When to Use Liquid Fertilizer

[Aichybatoal]

So I know that you're encouraged to fertillize a cactus once a year for maximum growth. But I'm not going to use the standard "pellet" fertilizer, like Osmocote. I added some of that to my original soil mixture, and it's probably done its job already. So, I bought some Schultz Cactus Liquid Plant Food to use instead, because that'll be much easier to apply.

Liquid Cactus Fertilizer.jpg (41.1 KiB) Viewed 4461 times

Anyway, it says on the box to use 7 drops per quart of water with every watering, or 14 drops per quart of water once a month. That's fine, but I need to know how this translates to the "fertilize once a year" rule of thumb. In other words, how much of this liquid fertilizer should I use, and when? Should I obey the box and use it with every single watering (in the Summer only, obviously)? Should I obey the box and use it once a month (in Summer)? Or should I use it just once a year? Thanks for your thoughts.

[Saxicola]

Who is telling you to only fertilize once per year? That is outdated information. I would fertilize at least once per month during the growing season. Go ahead and use it every time you water if you like. The level of nitrogen in that fertilizer is so low that it would be nearly impossible to over fertilize as long as you follow directions.

[Aichybatoal]

That's really phenomenal information; thank you very much. But even my largest cactus can't even absorb half a cup of water at a time, and this says seven drops per quart. To water my cacti, I fill a measuring cup full of water, and just pour it in, let it drain, and repeat the process several times to saturate the soil. Is using this fertilizer as simple as doing a ratio and just using 2 drops per cup?

[tudedude]

yeah just do a ratio.

[DaveW]

Really it depends what you grow your plants in? If in soil based composts and you re-potted regularly (once a year) you did not need to fertilise cacti at all. If you left them longer in the pot, then once or twice a year was usually enough. However the trend for soilless composts now means they are being grown virtually hydroponically with little or no actual feed in the potting medium, therefore as Saxicola says you then need to fertilise frequently, but also occasionally leach the soil to avoid salts build up since the plant does not extract every element from the fertiliser in equal proportions.

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It's always safer to under fertilise than over fertilise though. Also you should always water so water runs freely out of the drainage hole at the bottom of the pot every watering, since this helps to flush unwanted chemical build up out of the pot. When it rains in habitat it really buckets down so flushes away any salts build up, but the soil drains quickly.

[iann]

They'll survive if you only fertilise once a year, but you'll get better healthier plants if you fertilise more often. Although too much nitrogen is a common problem, you can over-fertilise with other nutrients too. The effect are slower to show up, but more subtle and difficult to spot, and harder to reverse, so don't assume more is better. You also don't need to fertilise plants that are in fresh soil since there will be plenty of nutrients.

You probably don't need to water your plants several times. Just pouring water on once should be enough. Details depend on your soil, pot size, and growing conditions, so don't make radical changes if everything seems to be working for you.

[Aichybatoal]

Alright, thank all of you for all the advice. I'll be careful not to overuse it!

[Saxicola]

I think it will be hard to overuse it unless you go crazy with the stuff. Though DaveW makes a good point that a periodic leaching of the soil is good to wash out salt buildup.

One thing to note about your comment on pouring the water through several times vs. just once, is that while you only need to pour it through one time it is important that your soil is getting wet. Depending on your soil mix (it is especially bad when peat is involved) you can pour a ton of water through the pot and hardly any soil will get wet. So make sure your soil really is getting wet. The best way to do that if you are growing indoors and using saucers is to let water sit in the saucer for an hour or so after you water it. That should give soil enough time to uptake the water but not long enough to hurt your plants. Again, this is only an issue if your soil doesn't like to wet. You have to figure out for yourself if that is happening.

[Aichybatoal]

When I first got my cacti, I got suckered into buying some pre-mixed Cacti and Succulent Soil Mix, "specially formulated for cacti and succulents." Well, that stuff is straight from the pit, as we all know, so as quick as I could, I made a great big mixture of a soil mix reccommended by Daiv himself on this forum (50% pearlite, and the rest taken up by plain potting soil, coir, bone meal, and Osmocote) and repotted everything with that. Using coir is a great substitute for peat, because it's nice and light and airy, but it does absorb water, and it decomposes very slowly over time. This soil has much better drainage so it doesn't leave roots as succeptible to rot, and it actually absorbs water and can be re-wet easily, unlike that OTHER stuff... Anyway, that's the soil I use, and it seems to be doing a great job. The way I know that it does successfully hold water is I actually measure how much water I pour in, then measure how much comes out. After a single pour-through, my larger cacti can absorb up to half a cup into the soil. Then I just recycle that water and pour it in again multiple times. I realize (and have noticed) that each extra pour-through does nearly nothing to saturate the soil any more, because the amount leftover decreases by only a miniscule amount each time. But I still do it just to make sure that as much water has been absorbed into the soil as possible, and there are no dry areas left inside the pot. Now I also know that too much water leaves the plant succeptible to rot, but I NEVER allow stagnant water in my pots. The only water in the pot is contained in the soil, not pooling at the bottom.

ANYWAY, yeah, I collected a huge amount of rainwater recently, fertilized the whole batch (7 drops per quart), and have been watering my cacti like I described twice a week, and will continue this until September or so. Along with tapering watering off, I'll also stop using fertilized water so as to avoid poisoning them while dormant.

[Steve Johnson]

I collected a huge amount of rainwater recently, fertilized the whole batch (7 drops per quart), and have been watering my cacti like I described twice a week, and will continue this until September or so. Along with tapering watering off, I'll also stop using fertilized water so as to avoid poisoning them while dormant.

Okay, using a small plastic pipette (same as a medicine dropper) I measured out 7 drops and got 1/8 tsp. per quart. Oddly enough, the Schultz people have that part right when we do the math and get a dilution of 1/2 tsp. per gallon of water. Same as what I'm doing with my Dyna Gro All-Pro 7-7-7. Where they have it wrong is the Nitrogen -- too low for healthy vegetative growth in cacti. Bear in mind that a much higher ratio of P and K can actually inhibit uptake of N. Probably not much of an issue over the short term, although I'd be concerned about how well your cacti will be doing over the next 5 years or so if you stay with the Schultz fert. If you're interested in pursuing the Dyna Gro 7-7-7, check out your local hydroponic supply shops and find out if you can get it by the quart. (I could only find it by the gallon online. Pretty expensive at that price, although IMO definitely worth springing for a gallon of the Dyna Gro fert unless you plan on keeping a really small collection.)

Because I grow the vast majority of my cacti in a soil-less mix, I have to fertilize every time I water. Since you have soil in your mix, you can skip the fert from time to time since any nutrients that haven't been taken up by the roots are held in the soil. When you water with plain old H2O, the residual nutrients are released back to the roots. No hard-and-fast rules on when to skip, so I wouldn't worry about that. Flushing your pots once a year in the growing season is a good idea to prevent fertilizer salts from building up. Once again, plain old water. The procedure is to drench the mix so that the water is draining out the bottom of the pot like a faucet. Then do the same thing again an hour later. Gardeners recommend flushing a 3rd time, although that applies to non-xeric plants, so I'm not sure if you have to go that far with cacti.

Just my 2 cents on all this, so I hope you'll find something helpful here.

[Aichybatoal]

I sure did find things helpful! Thanks a lot - I'll look into that other fertilizer.

[Steve Johnson]

I sure did find things helpful! Thanks a lot - I'll look into that other fertilizer.

Glad to help. By the way, I did more searching online, and I couldn't find anything less than a gallon for the Dyna Gro 7-7-7. However, I was able to find 7-9-5 in different sizes at eBay here:

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While this is not the balance I prefer, the amount of Nitrogen should make the Dyna Gro 7-9-5 a much better choice over the Schultz liquid fert. (Honestly, I wonder if the Schultz people have actually grown cacti.)

Best of luck, and happy growing!

[Saxicola]

The Schulz people probably haven't grown C&S. At my local cactus and succulent club meeting last fall we had a representative from the people that make the Cactus Juice fertilizer come and give a talk. It was quickly apparent that he was a salesman and not someone that develops fertilizers, but more importantly, that they seemed to have no real knowledge of cacti and succulents. Cactus Juice is 1-7-6 and it was pretty clear to me that they based that on the very outdated notion that cacti needed virtually no nitrogen. When one of the people in the club with a lot of expertise explained that it is now widely accepted that higher levels of N are better for these plants the speaker seemed genuinely surprised to learn that. Obviously it didn't do any good as I still see them selling the 1-7-6 eight months later!

No matter what fertilizer you use just remember that the numbers are percentages and that it is proportional to the dosage they recommend. While it is best to just go ahead and buy the fertilizer with the percentages you want, if you have other fertilizer on hand you can still make use of it even if the N levels are very high or very low. Just use basic math (you can even use "maths" if you are British!). For example, if you use 14 drops of Schulz instead of 7 you have created a 4-14-14 fertilizer. Similarly if you had 20-20-20 fertilizer you could halve the recommended amount to create a 10-10-10. The only thing you can't do is vary the proportion of N-P-K relative to each other. So in the case of the Schulz you can't go too high on N before the P & K start getting really high.

[Aichybatoal]

These are all really good points, and I value all this fantastic information. I am going to stick with this stuff short-term, even if it is low in Nitrogen. It's not that important to me to have absolutely 100% perfect conditions for my cacti to grow in, but I am glad that I now have some great guidelines to follow so as not to poison them with P or K toxicity. And later, as in next Spring probably, I will definitely look into a more balanced fertilizer based on your thoughts. Thanks again!

[greenknight]

I've been using Ortho Liquid African Violet Food (6-9-5) on my cacti since cyclamen mites did in my African Violets. I don't think that's still available but Schultz makes an African Violet food with similar proportions, probably a better choice for cacti than their cactus food.