Favorite fertilizer brands?

[EliWhitney3140]

I am sure this is a topic that has been discussed on this website many times but I could not find a thread specifically about it. Do any of you have any brands you swear by? I would like to do as much research as I can before the growing season.

[MikeInOz]

The brand is not important. The analysis is.

It should have at least the same amount of K as N but preferably more. It should have moderate P. It should have Ca if you use rainwater or do not supplement the mix with gypsum and or limestone and or crushed shells. It should have all the trace elements particularly if you use no organic matter or soil in your mix.

In other words look at the analysis and mix two or more different fertilizer brands if necessary until you get what you need.

[MikeInOz]

Osmocote has just released a cacti and succulent formulation. For once I can say that it is GOOD! I'm already using it.

https://www.bunnings.com.au/scotts-osmo ... lsrc=aw.ds

[Steve Johnson]

I am sure this is a topic that has been discussed on this website many times but I could not find a thread specifically about it. Do any of you have any brands you swear by? I would like to do as much research as I can before the growing season.

That's easy -- Dyna Gro All Pro 7-7-7. Unfortunately, it's also expensive for people on a tight budget since it comes only by the gallon. Their Orchid Pro 7-8-6 comes in smaller and more affordable quantities on eBay. Here are the nutrient profiles for both:




Dilute at half-strength, which is 1/2 teaspoon per gallon of water. The only problem with the Dyna Gro ferts is if they're allowed to freeze during winter when they're kept in the garage or a garden shed. When that happens, the Potassium salts precipitate out and crystallize. Getting them back into solution is a big pain in the backside, but the ferts are perfectly safe to keep in the house -- problem solved.

K needs to be 1.5 times higher than N, so the Dyna Gro ferts on their own don't have the right N-to-K balance. We can address that with the addition of Potassium sulfate, available as a powder in 3.5 oz. packets on eBay here:

https://www.ebay.com/itm/Potassium-Sulf ... SwAbxebYaY

For the 7-7-7, add 7/64 tsp. For the 7-8-6, add 1/8 tsp. IMO Dyna Gro ferts are the gold standard here in the US -- go with either one, supplement with the right amount of Potassium sulfate, and you'll be happy with the results. I grow the vast majority of my cacti in a soil-less pumice and granite gravel mix, so I have to fertilize every time I water. If you have soil in your mix, you won't have to fertilize as often, maybe every third or fourth watering.

By the way, shout-out to MikeInOz for teaching me about ferts. The Dyna Gro products contain a sufficient amount of Ca, and here's something I didn't know about until Mike informed us on something important -- the balance between Ca and Mg. 2% Ca and 0.5% Mg, that's the right balance.

Osmocote has just released a cacti and succulent formulation. For once I can say that it is GOOD! I'm already using it.

https://www.bunnings.com.au/scotts-osmo ... lsrc=aw.ds

Checked it out on Amazon and eBay, not available in the US (or at least not yet).

[EliWhitney3140]

Wow, thank you very much

[EliWhitney3140]

My soil mix is equal parts pumice, lava rock, akadama. I did purchase some crushed limestone that I plan on either mixing in with new batches or adding as a top dressing.

[EliWhitney3140]

I am curious how much you like to fertilize? You hear so many different opinions when you are starting out with any hobby. From what I had seen online many people wait to fertilize after the first water of winter dormancy. Some people only fertilize once a year. Any opinions on how much you should be fertilizing your cacti?

[DaveW]

You need to differentiate between growing in purely mineral mixes and organic ones of course and how often you repot into fresh soil? Most organic mixes probably needs no fertiliser if you re-pot yearly, but mineral mixes are virtually a form of hydroponics where the substrate is merely to hold the plant and nutrients need to be provided by weak fertilisation regularly.

Maybe an over simplification as even in mineral mixes some nutrients may be released by the substrate depending on its composition but they will run out of nutrients quicker than an organic mix.

[Shane]

That's easy -- Dyna Gro All Pro 7-7-7
[...]
Dilute at half-strength, which is 1/2 teaspoon per gallon of water
[...]
K needs to be 1.5 times higher than N, so the Dyna Gro ferts on their own don't have the right N-to-K balance. We can address that with the addition of Potassium sulfate[...]

So Steve, this would give us a 3.5-3.5-5.3 fertilizer all told? Or 7-7-10.5 diluted to half strength?

[Steve Johnson]

So Steve, this would give us a 3.5-3.5-5.3 fertilizer all told? Or 7-7-10.5 diluted to half strength?

Full strength for the Dyna Gro 7-7-7 is 1 tsp. per gallon of water, so we'll want to go with half strength. But there's a little more to it that needs some explanation (thanks again to MikeInOz for what I learned):

For reasons unknown to me, American fertilizer manufacturers go by a different standard than the rest of the world when it comes to telling us the actual amounts of Nitrogen, Phosphorus, and Potassium in their ferts. Diluting the Dyna Gro 7-7-7 at half strength, we'll use those numbers here. When you're putting 1/2 tsp. of it into a gallon of water, 3.5% is the actual amount of N. 3.5% is Phosphoric acid (P2O5), but the actual amount of P is 1.55%. 3.5% is Potash (K2O), but the actual amount of K is 2.9%. Expressed in NPK numbers, the true element values are 3.5-1.55-2.9. As I said earlier, K should be 1.5 times higher than N, so we need to bring the K up from 2.9 to 5.25. The Potassium sulfate I get is 0-0-52 -- add 7/64 tsp. to the gallon, and the total true value of P is 5.25. Voila! Sulfur deficiency leads to pale-looking cacti, and the trace amount of S in the Dyna Gro ferts doesn't cut it, so the S in Potassium sulfate is a definite side-benefit.

One thing worth mentioning...

I've seen a myth being spread at a number of places suggesting that some cactus species need a high-Phosphorus fertilizer to flower as well as they should. Nothing could be further than the truth -- in fact, too much P inhibits flowering, and it causes a number of other problems as well. P should be lower than N and K, so what I'm showing all of you here is a good NPK balance for cacti and succulents.

[greenknight]

You need to differentiate between growing in purely mineral mixes and organic ones of course and how often you repot into fresh soil? Most organic mixes probably needs no fertiliser if you re-pot yearly, but mineral mixes are virtually a form of hydroponics where the substrate is merely to hold the plant and nutrients need to be provided by weak fertilisation regularly.

Maybe an over simplification as even in mineral mixes some nutrients may be released by the substrate depending on its composition but they will run out of nutrients quicker than an organic mix.

Very good point.

I use mixes that are partly organic - summer humidity here is low, as I've mentioned before. I don't repot often, cacti spend 3 years or longer in the same mix. I fertilize once a year at most, often skip it entirely. My cacti grow and bloom just fine.

[MikeInOz]

For those interested, this is the Osmocote cactus and succulent analysis...(6 month)

P1140349.JPG (97.16 KiB) Viewed 2216 times

Good for me as I add 1-2mm gypsum to all my pots so that takes care of the calcium. You probably don't even need to do that if your water contains Ca. - and most do. (I use rain water) The only thing left to do (if anything) is to give a feed of straight potassium sulphate at the end of the season.
Might be worth contacting Scotts to see if they can supply it to US growers.