I would probably use terra-cotta for outdoor containers for reasons given in the article that follows. For indoors I would use plastic ones as I believe they offer more protection against potential moisture and compression damage to the flooring. Some types also slide easily on carpeting making them easier to rotate or to move around. Choosing a Clay or Plastic Pot for Plants (typeofpots) | Nebraska Extension in Lancaster County
Thank you very much for your reply! I do have my citrus in terracotta. I live on Vancouver Island so the climate is quite moderate. I overwinter them in my greenhouse and keep the temperature at 5 Celsius or above. The terracotta seems to stay very cold and I worry about the roots. I was told if I switched to plastic they would be more comfortable. I’m really not sure. I’m also considering switching to 5-1-1 soil to allow for better drainage.
I am not a fan of terra-cotta myself and only use plastic or equivalent. I keep my greenhouse just above freezing (lowest I have recorded was 0.25C, so pretty close!) and the citrus do perfectly well in pots at that temp, so the temp at 5C is not a cause for worry. Good drainage is definitely important. I have not used 5-1-1 soil, but my citrus have been perfectly happy when I used things like a coarse Sunshine mix. More recently I make my own mix. Citrus are heavy feeders though, so be sure to fertilize appropriately whichever soil or pot you use...
I use a commercial fertilizer now, not sure you could buy that one easily, but it is equivalent to Miracle Gro's regular formula (just cheaper in bulk). Miracle Gro works fine overall, but you may need to add a bit of calcium on rare occasion if using soilless mixes as they tend to run out. Adding calcium is easiest with Gypsum, but bone meal or lime works also. Be sure to read the label to make sure you don't add too much.
My plastic pots, even though they're indoors, become brittle over time because of exposure to sunlight. Wouldn't the problem be exacerbated outdoors?
Decent plastic pots have UV protection and last 10 years or so in my experience. That is usually longer than I like to leave a plant in the same pot and I often re-use old pots after cleaning and sterilizing them with bleach. It is certainly possible a cheap pot might not have UV protection and last less time but I have only noticed that on rare occasions ... but of course your luck may vary. Once the pot starts to get brittle they can go in the recycle bin. If concerned about lasting more than 10 years or so you could try fiberglass pots, which seem to last longer but are less flexible. Some of the fiberglass ones I have are already 12 years old or so and still seem fine outdoors.
Now that I think about it my pots last at least 10 years before becoming brittle. It's annoying when they it happens, especially since the ones I use are no longer available and suitable replacements are difficult to find.