The first place to look, in your job as plant detective, is the potting mix. Is it very coarse textured and fast-draining? Most commercial potting mediums are almost entirely peat, which can make them sludgy over a bit of time. Those potting mixes can cause over watering issues, as well as develop dry pockets from improper watering (little sips at a time).

Well, I see a few things that might be causing this. It looks like you've got a situation where you have a LOT of grass competing with both water and nutrients . You really do need to create a much large cleared area from underneath your little trees. Grass is a huge nitrogen hog. It will simply gobble up all that nice fertilizer you're putting down for your citrus. Not familiar with that particular fertilizer, but you'll want a fertilizer formulated for citrus, that is higher in nitrogen and also contains a good amount of micronutrients as well as your NPK macronutrients. And if your trees are being sprinkled by your lawn sprinklers, this is NOT good for the trees. This actually can eventually kill a small young tree. They don't like their trunks sprinkled. You'll want to put your trees on a drip system, and give them a long, deep drink one or twice a week (depending up on how hot it gets.) Doesn't look like sunburn, and yes, young citrus trees can get sunburned if you live in very hot, dry, sunny areas (like AZ, interior S. California). I agree with John's recommentations, fertilize at least 3 times a year - I fertilize 4 times a year - February through September/October. And, I use a foliar fertilizer especially if we've had a cold, wet winter and spring, which for me tends to make micronutrients unavailable since my soil is mostly DG. Grow More Citrus Growers Blend is a great product, and can be applied both to the roots or as a foliar spray. Spray in the evening. Patty S.

Ed, this is what I would do... You have a few options. Th first option is what I would do if the mix was too compacted and suffocating the roots. If you think it will get by, then options two and three would work fine. I would remove that tree from that soil into a better draining mix asap if compacted. I would use clay, a light colored ceramic or plastic pot. I would use a wooden dowel that checks for moisture deep into the root zone for all options. I would stick that tree in an area where it gets part sun until it gets use to its repot, probably into the shade. Summer time in a very hot area is the worst time to transplant anything, especially bareroot, but if it must be done, then it must be done. Once you use a pot that repels the hot sun rays and your tree has acclimated to a repotting, then your tree will enjoy full sun no matter where it sits... Although as Ken said, make sure the roots cool off at night in order to do proper photosynthes... Roots must cool at night and never over heat. They must have oxygen just as we do in a mix that allows that. Your second option? You could stick that plant, pot and all, into a bigger pot full of mulch that repels the hot sun rays..The mulch or other soil mix will suck the moisture from that pot away from the bottom encouraging it to dry down better and quicker.. This will prevent a 'pwt' in your container and will encourage your roots to stay cool until your repot come next spring. It will also help your mix to dry out and stay evenly moist. You should also flush the mix out at least once a month of accumilated salts with fresh water until you can change it in the spring. Option three...Use the wicking method after you have flushed your mix out... ****Use option one for sure if you feel that your mix is just too dense and compacted. MIke

Looks more like salt burn, or general nutrient deficiency. If you add some soil sulfur to your soil it will lower the pH; citrus thrive best in pH soils 5.5 to 6.5. You can add some gypsum to help the water uptake and retention for clay soil. Could be just a case of overwatering; but if it looks good in Spring after Winter rains that is less likely.