried Italian made ceramic pots - go, figure! I have a learned a lot from you and thanks for helping.