It's definitely a mutation in that stem, and it is pretty, but it could not be propagated separately from the parent plant as, producing no green leaves, it has no chlorophyll and is relying on that produced by the regular shoots to survive. Still, as long as the other shoots grow green leaves and photosynthesize, it should continue to grow, I had a similar mutation in a potted vinca vine "Wojo's Jem" where one stem sprouted and grew in completely white. It grew very slowly but survived for a few months as the plant still had green leaves to rely on. Eventually, it died out though.

A 3-4 inch layer of organic mulch under your tree will help keep tender feeder roots, which are close to the soil surface, cool and slow evaporation. Plus as it decomposes it releases nutrients back into the soil. Don't fertilize your tree until it shows some signs of recovery and then use light applications. It looks like there is a little new growth already so the worst may be behind you. Good luck. Here is a link that might be useful: Citrus information from the U of A

Its definitely not overwatering (i think), im very sensitive to the watering schedule and always allow them to just start to wilt, and i can see the medium turning a dry color at the top. I have a very low nutrient medium that ive custom made from scratch(mostly aeration). its kind of a cross between a 5-1-1 and a basic potting soil. Lotsa perlite, a little dolomitic lime, lots of orchid bark. The problem may be from a specific set of plants I repotted in a frenzy and I basically just used straight potting soil. I also planted some seeds in that particular batch of soil and it completely frapped out, perfect germination but stunted growth from the outset and turned all yellow. I believe it was "greenall" brand potting soil. total crap! I replanted all the seedlings into new MG seed start mix to hopefully salvage a few of them but im not holding my breath. About 20 varietals all barely putting out true leaves after 2 months. well see if those get any better. I have a HUGE amount of leftover GH flora series nutes that I have been using. they have been sitting for a few years. 15 gallons total, 5 gals each nute. Its possible that I overfertilized last week since I have so much its hard to get a "teaspoon" amount out of the 5 gallon containers. but Im pretty sure I got it right. @ottawapepper why do you use your nutes at 1/4 strength? ive read this elsewhere but im unsure why I would go that route if my plants are 2-3 months old? I figured this would require a fairly rapid uptake. Im currently growing around 300 pepper plants and about 40 varieties. all hot and superhots. Im running out of room in my greenhouse, Everyone asks my why I dont grow other plants, all i can say is I really like hot peppers! @habjolokia Hi Mark, thanks for the input. I have some supplemental light (led's that are very weak but designed for plant growth) that are more of an experiment than anything else. that is why some of my plants look purple. its the blue/red LED's. Eventually im planning on adding an array of LEDs to the entire greenhouse and then really trying to push my growing season out. So im curious what type of ferts you use Mark? any name brand? why not use the epsom salts? have you had any bad experiences? Im one of those guys who tends to overdo things so the less is more philosophy is usually very applicable for me.

Mary, I started using 1 capful of the FP container, recently, I went up to 1.5 capfuls...sometimes close to 2 for my Meyers and limes. I've not seen any ill effects. I do usually water with hose thoroughly before and then a while after, fertilize. I also add about 1/3 capful of vinegar. That is all I need because my water is already fairly close to 7.