You pose a great question but the answers are complicated.

I'm not convinced that the N-P-K ratio is that important. What kind of fertilizer are you using - liquid, granular, slow-release? Calcium and magnesium are macronutrients for most subtropical plants, so these need to be provided in the right proportions, along with the other micronutrients.

And if your goal is compact, colorful growth, it is better to be very frugal with your fertilizers. High nutrients result in weak growth.

For many species, just mixing in some topsoil onto the surface, or just repotting, is enough nutrition by itself. Only vigorous, tropical succulents like Adenium, large Pachypodiums and some pachycaul trees will benefit from additional fertilizer in the growing season.

So your list (Adro, Aloe, Stapelia, etc.) are probably better off without anything extra, assuming you repot every few years.

Thanks Xero.

That is certainly a very different answer than I expected :)

I have all three kinds of ferts: granular, liquid and control release. I also have a liquid and soluble micro fert, plus a 0:0:3 supplement.

Also, I don't use a commercial cactus soil. I have been buying my soil at a garden center that they make. But I am getting ready to start making my own soil mix.

When you say certain pachycaul trees will like some fert, would most of them be kinds that have a lot of foliage or not necessarily. I have several plants that I bought as "pachycauls"; Bursera microphylla, Ceiba parviflora, Petopentia natalensis, a couple Jatrophas and a couple Talinums. If these are true pachycauls or not I am not sure, and I very well may have some others I am not aware of.

Thanks again ^^

Ross

For the most part, if it is a tree it can be fertilized. Just don't over-do it. I don't grow the fat plants you mentioned so I'm not sure if there are some that particularly enjoy high fert. Often, open root run will do more to stimulate lots of growth than extra nutrients.

Unless you have identified a specific nutrient deficiency, how would you know you need something like a 0-0-3 supplement?

I personally like the slow-release granular types only because it's easier - you apply once and you're done. But good quality liquid ferts are great. It's important to leach out the salts that accumulate in the pots. Every now and then drench the pots so that a lot of water comes out the drainage holes. Luckily most succulents can tolerate high salt levels but it's still better to keep things in check.

I think this is being made unnecessarily complicated. I grow indoors only, but grow lots of Succulents (Aloes, Haworthias, Gasterias, Euphorbias, Sans, Crassulacaes, etc.) I consider all their 'leaves' to be foliage.

I used to pay attention to lower nitrogen fertilizer (using something called Cactus Juice, I think it was 2-7-8). Nowadays I use a balanced fertilizer for almost everything, including the Succulents. I think the key for them is not to fertilize them too often (no more than 2-3 times per Summer).