Fertilization of cacti

[eccentro]

All you seasoned cactophiles post your latest fertilization method and schedule here. My garden is young and I would like to get a few helpful hints to get it thriving. Which type is best (% npk), dry or wet application, when and how often to apply, signs of over/under appllication, etc.

[Glider]

If the cacti splits open, you over did it.

-G-

[JRL]

True, bot trichos can take a lot of food and watering if they got sun and heat. You can pump em like watermelons and be amazed.

[eccentro]

Is an even composition of npk like 20/20/20 good? Or should it be weighted another way?

[Amomynous]

True, bot trichos can take a lot of food and watering if they got sun and heat. You can pump em like watermelons and be amazed.

This is true. I've had T. cacti that I've treated like watermelons, and they did fine. I used to spray them directly with fish emulsion. I don't even know if it is possible for these cacti to feed foliarly, but they didn't know either and seemed to respond very well to it!

[Glider]

On general principles 20/20/20 (10/10/10) is good for growth.  Weight the first one (nitrogen) even heavier if you want to see how far you can push growth of any given plant.

Remember that the composition of the fertilizer is important as well.  Not all nitrogen sources were created equally, ditto on potassium and phosphorous.  Faster absorbed (faster acting but also shorter lasting) nitrogen sources like ammonia (ammonium nitrate, ammonium sulfate) triggering faster growth but requiring more frequent applications.  Urea (carbamide) is a little slower as it needs to be converted to ammonia (enzymatic) then an ammonium salt (react with water, usually) before it can be consumed.  Nitrogenous composts provide an even slower but longer lasting effect.  I think, but can't quite remember, that nitrogen heavy composts tend to run acidic.

If you are looking to optimize your chance of seeing flowers you might want to look for something with a larger relative middle number, as phosphorous is typically associated with triggering/assisting flowering.

Also bear in mind that the number are percentages, and the relation between the numbers is important.  Thus the difference between a 20/20/20 (miracle gro) and 10/10/10 (many lawn / farm fertilizers) isn't so much the job they do as it is the concentration of the chemicals in the ready-to-apply mix.

I personally, for cacti, would look for a slow release fertilizer, and shy away from miracle gro.  That is unless you are growing trichos.  As noted above, trichos (and I think to some extent all columnars) are a different animal.

I wonder if the shape of the cactus doesn't say a lot about the growth habits in general?  Taller cacti reaching higher, out competing their neighbors in the way that a fast growing tall grass or tree out competes its neighbors, where as slower growing ground hugging globe cacti / short grasses tend to make their livings by capitalizing on territory where no one else is able to survive?

Best wishes,
-G-

[Glider]

You know, I've got to say this.  When I first read the title of this thread, I assumed you wanted to know when / how to pollinate (fertilize!) the cactus flower to optimize seed production.  Silly me.

Hit it with a q-tip as soon as the pollen starts to fall.  Don't trust the flowers to be self fertile, store the pollen in sealed containers at room temperature in a light-tight area for up to two weeks.  Brush the pollen from the stamens in one flower to the pistil in another flower, preferably on a different plant.

There, I said it.  I feel better now.

-G-

[eccentro]

Thanks for the comments guys. Great tips! I will change my methods accordingly and tweak them as I go. Thanks G for the detailed info. As you guessed..I am asking about 'feeding'. I have never even seen a tricho flower in real life   .

[Glider]

The blooms are huge, and beautiful.  I have only rarely seen them bloom, and never on a cacti less than 3 or 4 feet tall.

[JRL]

Glider thanks for the cactus porn!!!

I have used miracle gro in the past. Someone asked about making em pup. Well MG does that in spades.

I think if you force the trichos too much it compromises their hardiness a bit.

[JRL]

Oh yeah as far as blooming: if you take a cutting from ma mature bloomer, yiu might get blooms quite a bit shorter than 3 ft.

[dogbane26]

Ok this may seem unrelated but it isn't off topic.  

Is it also true that Trichocereus spp. can tolerate more water than other cacti?

I live in Florida and sometimes can't help my plants getting overwatered from rain water.  

The problem is I am not always home so can't take them off the ledge of the balcony which gets the most sun.  

The species I am growing is: T. bridgesii and they are small seedlings right now.   They are past the hard to see areole stage and its quite easy to tell they are true cacti. ( Just giving you an idea of their age)  

I am assuming Trichocereus cacti are well adapted to growing in North Central Florida since the temps rarely get below 15 degrees and even if so the duration isn't for long.

[JRL]

Small as they are, maybe too much water won't be good. But when they get established, go for it.

15 degrees is pushing it. You can put paper cups on the tips when it gets frosty, that is the most vulnerable part.

Still at 15 you might lose some stems , but I bet the roots will be just fine.

[dogbane26]

I think T. bridgesii and most Trichocereus cacti would do well here in Northern Florida.

Actually getting temperatures in the 20's isn't too common but they can occur anytime during January-March.

This winter we had 12 days in  a row January with nighttime temperatures at or below freezing(32 F) for a certain amount of hours.  

I emphasize in a row / consecutive because that is uncommon here.   12 days spreaded throughout the whole month isn't surprizing but in a row that is not usual.  

I believe that Gainesville/Alachua Florida is the cut off line between the temperate and subtropical zone.

This winter Gainesville could be considered a warm temperate climate but most years it is subtropical climate and the ocean moderates the climate here.

That is why you can get a week of 70's in January.  

The freezes here are still short lived and even if it gets to 17 F it might only last for not even 30 min and soon it will be 20, then 30 and by 10am back up to 40 F.  

Freezes will still kill delicate tropical plants but when I visited this botanical garden here the Catha edulis looked almost dead but Camellia sinensis seemed fine and still green.

Although this winter was colder than normal it still didn't get to below 40 until after 11pm.    We had a week where the highs were in the 40s and one day the high was 36 F.   Obviously that day you should cover or bring in tender perennials and other plants.

This winter was unusual for even North Central Florida. It definately set a record.

Hoodia gordonii is said to be only hardy to 28 F but that is my only plant I left outside when we had that cold week and they survived.

All 3 of my Hoodia plants survived the freezes.   17 F one night I heard.

[dendro]

I've been growing trichs in Hawaii for over twenty years, so I know something about trichs and rain.

Bridgesii doesn't like rain! They get black rots and die. I grow Tb's under roof or plastic. Pachs handle better, but still sometimes get the black spots and spores. Perus are the most resistant, and seem to handle the rains better.

I've grown the pachs up to six feet and flowering. But they don't like wind, and usually blow over when the wind comes up. Especially if there has been a dry, then a rain, then a wind. Cuz they get like soft, and snap as they lean.

Sunburn is also a potential problem in tropical places, especially if any part of the stem is exposed horizontally to the sun. Plus, as they age, trichs can get the thick beige plaques on the skins.

I've moved all cacti under plastic now. The weather and wet is just not worth it.