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To Fertilize or Not To Fertilize? Help?

Posted by uniquelydivine 6 (My Page) on
Sun, Dec 2, 12 at 17:43

Hi Everyone!

I need some advice as far as fertilizing. I have some plants that I fertilize every time I water and I just wanted to know if its a good idea or not.

They are:

African Violet

I just need to make sure it is fine to fertilize them all year round, every time I water. The soil they were potted in did not have any fertilizer. I use a very low solution (1/4 teaspoon per gallon). The formula is 7-9-5 and contains no urea. These plants only get water once a week (they Zebra may get more and pothos can go up to two weeks without water).

Is it a problem fertilizing every time I water?


Follow-Up Postings:

RE: To Fertilize or Not To Fertilize? Help?

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Sun, Dec 2, 12 at 21:43

I fertilize in winter every time I water because it can be very effective if your soil choice and watering habits allow. IF your soil allows you to water copiously, so you're flushing the soil each time you water, and you adhere to that practice, it's pretty foolproof, though I think the 7-9-5 has much more P than your plant wants or can use. If you're using a soil that makes you hesitate to saturate the soil fully and beyond, so at least 10-20% of the total volume of water applied exits the drain, I think you need another plan.


RE: To Fertilize or Not To Fertilize? Help?

Tapla, if I make sure the water comes through the bottom then everything should be ok? The soil drains soon as I water the excess comes through almost immediately and I discard the excess right away. Should I flush the soil sometimes? Also, I noticed some yellowing on the tips of my anthurium's leaves. What can be a cause of that problem? Thanks!

RE: To Fertilize or Not To Fertilize? Help?

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Mon, Dec 3, 12 at 21:36

Lots of things can cause burned leaf tips and margins, but the main issues are usually poor root function due to a soil that remains saturated for extended periods, or a build-up of salts in the soil due to poor watering practices, usually made necessity by a soil too water retentive. Factors that frequently contribute to the problem are low humidity or the presence of an element in the soil that the plant is extra sensitive to.

All the plants I over-winter indoors are in the gritty mix. When I water/fertilize use just under 1/4 tsp of Foliage-Pro 9-3-6 per gallon of water, and I make sure I water until after water is appearing at the drain. I estimate that 10-20% of the water I apply flushes through the pot, so the level of salts never increases to levels that can damage the plant.

The 7-9-5 is about 17% more concentrated than the 9-3-6, so I think I'd cut back a little on the dosage if I were you. There are 24 drops in 1/4 tsp, so I'd maybe use an eye dropper and cut that back to about 18 drops/gallon.


RE: To Fertilize or Not To Fertilize? Help?

Thanks Tapla (Al)! You're amazing! Do you have a book? You should really write one because you're great! I'm going to get a dropper and use less of the fertilizer per gallon and see what happens. The soil is fast draining but I find it doesn't dry out "fast." I water the anthurium weekly. I will probably wait a little longer and see if that helps as well. My problem is that I think plants can't go longer without getting water and I may be incorrect.

I got another question for you: I've had my Peace Lily for about 8 months now. It bloomed from when I got it (April) to about late August/early September. No blooms since then. Any advice on what I can do to encourage blooms or is it just resting? The tips of the leaves are brown and some leaves have brown spots on them. Do you know what causes that? Even though I've only had the plant for 8 months, roots are starting to come out in the bottom. Should I repot this time of year? I have it at work and its under artificial light. It doesn't get natural light but it is directly under the artificial one. And I don't give it any fertilizer. Should I?

RE: To Fertilize or Not To Fertilize? Help?

Maybe the 7-9-5 might not be the ideal npk ratio. Maybe it may not be BEST for indoor plants that live years. The thing is I watched a chili harvest that was amazing from someone that used the dyna gro 7-9-5.

RE: To Fertilize or Not To Fertilize? Help?

So if the 7-9-5 isn't a good idea what is then? I'm using the Dynamic Gro "Grow" formula. It was recommended by someone that's had indoor plants for decades.

I even contacted Dyna Gro and they recommended the "Grow" formula over the others.

RE: To Fertilize or Not To Fertilize? Help?

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Tue, Dec 4, 12 at 14:25

PLs are being hybridized to extent their blooming period. My experience is that if cultural conditions are favorable, you'll get SOME blooming outside the summer period when you should expect the most profusion. It's likely that if you acquired your plant in Apr and it was blooming well, there was probably some specialized manipulation that involved chemicals (hormones), and/or light/temperature manipulation. I've noticed the most blooms between Jun - Aug on all the plants I've grown.

ALL plants can benefit from having enough fertilizer in the soil at all times to prevent deficiencies, but not so much that it makes it difficult for the plant to take up water and nutrients. Those that suggest that fertilizer should be withheld in winter while growth is slow, are ignoring the fact that it's not fertilizer in ADEQUATE amounts that should be avoided, it's fertilizer in excessive amounts that makes trouble, Usually, the advice to NOT fertilize is offered by growers who are attempting to deal with the salt build-up that occurs in heavy soils because they can't water properly w/o risking root problems. It makes absolutely no sense to deprive plants of nutrition in the winter because growth is slow, but it DOES make good sense to take steps necessary to prevent a build-up of salts. This can easily be accomplished without withholding fertilizers in a way that's much healthier for the plant - which is the method we are discussing now.

I'm not sure who you talked to at Dyna-Gro, but in phone & email conversations I've had with Dave Neal, the CEO, he was always quick to agree that 9-3-6 was always their 'go to' fertilizer.

From Dave: "You are correct. We market high P fertilizers because people "believe" 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 my emphasis] 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 (Xxxx's) inaccurate response.

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

It's not that you can't grow healthy plants using 7-9-5, but plants use about 6X as much P ass N, so all that extra P has only the potential to limit. An excess of any single element can be as limiting as a deficiency.


RE: To Fertilize or Not To Fertilize? Help?

I don't know what happened but I can't find the original response. I sent them another email yesterday and she gave me a generic response. The one from the first person was more detailed. I'm mad I can't find it. Here is today's response:

Our Grow 7-9-5 is an all purpose formula, which is good for promoting healthy flowers and leaves. The Foliage-Pro 9-3-6 will promote leaves. If you are having problems with blooming our Bloom 3-12-6 will push plants into the bloom stage and produce large, vibrant blooms.
Susan Sommer, G.M.
Dyna-Gro Nutrition Solution

RE: To Fertilize or Not To Fertilize? Help?

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Wed, Dec 5, 12 at 14:23

What you received in reply is boiler plate - sorry. If you ask her, or better yet, Dave, "What would be the purpose/point of providing almost 10x as much P than the plant can/will use in your 3-6-12, and almost 3.5x as much in the 7-9-5", I bet you'll get an entirely different answer - probably based on their not wanting to forgo filling a market niche. See Dave's email above.

Just below is something I wrote about high-P fertilizers. It should help to explain why anyone would be hard-pressed to come up with even an imaginary situation where a high-P fertilizer (one where the middle number [P] is larger than the first number [N]. Even 1:1:1 ratio fertilizers, like 20-20-20 or 14-14-14 have more P than the plant can/will use in relation to the amount of N supplied by about 2.3x.

How Much P is Enough?

Let's first look at the role of fertilizers in general. There are 6 factors that affect plant growth and yield; they are: air, water, light, temperature, soil or media, and nutrients. Liebig's Law of Limiting Factors states the most deficient factor limits plant growth and increasing the supply of non-limiting factors will not increase plant growth. Only by increasing most deficient factor will the plant growth increase. There is also an optimum combination of the factors and increasing them, individually or in various combinations, can lead to toxicity for the plant.

From the above, we can say that when any nutritional element is deficient in the soil, plant growth slows. We have a term for this occurrence: environmental dormancy. When the deficient element is restored to adequacy levels the environmental constraint caused by the deficient element is eliminated and plant growth can resumes at a normal rate, as long as there are not additional limiting factors. Continuing to increase the element beyond the adequacy range offers no benefits and can deleteriously affect the plant - often in several ways, depending on the element.

Somewhere along the way, we curiously began to look at fertilizers as miraculous assemblages of growth drugs, and started interpreting the restorative (of normal growth) effect of fertilizer as stimulation beyond what a normal growth rate would be if all nutrients were adequately present in soils. It's no small wonder that we come away with the idea that there are 'miracle concoctions' out there and often end up placing more hope than is reasonable in them. In couplet with the hope for the 'miracle tonic' is 'more must be better'. I'll use that idea as the lead-in to my thoughts on high phosphorous fertilizer blends.

Among container growers you often find common belief that high phosphorus (P) content fertilizers are a requirement for promotion of root growth and/or flowering. Fertilizer blends like 15-30-15, and even 10-52-10 are sold under names that imply that you actually NEED these formulas for plants to bloom well and to produce strong roots. Lets examine that idea in a little more depth.
While anecdotal evidence abounds, there is very little scientific evidence to show any need for such products. I've mentioned in other posts that high-P fertilizers are a historical carry-over from when it was most common for plants to be started in outdoor soil beds, the soil in which was usually still quite cold at sowing time. Both the solubility of P and plants' ability to take it up are reduced in cold soils, so it was reasoned that fertilizing with high levels of P insured that at least some would be available during periods of growth in chilled soils.

We know that tissue analysis of leaves, roots, flowers - any of the live tissues of healthy plants will reveal that P is present in tissues at an average of 1/6 that of nitrogen (N) and about 1/4 that of potassium (K). Many plants even contain as much calcium (Ca) as P. If we know that we cannot expect P to be found in higher concentrations in the roots and blooms than we find in foliage, how can we justify the belief that massive doses of P are important to their formation?

It is well known among experienced growers that withholding N when all other nutrients are available at adequate levels induces bloom production on smaller and younger plants. Even though plants USE nutrients at approximately a 3:.5:2 ratio (note that N is 6 times the level of P, and K is 4 times the level of P), most greenhouse operations purposely fertilize with something very near a 2:1:2 ratio to limit vegetative growth so they can sell a compact plant sporting pretty blooms to tempt you.

Simply limiting N limits vegetative growth, but it does nothing to limit photosynthesis. The plant keeps making food, but it cannot use it to grow leaves and extend stems because of the lack of N. To where should we imagine the energy goes? It goes into producing blooms and fruit.

What harm might there be in a little extra P in our soils? First consider that the popular 10-52-10 has almost 32 times more P than a huge percentage of plants could ever use. Even 1:1:1 fertilizer formulas like the popular 20-20-20 are already high P formulas because they have 6.25 times more P (in relation to N) than plants require to grow robustly and normally.

Evidence of phosphate overfertilizing usually always includes some degree of leaf chlorosis. P competes with iron (Fe) and manganese (Mn) ions for attachment sites and causes antagonistic deficiencies of these micronutrients. Unfortunately, the deficiency of these elements causes interveinal chlorosis (yellowing), and the first thing we normally consider as a fix for yellow leaves is more fertilizer, so we give the plants a good dose of our favorite bloom-bomb which causes, no surprise - worsening of the condition.

I'll close with an anecdote of how I used to fertilize plants with showy blooms before I had a better understanding of the overall picture. I would fertilize with a "bloom-boosting" fertilizer as long as foliage was bright green. As foliage inevitably yellowed, I would then switch to a high N formula until the color returned & start the cycle over again. I THOUGHT that the P was helping with the blooms and the yellowing was caused by a lack of N, which I quickly jumped to correct at the first evidence of yellow. I now understand that the high levels of P were what were causing the yellowing and it wasn't my returning to a high N formula that greened the plant up again, it was the reduction in the level of P in the soil when I stopped using the high-P formulation.


RE: To Fertilize or Not To Fertilize? Help?

If the water with added fertilizer splashes onto the leaves at all when your watering, might be causing the the leaves to burn. Some plants burn very easily when this happens and some don't at all. If that is the cause of the browning, then adding the fertilizer to the soil first, and then adding the water to dilute it into the soil, will generally prevent this from happening. If you are confidant that your not getting fertilizer on the leaves when you water, then its probably either not enough sun, direct sun, over watering, under watering, or mineral buildup. Fertilizing in the winter is fine so long as water drains out of the pot each time you water it. other wise the fertilizer can build up in the soil to toxic levels. Also make sure that the water in the collection tray is discarded so that the base of the pot doesn't sit in that water, or make sure that the pot is raised up so that it doesn't sit directly in the water that runs off into the collection tray. If you think the plant is getting the right sun light, then flushing the soil out isn't a bad idea. It can flush out any buildup of minerals that may be causing the browning, or if its getting over watered, flushing out the soil can improve the drainage of your soil as the finer silt particles in the soil are flushed out.

RE: To Fertilize or Not To Fertilize? Help?

I'm going to contact Dave but I think I'm going to flush the soil of the Anthurium because I don't want it to get worse. Once I hear back from Dave, I will post his response. I started using the Dyna Gro in June so I'm thinking that light may be the reason why the leaves are yellowing. I did push the plant further away from the window just to be on the safe side.

Will post Dave's response....

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