Question
I purchased a blood orange tree a month ago.  I have it in a very large pot outside.  I live in Florida.  The tree now has many blooms and some fruit starting to develop.  What kind of fertilizer should i be using and how often?  I also have an avocado tree, what should be used for that and how often?  Thank you for your time.

Answer
Because these are subtropical plants, at least some Blood Orange cultivars require a cold spell during winter to develop their distinctive red flesh.  During the peak growing season, temps should range from 55 to 100 degrees F.  Some are more productive than others.

These are in case you didn't know EXTREMELY popular around the Mediterranean -- unlike here, Blood Oranges represent a third of the Orange Business over there.

The alkaline, Calcearolous soil in Florida does nothing to enhance the red fruit color, but it does not seem to alter the flavor at all.

Overwatering, however, will dilute the flavor and produce bland, sour fruit with little juice; less watering produces richer orange rinds.  According to the Purdue Cooperative Extension Service (http://www.hort.purdue.edu/newcrop/morton/orange.html), 'The best soil for orange-growing in Florida is known as Lakeland fine sand, well-drained, and often identified as high hammock or high pineland soil.'

Purdue speaks extensively to the nutrition needs of this plant that may be useful: 'Extra Nitrogen increases the peel oil content of oranges, while extra Potassium decreases it.'

They note that in California and India, studies found the best Oranges are found by supplemental feedings of Nitrogen.

The California Society of Avocado Growers (http://www.avocadosource.com/CAS_Yearbooks/CAS_30_1945/CAS_1945_PG_065-070.pdf) has prepared a complete sheet on cultivation of these tasty plants, 'Fertilization of Avocados'.

I confess not to having grown these myself -- not past 2nd grade at least, and certainly not to the point where I could harvest Avocados -- but I do know that generally the younger potted specimens are inclined to burn when left in direct sun, and they tend to grow quickly, into rather large plants.

Their delicate root systems are susceptible to root rot and care must be taken to make sure they drain properly.  Do not fertilize in winter.

Thanks for writing.  Any further questions, I'm here.