1) Most citrus do best in "Mediterranean" climates, ie, Italy, California, etc. This means their optimal temperature is from 24 C to 30 C. But they will grow in a much wider range. The research I have seen says the minimum is about 12.5 C and max is around 39 C. SO, the 20 C should be fine, 10 C not so much. 2) Yep, citrus have been grown in pots for centuries. 3) In my experience sudden changes in any environmental conditions (light, temperature, or water) and the citrus rebel quite strongly with leaf drop and general pouting for weeks to come. It's best to slowly move them in doors or out doors over a period of several weeks; gradually increasing their exposure to the target environment. Even still I always get some leaf drop. 4) As long as you don't burn the leaves with super strong concentrations they don't seem to be that sensitive to sprays. 5) Citrus roots need plenty of oxygen and room to breathe. It's an absolute must that the soil dry slightly between waterings or the roots will rot. There is even a special soil mix many on this forum use to try and prevent over watering.

Meyers have thorns. The large thorns and larger than typical leaves on the new branches are what we call watersprouts; they usually indicate that you are being a bit too kind to your tree in terms of food and water. Not to worry, just prune them back to the general level of the canopy and they will revert to normal growth. A mature Meyer will normally have maturing fruits, small fruits, and flowers all at the same time and will produce fruit nearly the whole year.

I agree about the general lack of knowledge about soil relationships, even in some frequent posters, but in my case I try not to make the assumption they are locked into using a soil that is bound to create root issues AND that restricts them to slowly increasing pot size incrementally. People like learning new things and discovering there are viable alternatives to staying stuck in the mud some try to grow in. ;o) I explain the alternatives & why they will work better, then let them decide. Understanding soil relationships to plant material is important to being able to grow plants to our best potential. You mention you understand the concept, but I notice you skirt it. There is no one soil that will always be appropriate for a given plant in all situations. As cultural conditions and even things like pot size vary, so should the soil mix. It's far better to at least enlighten folks to that fact. Even if they don't USE the info, it will provide a puzzle piece when difficulties DO arise. As evidenced from the amount of mail I receive, people do wish to learn more about soils. Those that I have helped here & off-forum, usually settle on their own mix, based on what's available to them and what they are willing to invest (time, primarily) in the soil. Invariably, they settle on a well structured soil that retains that structure for the life of the planting and that holds good volumes of air as long as it's in use. I'm not out to get you. ;o) When people tell sad stories of rotted roots, is it more appropriate to tell them to reduce pot size, or to grow in a more open soil? No need to answer, it's rhetorical. Al

Burggril, Lazz is certainly correct. You should choose a fertilizer formula as close to a 5-1-3 ratio as you can find. The reason is because, 5-1-3 is the ratio that citrus trees absorb nutrients from the growing medium. In other words, for every 5-parts of nitrogen that the tree's root system absorbs, it will also always absorb 1-part of phosphorus (P2O5), and 3-parts potassium (K2O). Nitrogen and potassium are very water soluble, and can be easily leached from the container if over applied. Phosphorus is not very water soluble and it will build up in the soil. The 30-10-10 you mention in your thread is, of course, a 3-1-1 ratio. Actually, it is not all that bad, but is low in potassium. Potassium is the nutrent that aids with the general over all health of the tree, and also helps in fruit size. The other fertilizer you mention 12-7-5 I would not recommend. Of the three major fertilizer nutrients N-P-K, citrus trees use the least amount of phosphorus. Therefore, phosphorus (the middle number in fertilizer formula) should be the smallest number in the fertilizer formula you select. Also it is very important to choose a fertilizer that contains trace minerals. When you water the tree DO NOT apply small amounts of water at a time. This will lead to a serious problem called "High Soulble Salts". When you irrigate the tree apply enough water to the soil surface, so that at least 20 percent drains out the bottom holes. Good luck. Take care. - Millet