It's ok, but you don't really need 'high' nitrogen fertilizer, just a fairly well balanced one for house plants.

Soluble fertilizers like Miracle-Gro, Peters, and many others use urea as their N source and are widely used by bonsai enthusiasts. I am quite happy using Dyna-Gro's Foliage-Pro 9-3-6 because it has all 12 essential nutrients in as close to the same NPK RATIO that plants use, and all the nutrients are present in a favorable ratio to each other. This is important from the perspective that it allows you to fertilize at the lowest rate possible and still not have nutritional deficiencies. By happenstance, the FP 9-3-6 is also urea-free.

I may be getting deeper into fertilizing that you wish, so I'll offer a couple of additional thoughts & you can let me know if you want me to expand.

Houseplant fertilizers are generally not a good choice for bonsai, for the reason I listed above. Most houseplant fertilizers have NPK %s like 5-10-5 or 10-15-10. The middle number is P(hosphorous) and it is usually the largest % of the whole. Plants actually use about 6X more N than P, so when you supply all that extra P in 5-10-5 it's almost 6X MORE than needed as it relates to N - after factoring for the fact that P is ACTUALLY reported as P2O5 and is ACTUALLY only 43% of the REPORTED %. What this means is you are unnecessarily contributing to the TDS/EC (roughly, the salt level) of the soil, which makes it harder for plants to take up water and the nutrients dissolved in that water. The extra P also contributes to a usually unwanted increase in pH and makes it more difficult for the plant to take up several other nutrients, mainly Fe (iron) and Mn (manganese).

Many choose 1:1:1 ratio fertilizers like 20-20-20 because they say they prefer not to supply all the "extra N" that you find in 3:1:2 ratio fertilizers like 24-8-16, 12-4-8, 9-3-6 ....., but then they turn around and fertilize the plant to fill the plant's N needs. The end result is they end up supplying the same amount of N, but because the 1:1:1 ratio fertilizers supply more K and much more P than the plant requires (again, as a function of N usage) all they are doing is supplying nutrients the plant can't/won't use ..... just to get enough N. Liebig's Law of the Minimum recognizes excesses of factors with the potential to limit plant growth potentially as limiting as deficiencies.
I would sum up this thought by saying you don't/can't limit the plant's N supply by changing NPK %, you limit it by limiting the actual dosage of N; or, it's dot the fertilizer that limits N supply, it's the grower.

Al

Al -

Resurrecting this post. I appreciate your explanation, but this raises the question - why do companies sell fertilizers with a high P ratio? Your post makes me wonder if I should chuck my Dyna Gro Bonzai Pro. To be honest, I was planning to use it for my container citrus, since I wanted to encourage fruit production instead of leaf growth.

Thank you for your thoughts!

Some plants/trees must need it, and/or their location/zone makes it desirable. S'cuse me, I'm not Al, just taking a guess at things.

This is a copy of an email that came from Dave Neal at Dyna-Gro. A GW member had called Dyna-Gro and asked what fertilizer to use on her blooming plant. The woman she talked to suggested a high-P "blooming" formula. I wrote Dave directly and pressed him on the issue. Here is the response:

You are correct. We market a high P (Liquid Bloom) "believe" they need this. 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. 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 Zina's inaccurate response.
Cordially,
Dave Neal, CEO
Dyna-Gro Nutrition Solutions
2775 Giant Rd.
Richmond, CA 94806color>

Essentially, someone created a market for high-P formulations because of the MYTH that P is "for roots and blooms". The rest of the industry, not wanting to use market share, followed suit, each with their own unsupportable claims and promises of benefits the fertilizer can't deliver. The unsuspecting public buys into the claims every time they purchase the product, thus perpetuating the myth.

Even 1:1:1 ratio fertilizers like 20-20-20, are high-P fertilizers in that they supply about 2.6X as much P as the plant can use in relation to N.

Al

Very interesting and enlightening!

hello

that would be for growing season only? Or it also applies to fall? What about winter for tropical/subtropical trees?

What is meant by "that"? What part of what was said are you referring to, Matt?

To use 3-1-2 with low P.

meaning should i use 3-1-2 all year round or adapt depending of the season?

Nutritional needs change somewhat as the phases of the growth cycle come and go, but in order to adjust for that, you would need to be willing to learn the plant's precise needs ..... and no one removes nutrients from soil in the landscape when winter comes.

I do adjust the ratio of nutrients supplied for a few plants like tomato and hibiscus, but I still have 9-3-6 running in the background. For instance, I get best tomato results when I feed at luxury levels of 9-3-6 mixed with some 10-52-10 until about this time of year, then, I still use the 9-3-6, but I add a little potash for the K. For hibiscus, I still use 9-3-6, but I add an equal measure of potash to the solution to satisfy their K craving. For all other plants, it's nothing but 9-3-6 and ProTeKt, all year long.

If you have indoor plants, you'll need to pull back on the rate during winter (if not growing under lights and/or if temps are below 65*F. I do grow under lights in very fast media, so I fertilize with 1/4 tsp/gal at every watering. I fertilize weekly when mean temps are below 80*F in summer and plants are outdoors and use 1.5 tsp/gallon.

Al