What kind of data is your Koubachi Plant Sensor providing for fertilizers - are you able to post an image of what it reports? Normally sensors are providing mS/cm.

2-7-7 or 3-1-5 is not required for your Christmas Cactus, 3-1-2 ratio is fine. I have a bottle of Schultz cactus 2-7-7 and it's sitting unused in my cupboard for nearly 10 years now. I am using a 12-4-8 with micronutrients instead.

Unfortunately, I am not familiar with Cyclamen so hopefully someone else has some helpful advice for that.

For sure there is a lot of misinformation about fertilizer online and it can be difficult to determine what's truth and bunk!

I'm not familiar with cyclamens' needs but I've grown Thanksgiving (Christmas) cactus for many years. I used to make my own fertilizer with beer, ammonia, Epsom's salt, aspirin, and other things depending on how I felt. Then I went to Eleanor's VF-11 but I can't find that here in Tennessee. So I'm on the lookout for another something. Sometimes I buy fertilizer for hydroponics, but as long as it has micro-nutrients it really doesn't matter what ratio you use. I have used fertilizer for tomatoes, roses, palms, citrus, orchids, or any other acid loving plant. For Holiday cactus, use a diluted fertilizer at 1/4 the recommended strength and put it in a spray bottle. Spray it on your plant once a week. This concept is better known as weekly weakly. It works really well for almost every plant imaginable.

ewwmayo - the plant sensor just measures water, temperature and lighting conditions. As far as the fertilizer, it just lists the type of recommended fertilizer based on the plant, from its plant library. When placing the sensor in a plant, you tell it what kind of plant it is so it can analyze weather the water/temperature/lighting conditions are appropriate for that specific plant.

Renee - Best take the recommended fertilizers with a grain of salt. Many here would recommend Foliage Pro 9:3:6 or Miracle Gro 12:4:8 for most plants (which includes succulents/cacti).

Most important is to follow the bottle instructions for container plant concentrations.

If you are really enjoying the plant sensor so far, I would recommend getting a digital EC tester (online for cheap). I used mine to determine what concentration I should fertilize at and how often.

I really enjoy my plant sensors and have been heavily researching them and their use. Feel free to ask any questions anytime!

I approach fertilizing by first defining what I feel is the ideal set of conditions (for the plant) and setting it as the goal for getting appropriate nutrition to plants in containers. I think it would be difficult to argue with the precept
that our focus in supplying supplemental nutrition to our plants should be on
ensuring all the nutrients plants normally assimilate from the soil are A) IN
the soil and available for uptake at all times, B) in the soil in a favorable
ratio - that is to say in a ratio that mimics as closely as possible the ratio at which the plant
actually uses the nutrient, C) at a concentration high enough to ensure there are no
nutritional deficiencies, yet still low enough to ensure the plant's ability to
take up water, and the nutrients dissolved in that water won't be impeded (by a
high concentration of solubles in the soil solution).

In keeping with my belief that what defines our proficiency (as growers) is how well we eliminate those factors that limit our plants' ability to function efficiently, I simply eliminate practices that interfere with any one or more of A, B, or C; which leaves me decided that the easiest way, and perhaps the only way to achieve ABC above is to use a soluble fertilizer that provides nutrients in the ratio at which the plant uses them and to use a soil and watering habits that will work together to allow you to maintain the level of nutrients in the soil in that 'not too high/ not too low' range.

Al

Thanks ewwmayo - I'm going to stop on my way home tonight and grab one of your recommended fertilizers or something similar, for use on both plants, depending on what they have. And thanks so much for the information about the EC tester and your offer to help me out with any future questions regarding using sensors/testers/etc!

Al, I appreciate your advice as well. Unfortunately I am just a novice with a couple of houseplants so it may quite some time before I have the information, knowledge and resources I need to really evaluate ABC and described. Will certainly keep all that in mind though as I learn!

No problem. I was actually watching to see if you'd ask how to implement ABC, since it's so easy. Best luck to you.

Al

Well Renee,

If it's not too late you could even get what's called a balanced fertilizer. One w/ all the same #s, like 20-20-20 which can be used on most plants. Because I grow succulents, tropical cacti, Hoyas (epiphytes) & some other tropicals, I didn't want to have to buy different fertilizers. A balanced one as mentioned above can be regarded as all purpose, especially if you only have a couple of plants. I know some will disagree, but I share what I've experienced. I've used Miracle Grow (both powdered & liquid) Schultz, Peters, different things. Recently a plant friend allowed me to buy a bit of his Foliage Pro to try it myself, but that was last Spring so I haven't really had time enough to tell.

Personally I'd take the gizmos w/a grain of salt, the sensors too for that matter. I try to observe the plants closely & recommend you get used to the weight of the pots dry vs. watered, to help understand its needs, rather than relying on the meter.

Which ever way you go, enjoy & welcome to houseplants.

The idea that the exact NPK ratio is important is a big fat lie perpetrated by manufacturers to sell more fertilizer, i.e., they want you to buy a different fertilizer for every kind of plant that you have. In reality, whatever soluble nutrients the plants don't use will leach away, provided that you occasionally percolate the soil with water. More importantly, most fertilizers lack the macronutrients, calcium, magnesium, sulfur and sometimes silicon. If you look at the elemental analysis of most kinds of plant leaves, you will find that calcium and potassium contents are approximately equal. E.g., see

http://agbioresearch.msu.edu/uploads/files/Research_Center/NW_Mich_Hort/General/MSUFruitLeafAnalysisGuidelines.pdf

And, some kinds of monocots, e.g., rice, contain similarly large amounts of silicon. Most typically, potting mixes contain dolomitic lime that slowly supplies calcium and magnesium but that is inadequate when plants grow sufficiently fast or the supply becomes exhausted. There is a problem in that soluble forms of calcium are likely to form insoluble precipitates with soluble phosphates, sulfates and silicates which, if mixed prior to application of fertilizer, will prevent penetration of the soil. The simplest remedy to this problem is to separately apply soluble calcium and silicates from the other nutrients. Then, at least, the precipitates will form within the soil near the roots. Another important, often ignored, factor is that urea or urea phosphate have growth regulator properties that other sources of nitrogen do not have. The optimum amount of urea, which probably varies with the kind of plant, stimulates growth in ways that other forms of nitrogen can't, but, too much retards growth.

The least expensive method that I have found to do nearly optimum fertilization of potted plants is to alternately water with a solution of calcium nitrate and a hydroponic fertilizer combined with 10%-20% urea. Sometimes I experiment with potassium silicate. More specifically, I use these:

https://hydro-gardens.com/product/hobby-formula-5lbs-box-10-8-22x5/

(Except the formula has changed since I bought it. Before, it contained no urea).

https://hydro-gardens.com/product/calcium-nitrate-5lbs-box-cano3x5/

https://hydro-gardens.com/product/potassium-silicate-1gal-bottle-ksio2/

Apparently, hydro-gardens no longer sells urea but it is easy enough to buy on ebay:

http://www.ebay.com/sch/i.html?poi=&adpos=1t1&ul_noapp=true&geo_id=10232&MT_ID=71&crlp=98943217520_867&keyword=urea-&rlsatarget=kwd-123306347342&_nkw=urea-&device=c&crdt=0&treatment_id=7&clk_rvr_id=974092121395

Urea phosphate is preferable to urea because it improves the solubility of calcium, but, it is difficult to get in small quantities.

I think you have it quite wrong, and misread what I said. Fertilizer manufacturers have created market openings that needn't be. Let's use 'bloom booster fertilizers as an example'. No plant uses more P than N. When I pressed Dave Neal, CEO of Dyna-Grow on that issue because of what I considered to me misinformation disseminated by one of his employees, this is how he responded:

From Dave: "Al - You are correct. We market high P fertilizers because people "believe" [his emphasis] they need them. As you have noted, our Foliage-Pro does a great job start to finish. However, it is simpler to give the market what they think they need than to try to reeducate it [my emphasis]. There is some evidence to believe that low N helps to convince a plant to stop its vegetative growth and move into its reproductive phase (flowering), but environmental factors are probably more important. P is typically 5th or 6th in order of importance of the six macronutrients. There is little scientific justification for higher P formulas, but marketing does come into play for the vast majority of users who lack any real understanding of plant nutritional requirements. Therefore, the market is flooded with a plethora of snake oil products that provide little benefit and can actually do harm. For example, one exhibitor at a hydroponic trade show had a calcium supplement with 2% calcium derived from calcium chloride. Can you guess what continued application of 2% chloride would do to plants?'

I hope this answers your question and am sorry for XXX's (name deleted) inaccurate response.

Cordially,
Dave Neal, CEO
Dyna-Gro Nutrition Solutions ...."

It's illogical to infer from the fact that fertilizer manufacturers create these market openings that providing nutrients in the ratio at which the plant actually uses them isn't of value. What I set forth, and what the CEO of Dyna-Gro concurred with is, an extremely high % of plants use very close to 6X as much N as P and about 3/5 the amount of P as K. When the calculations are done for how much P and K are actually included verses how P and K are reported, you'll see that fertilizers with 3:1:2 ratios supply nutrients in almost exactly that ratio (3:1:2), making all fertilizers with that ratio a potentially appropriate source of those 3 macro-nutrients. Whether or not the fertilizer is actually appropriate for container culture depends on other factors what else it contains, in what form, in what ratio additional nutrients are supplied, and whether or not it allows the grower to easily supply nutrients the fertilizer might lack. E.g., most soluble fertilizers lack Ca, Mg, or both, and additionally often lack important secondary macros and or micros.

If you disagree with what I said, it leaves you burdened with redefining the goal I mentioned upthread,

I think it would be difficult to argue with the precept that our focus in supplying supplemental nutrition to our plants should be on ensuring all the nutrients plants normally assimilate from the soil are A) IN the soil and available for uptake at all times, B) in the soil in a favorable ratio - that is to say in a ratio that mimics as closely as possible the ratio at which the plant actually uses the nutrient, C) at a concentration high enough to ensure there are no nutritional deficiencies, yet still low enough to ensure the plant's ability to take up water, and the nutrients dissolved in that water won't be impeded (by a high concentration of solubles in the soil solution).

AND discussing how to attain that goal. I'm quite certain it would be slightly more advantageous to the plant if every nutrient was individually tailored to suit each individual (plant), but we also need to be realistic about the fact that's just not going to happen except in an extremely miniscule number of cases. So given that facility is also a factor, it's hard to argue against the fact that a singular source of nutrients would be nice.

Al

"I think you have it quite wrong, and misread what I said."

To whom are you speaking?

From Dave: "P is typically 5th or 6th in order of importance of the six macronutrients. There is little scientific justification for higher P formulas"

There is scientific evidence that plant roots have a strong tropism to grow in the direction of the phosphate gradient, i.e., phosphorus stimulates root growth without necessarily being absorbed by the plant. E.g., see

https://archive.org/stream/jstor-2465652/2465652_djvu.txt

That's probably why the old Miracle-Gro 15-30-15 was so successful before Peters changed it.

Dynagro, has a 0.4 Ca/K20 ratio = 0.48 Ca/K which is too low. As I said before, it should be approximately 1. Also, Dynagro could be improved for soil application by adding urea or urea phosphate.

" how much P and K are actually included verses how P and K are reported, you'll see that fertilizers with 3:1:2 ratios supply nutrients in almost exactly that ratio (3:1:2),"

The ratios stated on the box are not N-P-K but, instead, N - P2O5 - K2O. These numbers are fictitious in that there may be no P2O5 or K20. It may even be possible for the sum of the numbers to be greater than 100.

Guys, pls. be reminded that the OP said they had TWO plants.

This in-depth discussion you're sharing may matter to you both, but could be rather overwhelming to a newcomer w/ just a couple of plants.

Lena

You're misreading what I said AGAIN. The actual amounts of P and K in fertilizers is actually only 43% and 83% (respectively) of what's reported on packaging.

Dyna-Gro is a company - not a fertilizer.

I DO beg a pardon for my misstatement "how much P and K are actually included verses how P and K are reported, you'll see that fertilizers with 3:1:2 ratios supply nutrients in almost exactly that ratio (3:1:2)," My intent was to illustrate that a 3:1:2 ratio meshes well with the fact that the average plant uses about 6X as much N as P and 3/5 as much K as N. I had actually written "3:1:2 ratios supply nutrients in almost exactly that ratio (roughly) 10:1.5:6", but got distracted by the phone and changed what I'd written.It should be clear it was a misstatement and not an after the fact change of mind, given that I made a similar statement about actual usage and do understand how the .43/.83 factors play out.

Also, I'm not sure how chemotropism (in those plants that might be found to exhibit the response) would be a plus for plants in pots? Further, the study notes in its conclusion that, "The stronger solutions used (1.5 per cent.), cause first a curving toward the salt and then death". This hardly makes the case for supplying 5.2X the amount of P the plant can use, (as 15-30-15 does - viewed as a function of N); and if chemotropism ends in the death of plant organs because the plant has no avoidance mechanism, we should probably do all we can to ensure the plant isn't left to deal with a phytotoxic soil solution.

Since roots are opportunistic and only grow where conditions support growth, it really shouldn't be any more of a surprise that plants might be chemotropic than it would be to discover they are phototropic or geo/gravitropic.

I noticed you didn't offer what you thought the goal should be for fertilizing containerized plants, or how to best attain your vision of what the goal should be. I'll watch for that.

Al

"Since roots are opportunistic and only grow where conditions support growth"

No, as you quoted, "The stronger solutions used (1.5 per cent.), cause first a curving toward the salt and then death". In this case, the phytotoxic element was sodium, not phosphorus, therefore this is not evidence for avoiding high concentrations of phosphorus.

"Also, I'm not sure how chemotropism (in those plants that might be found to exhibit the response) would be a plus for plants in pots?"

I have never used or recommended 15-30-15 for potted plants, but, I like it for transplanting tomato seedlings outdoors. You initiated the more general conversation by quoting Dave Neal and I replied to that. Previous to that, I did not read your posts and was responding to the OP.

"I noticed you didn't offer what you thought the goal should be for fertilizing containerized plants, or how to best attain your vision of what the goal should be."

For house and ornamental greenhouse plants, my goal is to grow specimen plants as fast and cheaply as possible, or, at least, beat my personal records. I enjoy watching plants grow fast enough so that I can see a change every couple of hours. I tend to aesthetically prefer big leaves, preferably variegated.

So chemotropism can't be viewed as a positive (makes me really unsure about why it was brought up).

You don't really have a supplementation plan you can define - or don't disagree with/can't improve on what I said as an appropriate goal. I was hoping you would share what your idea of nutritional utopia would be and share a plan about how to get there.

You offer "That's probably why the old Miracle-Gro 15-30-15 was so successful before Peters changed it", but you don't recommend it and only use it for tomato seedlings.

I think I have it, but why are we having this conversation, again? Oh yeah - it's that thing about precise NPK ratios not being important. Would that mean that 10-52-10, or 0-10-10 is as appropriate as 12-4-8 for plants in containers?

Al

"So chemotropism can't be viewed as a positive (makes me really unsure about why it was brought up)."

No, on average, in some meaningful statistical sense, all tropisms are a positive. Unusual exceptions do not define the rule. For example, a leaf on one of my houseplants was attracted via phototropism to a light bulb until it touched the bulb and became burned. It would be wrong to conclude from that that phototropism can't be viewed as a positive.

"You don't really have a supplementation plan you can define - or don't disagree with/can't improve on what I said as an appropriate goal."

1. I added economic constraints, i.e., "least expensive," that you didn't.

2. I added ergonomic constraints, i.e., "simplest remedy to this problem," that you didn't.

3. I discussed the importance of urea or urea phosphate, that you didn't.

4. I discussed occasionally percolating the pots with water to flush out excess solutes, that you didn't.

"precise NPK ratios not being important. Would that mean that 10-52-10, or 0-10-10 is as appropriate as 12-4-8 for plants in containers?"

For "0-10-10," obviously not. It is so obvious that you shouldn't even ask. If 10-52-10 was free, as, for example, already on hand, and 12-4-8 cost $1/lb., all else equal, I would recommend using the 10-52-10 until the free supply was exhausted before buying 12-4-8.

Actually, I don't like urea for houseplants/ most plants because it promotes coarse growth (large leaves and long internodes (FP 9-3-6 is urea-free). Using toxic levels of P (in 10-52-10) that cause myriad issues (high pH, antagonistic deficiencies, unnecessarily high EC/TDS levels, ......) just because it might be free is a really poor idea.

I've always been an extremely strong proponent of flushing the soil regularly - have mentioned it literally thousands of times - just not here because the conversation with the OP hadn't progressed that far..

I stated a very clear goal that leaves the grower in complete control over his/her nutritional supplementation program and can be achieved using 1 soluble fertilizer. You criticized it, but can't improve on it or even describe how to go about implementing any program. A good place for me to cut short the meaningless back & forth.

Al

"Actually, I don't like urea for houseplants/ most plants because it promotes coarse growth (large leaves and long internodes (FP 9-3-6 is urea-free). "

It seems like you are describing the effects of gibberellic acid instead of urea. In my experience, urea makes the stems of tomato seedlings proportionately thicker and therefore less likely to fold over without staking. And, I have never noticed urea cause anything that resembles etiolation on a plant.

Speak of the Devil, here is a Dynagro user who is worried about a proportionately thin lower stem on a pepper plant:

http://forums.gardenweb.com/discussions/3622052/strange-pepper-growth?n=1

"whatever"

These are photos of tomato seedlings, 22 days after germination, fertilized with a solution of the old, no longer available, Hydro-Gardens 10-8-22, 5 grams/gallon plus urea phosphate, 1 gram/gallon:

http://www.general-cathexis.com/images/BigZac3.6.jpg
http://www.general-cathexis.com/images/BestBoy3.6.jpg
http://www.general-cathexis.com/images/VelvetRed3.6.jpg

Left to right, grown under daylight, Gro-Lux fluorescent, Gro-Lux Plus Incandescent. Top to bottom, the varieties were Big Zac, Best Boy, and Velvet Red. For size comparison, the diameter of the of the pot tops is 4".

This is a partial analysis of the old Hydro-Gardens 10-8-22:

Ca 5%
Mg 1%
S 2%
B 0.05%
Cu 0.05%
Fe 0.2%
Mn 0.1%
Mo 0.05%
Zn 0.05%

Nitrate N 8%
Ammonia N 2%

I defy anyone to produce larger and stockier tomato plants within 22 days of germination without using urea or urea phosphate.

Jumping from topic to topic and offering statements that invite correction makes me think what you're doing is intentional, so this will be a good place to exit the conversation. But first, urea is an organic chemical compound, created synthetically from ammonia and CO2 by dehydrating ammonium carbamate under high heat and pressure. It's not a growth regulator (hormone) and doesn't act as a growth regulator, even though like all forms of N it affects the growth habit of a plant by causing coarse growth - larger leaves and longer internodes. Too much Urea doesn't reverse the trend and has roughly the same effects on EC/TDS and water's ability to cross semi-permeable membranes as excesses of other forms of N. Suggesting that I'm confusing the effects of urea with those of gibberellins is like suggesting I'm confusing uses of a truck tire with a dinner fork. I'm not confused, but I'm having difficulty understanding the reasoning. If one uses a broom to strike a baseball, the act doesn't transform it into a bat.

Etiolation is a symptomatic manifestation that occurs in plants due to lack of light. It's conspicuously characterized by a dearth of chlorophyll, long internodes, weak roots, and leaves that don't fully form or open completely, as well as myriad other physiological and physical symptoms. Because large amounts of any form of N or use of urea can produce some of the same symptoms as etiolation, levels of N at luxury levels and beyond (and particularly urea) might SEEM to increase the plant's symptomatic response to the lack of light, but it doesn't cause etiolation.

Al

He/she is ABSOLUTELY intentionally trying to stir the pot, Al. It's best to just ignore it. I bumped a thread about NPK over on the hot pepper side that had some great info in it that you provided. Turned out to be a sh-t show all afternoon. I deleted all my posts; it was a waste of time. Apparently, he/she believes that anyone who listens to any advice you give is part of your "cult," and that you "pontificate" yourself with all of your "verbosity." The guy/gal's a troll. Just ignore it. Sorry to drag this topic over to this forum, just be aware. My $0.02. Happy growing, everyone.

Thanks - I'd already decided the intent was to produce heat rather than light - reason enough to move along. Appreciate the heads-up.

Al

"But first, urea is an organic chemical compound, created synthetically from ammonia and CO2 by dehydrating ammonium carbamate under high heat and pressure."

True but irrelevant. Your habit of pontificating on irrelevant facts shows that you do not know what is relevant.

"It's not a growth regulator (hormone) and doesn't act as a growth regulator"

"Growth regulator" and "hormone" are not synonyms. All plant hormones are growth regulators but not vice versa. As far as I know, I am the only one to call urea a growth regulator and this is based on my own experience. But, if you review the literature, you will find many examples of urea having a very different effect than ammonium or nitrate forms for nitrogen, especially when applied as a foliar spray. Also, it is well know and easily verified that urea inhibits the germination of seeds. And, I have heard a rumor, that I can't verify, that a foliar spray of urea forces leaf stomata to open.

However, a chemically similar compound, thiourea, has been called a "growth regulator" many times in the literature. If you Google;

"plant growth regulator" thiourea

, you will get 41,800 results, some that are relevant.

"like all forms of N it affects the growth habit of a plant by causing coarse growth - larger leaves and longer internodes."

Without changing shape, a larger plant has longer internodes. It is well know that N fertilizers makes plants larger. Shape is the issue. I provided evidence that urea can produce thick stems relative to height in tomato plants, a desirable trait because it requires less staking. You provided no evidence that this isn't true.

See, Al? ;)

I compared the price of Dyna-Gro 9-3-6 (a liquid) with some solid fertilizers. Long story short, Dyna-Gro does not give much of a price break for larger amounts, but, the price for small amounts is reasonable. To do a price comparison, you need to know the density of the liquid, which is 1.43 g./ml or 11.92 lbs./gal.. From

http://www.greenhousemegastore.com/product/dyna-gro-foliage-pro-9-3-6/s

the price of Dyna-Gro 9-3-6 is $3.52/lb. and $3.33/lb. for 1 gallon and 5 gallon amounts, respectively.

For Chem-Gro 10-8-22, the price is $4.19/lb. and $1.64/lb. for 5 lb. and 25 lb. amounts, respectively.

For Peters Excel 15-5-15 Cal-Mag Fertilizer, the price of 25 lbs. is $42.75 or $1.71/lb. at

http://www.growersupply.com/peex15calmag.html

Incidentally, all of the phosphorus in Excel 15-5-15 is in the form of urea phosphate.