There are so many fertilizers out there, and I'm sure everyone has their favorites...but since you asked...I use the Dynamite Fertilizer(I buy mine at H.depot). It's safe for containers and is slow release. I've used the green, red, or purple container. Obviously the The Citrus/Palm formula would be the best but it is very hard to find. I also supplement with MG or Miracid(liquid) every 2-3 weeks at half strenght during the growing season, for me that's March thru Oct. This is what works for me, but I'm sure there are many suggestions out there!

Oops...Forgot to add a link to the Dynamite Fertilizer...

Here is a link that might be useful: Dynamite Fertilizers

I LOVE the "dynamite" fertilzer for citrus...It is a yellow bottle...
To me it is worth every penny and ordering if you can't buy it locally!:-)

AND

Along with that, a steady feed of Foliage Pro at every watering as suggested in the fertilizer thread by a very knowlegeable member....at 1/4 strength

Is this good for plants that need watering every other day during the summer? It gets hot and dry here in the summer and my small plants need water daily and the large ones need it every other day. I'm not exaggerating, they need it. Would it really last for 9 months? I'm trying to get my 23 year old potted grape fruit to finally flower this year.

This is not an easy question...I hope someone can chime in and help you.

How much and how often you fertilize can depend on the kind of soil you use..So lets us know what your soil consists of ok...

If your using a fast draining mix, such as Al suggests in the container forums, the gritty one in particular,most likely everyday feeding at weak doses and watering wouldn't be an issue.

What's is great about that mix, is that if the the weather or pots are too hot to allow the plant to absord the nutrients, they will never build up anyways. Every watering will flush what residue salts and unused fertilizer you have that can become toxic over time, to be replaced with fresh fertilizer and water.
It has been a wonderful soil for me in many plants.
My plants were VIBRANT all of my last very hot summer. I too had to water everyday..
I watered and fertilized mine last summer with a 1/4 strength of dynagro, and also had CRF in my soils, and they did marvelous!! I watered this way in the gritty mix and the 5.1.1.one, discussed in the container forum.
And our summers can get very HOT.

Please, take a peak on that forum. I think you will get your answers your looking for. It will take some time to read some though..lol
Here is the link to check it out. I hope it helps you...
There is alot of educated and expereinced members there you WILL learn from. Some have asked the same question as you too.

http://forums2.gardenweb.com/forums/contain/nph-ind.cgi?n=60
Fertilizer Program for Containerized Plants II

Mike...:-)

Try Mega Green or Multibloom. I'm here in Florida and have never had so many blooms as this year. It is a liquid organic fertilizer made from catfish hydrolysate. Apply it in a foliar spray at 6 oz per gallon od water.
Good Luck.

Here is a link that might be useful: Mega Green

Something to keep in mind regarding slow release fertalizers is the temperature. Certain brands do not do as well in areas with very high temperatures because some slow release formulas are released depending on the temperature. I am currently using Dynamite all purpose as I have heard it does better than Osmocote in areas w/ high summer temperatures. Here is a good link:

http://citrus.forumup.org/about3353-0-citrus.html

If you scroll through the posts I added a link towards the end of thread from the Washington State Department of Agriculture that also has a good breakdown of alot of products. The citrus growers forum is a great place for info as well, check out some of the other threads there!

Joe

The mix I'm using is pretty well draining. I can't remember what it consists of besides peat, maybe sand, maybe perlite. It probably had organic matter in it but I bet it's since broken down but I might amend it with more one I put my plants outside once it's warm enough. I'm not going to put in manure since these are house plants during the rest of the year and I don't want that in the house.

I've been told, for most plants outdoors in the summer when watering daily, to lightly fertilize twice weekly. I use Miracle-Grow or whatever else I have lying around. I also use epsom salts and Superthrive, some times.

I'm going to try 10 ppm of gibberellic acid to see if it can get flowers for me.

Sorry...
But what the heck is gibberellic acid?
OK.
Guess I will have to spend more time on google..:-)
When I find out what my local nursery used to get theirs to look as good as they do after a long winter, I will share.
Look at the citrus in the thread "encouragement for us cold winter" citrus container growers...

The owner likes me. That is a plus. I will find out....:-)

Gibberellic acid will not encourage the production of blooms. What it will do is set fruit on unpollinated blooms that are already present. The only group of plants I'm aware of in which it is the trigger to "flower" is pine trees (which of course don't really flower; they make cones) -- but it does stimulate that effect in them. In dicot trees, including citrus, it may have no effect at all at 10 ppm, and at higher concentrations, will actively prevent flower formation, if you apply it when the tree is not flowering. At very high concentration, it will completely inhibit flowering, and cause the tree to revert to juvenile growth (strongly upright, big sharp thorns, etc.)