Are those only old, bottom leaves that are yellow? If so, then that is normal. I am concerned about your soil because it looks like it holds a lot of water for too long. What is it?

It's a mixture of old and new leaves turning yellow. The soil drains pretty well... its Dr. Earth Organic Fruit Tree Mix.

Star Ruby while an excellent very sweet very dark red grapefruit usually dies young from foot rot or other diseases. Here in Florida 9B I've never had one live longer than 5 years. It's too bad because they are one of the sweetest and darkest red grapefruit varieties.

http://www.citrusvariety.ucr.edu/citrus/starruby.html

Was your Star Ruby in ground or pot nighthawk0911?

I too am worried about the mix it's in. How long has it been growing in that pot without a re pot? What kind of mix is that?

From Univ of Cal site.

"Compared to other grapefruit varieties, Star Ruby is more difficult to grow well. It has exhibited greater susceptibility to phytophthora, nutrient deficiencies, cold temperatures, and pest problems. It does not appear to grow as vigorously as other grapefruit varieties, and the fruit is often smaller. "

Texas Red GF growers have totally abandoned Star Ruby in favor of Rio Red due to the problems with Star Ruby. Rio Red is almost as dark as Star, but not quite. Whether it's as sweet as Star Ruby I don't know. Any red GF you get from Texas called "Rio Star" is Rio Red GF.

In Florida most Star Ruby GF trees die within 5 years according to my citrus nurseryman and that was my experience as well and my trees were mature in ground trees. I wouldn't recommend anyone getting Star Ruby. Ruby Red & Rio Red are better options.

Could be normal or could be a minor nitrogen or other deficiency. Trees in pots are probably more susceptible to nutrient deficiencies and citrus are heavy feeders. It doesn't appear to be HLB, CTV, Blight or any other major citrus disease so just add some fertilizer and get some sleep. That's about all you can do anyway.

One would think that Citrus in containers verses the ground are not suceptible to the same issues...You are also right to be concerned..Your leaves should be a much richer green that than that.

Mineral Deficiency

When the citrus tree is not getting the proper nutrients, its leaves can begin to yellow. Nitrogen deficiency shows as light yellow-green leaves with veins slightly lighter than the foliage. New leaves are smaller and thin, and mature leaves begin to develop mottled, irregular yellow blotches. This yellowing can cover entire leaves, which then fall from the branches. When the citrus tree has a magnesium deficiency, yellow irregularly shaped blotches appear at the base of the leaves growing close to the fruit. These blotches will enlarge and eventually cover all but the tip of the leaf. Leaves retaining their greenish color will drop when the tree is water stressed or the weather turns cold. In soil pH levels below 5, use dolomite to raise the pH to between 6.0 and 6.5 and increase the magnesium readily available in the soil.

"Because each species of citrus tree has its own specific fertilizer balance requirement"

I don't believe the above statement is correct. Do you have any research to back this statement? - Silica

I don't belive that either. Some are hungrier sure. But Malcolm manners was very clear that they all have the same requirements. Unless I read what he wrote wrong.

any and all deficiencies between plants who are fed the same are from differences in absorption due to ph, ppm and nutrient lockout.

I copied it over from another site - not my words.

It's not a magnesium def. Mag Def leaves a "V-shaped" pattern in the leaves. I think it just needs a nitrogen boost.

The potting soil is Dr. Earth Fruit Tree Mix (http://drearth.net/products/organic-soils/natural-wonder-fruit-tree-planting-mix/)

The tree has only been in the pot for 6months.. It currently has 3 GFs.

Thanks all for the input.

Haku, I am concerned about you using that soil because it seems to me that it is very water retentive and might cause root rot which is a common problem that citrus have with water retentive soils. I know that the website says it is OK for citrus but I have my doubts.

I agree with Vladimir about the mix. Search for 5-1-1 mix or gritty mix and perhaps switch it to that.

By the way, because you are using Dr Earth which has no GMO's I thought you might be interested to know that the Ruby Red Grapefruit is a genetically modified organism (GMO) obtained by irradiating the parent tree with ionizing radiation to cause genetic mutations.

@Vladimir - Star Ruby was created by irradiating a Henderson GF. RUBY RED WAS A NATURALLY OCCURRING SPORT OF PINK GRAPEFRUIT. Many Red grapefruit varieties lose color the longer they hang on the tree late in season. The goal is to find varieties that are redder/sweeter and hold their color.

Technically any man made hybrid or cross is a "GMO", I think people make too big a deal over it. Nobody has died yet or gotten sick yet from eating Star Ruby GF.

Nighthawk, I am referring to Star Ruby, not Ruby . Here is a reference: http://www.citrusvariety.ucr.edu/citrus/starruby.html. By the way, I do not swallow the ant-GMO and other crap that Dr. Earth preaches and I would never buy his products.