Higher temperatures and fertilizer burn.

[davidwood]

Well I have had a bit of a disaster this week and it might serve as a warning to others, I have lost about 20% of all my leaves on some cv’s and what leaves left have all got serious fertilizer burn, I had heard the warnings but as I had lovely green healthy bushes I took no notice thinking mine where ok, it never occured to me that higher temperatures would have an affect on the fertilizer.

I fertilize my CV’s quite heavily and have done for months, a minimum of half a teaspoon of Booster and half a teaspoon of Fert with every gallon of water, I have been getting great results and me and the plants where very happy, so I ask myself what happened? And the only real change is the sudden rise in temperature and stronger sun, its gone from 80f to a 100f in the space of a couple of weeks and left my cv’s in a bit of a mess, still you live and learn and I shall be cutting right back, just Supernova for a couple of weeks and then half strength fertilizer from now on, or at least till October when the temperature drops.

[farmer d]

David I'm sorry to hear about the fert damage.  It's really tough to see your plants not at their peak after so much time. I know you'll get them back to that zone soon.

I'm really glad you posted this thread as it is a really important reminder to any of us who heavily feed our plants what will happen when it gets really hot.  They go into feeding overdrive and can really surprise us with how quickly things can change.  Like last year I will be watching the weather forecast very closely and cut back before the heat hits.

I was very fortunate last summer as we only had two times the temps stayed over 90F (32C) for an extended period of time so this was not an issue.  I get a premonition that will not be the case this summer.

For me the high heat is a stress much like the cold where I will want to spray more Supernova than usual and probably late in the day so it won't evaporate too quickly and get soaked up.

Farmer D

[helixturnhelix]

Sorry to hear this David.  That is part of the problem with feeding heavily during hot weather, the water demand is much increased due to evapotranspiration.  This means that the water demand has increased, but the nutrient demand has not.  So in trying to get more water, your plants are taking in more fertilizer as a consequence.  So they arent going into feeding overdrive as Darren has stated, but rather are absorbing more fertilizer as a consequence to trying to get more water. 

Darren, supernova does not evaporate but the water in the product does.  The product itself stays on the leaves because those molecules are too heavy to vaporize and stay as a residue.  With such heavy application, coupled with dry weather, there will likely be bio-accumulation of this product which may have negative consequences.     

What was presented in your interview on the HVH newsletter is the exact opposite of what you want to do during hot weather. 

"For the spring-through-fall growing season, for my bigger plants, 3-4 times a week, I used a hand-held 2-gallon watering can mixed with:

    2 heaping tablespoons of HVH Special-Blend fertilizer
    2 heaping tablespoons of HVH Booster
    2 capfuls of Super Nova Growth Enhancer

For my smaller plants I used:

    1 flat tablespoon each Special-Blend Fertilizer and Booster
    2 capfuls of Super Nova

I did see some minor leaf burn at this level, so it is the max I would do for now. As the hibiscus get bigger and more mature, I might either be able to give them more, or a maybe lot less if I see them so big and strong that they are doing great without much feeding, which is my hope. The resulting summer and fall growth was amazing.

In winter I feed once a month at most, in the same manner, but I only use:

    1 flat tablespoon of Special-Blend
    No Booster
    2 capfuls of Super Nova"

Rather than feed more during hot weather, you should feed the same or less and dilute it out.  During weather when the daily temp is 90 degrees or higher you should calculate the sum of fertilizer you are using and correct for the increased volume of water you are using.  This results in a decrease in concentration per watering, with the total nutrient application staying consistent for the week. 

There is still the problem that the vast majority of the fertilizer you are using at these concentrations not being used by the plants themselves.  In the case of nitrogen, it is promoting the growth of nitrifying bacteria in the soil.  These bacteria are transforming the engergetic state of the nitrogen in the fertilizer to one that is harder for the plant to absorb (conversion of ammonia to nitrate, which is less energetically favorable).  In the case of phosphorous, the excess is likely attaching to negatively charged particulates in the soil and is being washed down the drain.  Promoting gross over-fertilization of any garden or plant, increases nutrient concentrations in runoff leading to eutrophication, dead zones and toxic algal blooms. (Yes this may be one garden, but the sum of many gardens fertilizing this way is significant) 

I think what needs to be portrayed to readers is to optimize their fertilizing regimes to minimize waste, while not compromising growth and flowering.  Stating information like: "So with that in mind, and the fact that all my plants are planted in the ground with unlimited soil dimensions, I figured this would allow me to heavily feed without it being too risky to my plants. I figured I could really push their growth limits and could possibly figure out the feeding limits at the first signs of leaf burn." is a step in the wrong direction.  Fertilizing as much as it takes until it is harmful to the plant is not a philosophy that should be promoted.

Quotes taken from:
http://www.hiddenvalleyhibiscus.com/newsletters/february2012.htm
 

[davidwood]

Thanks Cris, I am actually gutted as to whats happened, I pride myself on my leaves and bushes more than the actual blooms, here in the tropics to have a nice healthy bush I concider an achievement in itself and I have allways had a theory that I look after the leaves and the general health of the plant and the blooms will look after themselves.

What I have planned to do and I think fits in with your advice on diluting is to not only lower the fert during the hot weather I will also feed every other day, one day just water, hopefully that will sort it all out.

[farmer d]

Chris I greatly appreciate your vast scientific knowledge and find it very useful in continually refining my overall plant care regime.  

Please keep in mind that the newsletter interview asked what I have been doing and my thinking behind it.  Anyone reading it can take from it whatever pieces they want and do their own further investigating as to what they think might be best for their microenvironment.  The more information at our disposal the better - and I am one who definitely is not content with just all the scientific parameters.  Maybe you can better explain how the conditions in laboratories and field studies that produce these standards perfectly mimics my garden's.  I use it as a guide and then go from there and I would guess there are some others who do so as well.

Everyone's setup is so unique that no one approach or set of scientific standards is going to be the right fit.  I take a lot of the scientific standards that you have stated over time along with a lot of other things that I hear and read as well and make my own judgement as to what I would like to try.  If I stick within all these scientific guidelines I feel that maybe I might miss out on something extraordinary and unexpected.  It's my call to make and I can share that without having to be judged for it.  Hey if my results or others don't coincide perfectly with the science then I am one to start looking for the wiggle room and further possibilities.  My hope is that we can show others a good example of how you can combine our two differing approaches and keep moving out the outer edge of what can be accomplished.

Yes you are far more knowledgable in the science of plant growing but that  doesn't mean that I am leading people astray when articulating what I observe and how I approach it.  We all know what the standard for outdoor winter growth and blooms before this year was for outdoors in a non-tropical climate so I am really glad that I didn't just say "ok" that is how it is.  I push the envelope and if I got some minor leaf burn on my plants in the process I think that is worth it to eventually figure more things out and get some extraordinary results.  

And for the record I never said to feed more during hot weather.  I go by the growing season and with the very even mild temperatures we had here during last spring/summer I didn't have to lower my feeding levels except a couple of times due to the weather.  Actually it was because of you that I was made aware ahead of time to decrease the feedings before a hot stretch of weather hit to avoid fert burn though that never materialized last year - so again thank you.  In my mind it does make sense to spray more often however when it starts getting really hot as that is just as much a stress for plants too.

My thinking is that as my plants get bigger and more mature I will probably be able to feed them a lot less as they will have what it takes to get through winter without any issues  - but that still remains to be seen.  I do question your concern with the overuse of fertilizer as I stated in the newsletter I really spread out the fertilizer across the entire planter as I have seen how far the root systems have grown and if anything I just soak the top layer of the soil thoroughly.  The results that David and I have seen are impressive enough for me to keep at it.

As for the fert burn I actually came down a tad from my first few attempts at the heavier fertilizing and what I quoted in the newsletter is the max amount I can do without any further burn which I haven't had since mid summer so I apologize if I didn't better explain that.  The burn I saw was on my smaller plants and even at a higher amount than stated in the newsletter still seemed to be ok with the big ones.

The nitrogen factor does concern me when combining both the SB & booster so I am working on a no nitrogen booster to better balance it out.  

[davidwood]

I agree with all you say there Darren, you pushing these boundaries and showing what is possible has improved my garden so much, my problem is through a lack of knowledge of hot weather and fertilization I pushed to hard and have suffered, still like I said you live and learn.

I was only thinking the other day that apart from your C of F and your Valentines Day your cv's in the ground aren't any bigger than my cv's in pots, yet you have 10 or 20 times more buds, now if we are both near the max on fertilizing the answer has to be your very heavy use of Supernova whats making that happen, like i say just a thought.

[Charlie]

David, it's entirely possible that the loss of leaves has nothing to do with fertilizing. Your use of fertilizer is moderate to low, not high. Can you describe the symptoms the leaves showed before they fell off the plant? Also, did you spray the leaves with anything else during the couple of weeks before they fell off? Did you increase the water as the temperatures increased or did the plants become drier than normal during that time? I don't think you have the solution yet because the problem is not really diagnosed fully.

Charlie

[helixturnhelix]

Some pics would be great David!

[davidwood]

David, it's entirely possible that the loss of leaves has nothing to do with fertilizing. Your use of fertilizer is moderate to low, not high. Can you describe the symptoms the leaves showed before they fell off the plant? Also, did you spray the leaves with anything else during the couple of weeks before they fell off? Did you increase the water as the temperatures increased or did the plants become drier than normal during that time? I don't think you have the solution yet because the problem is not really diagnosed fully.

Charlie

Charles I pulled some leaves out the bin for the photo, none actually fell off I trimmed them off.
I have done nothing different than my normal but like I say there was a very sharp rise in the temperature, coinciding with this rise was the sudden yellowing of 20 to 30% of my leaves [they did pretty much all appear at once and now seems to have calmed down], and also a lot of burning on the edges of some [not all]cv's.
As for watering I did not increase by much, the thing is I am pretty much on the max now and an increase would leave the soil permanently soggy, perhaps I need to water twice a day.

In the photo the yellow is a lot duller, its a very bright yellow in real life.

[davidwood]

Charlie now I have had a good think I am pretty sure the yellow leaves are due to me not giving enough water when the temperature and sun increased dramatically, fortunately that's easy to put right. As for the fert burn, well its only on some cv's, and its on the cv's that are prone to it anyway[Magnifique, Thanksgiving and Dark of Night [all the brown cv's].

But can I ask you 2 questions, first, I once read something you wrote[I think on your DVD] saying that 10% or a little of your water when watering should run out the bottom of the pot, now I have done that religiously once a week for years, but do you mean that a little should come out every time you water? Secondly I am very happy to hear that you think my feeding regime is low to moderate [half teaspoon of Booster and a half teaspoon of Ferilizer every gallon], I have been a bit worried about that, more worried for the long term life of the plant rather than its performance, but if you think ok I will carry on pretty much the same as up until now I have been very pleased with it.

[Charlie]

David, thanks for the photos, they help. They also do not show fertilizer burn. This type of leaf yellowing is classic for swings in temperature. In my greenhouse I get a flush of bright yellow leaves when the temperature swings either way - from hot to cool in early winter and from cool to hot in spring.

Keep in mind that hibiscus leaves are not supposed to be permanent. Hibiscus lose and replace their leaves many times over the course of their lives. This is the way hibiscus respond to their environment. It helps them deal with changes in light and temperature and water and is a last result for them when attacked by insects. In other words it is an entirely natural part of life for hibiscus. It startles us to see it change from being a gradual process of losing the occasional leaf to losing a bunch of them at once but usually it is not something to worry about, especially if you know what the leaf drop is being caused by.Some times you can do something about it - such as watering more or less - and other times you just have to wait it out.

Your other question was about watering 10 percent more than the pot can hold. This is an excellent practice to prevent fertilizer salts from building up in the pot. I recall reading a university study that set out to find out how much extra water was needed to leach salts from potting mix. The researchers tried a lot of different ways and in the end said that 10 percent excess water was very effective in removing most salts. Doing this once a week is plenty. I sometimes suggest doing it with every watering because that makes sure that the pot is actually being completely watered. A common new grower mistake is to pour too little water into a pot with the result that the bottom half of the root ball remains in very dry soil.

I think you should continue your fertilizer practice as before and continue with the excess water once a week. You should have no problems with your plants related to these practices. With all plant growing, the results are what matter. If you have healthy plants with green leaves that grow and bloom you can conclude that all is well.

Cindy just walked by and suggested that you look for spider mites on the yellow leaves. I don't think that is it this time but one should always check for mites when yellow leaves are on the rise and increase the dose of Kontos or use some other control method if you find them.

Let us know how it goes.

Charlie

[Charlie]

We probably should have started a new topic for discussion of the newsletter article. Maybe even a new board for Newsletter Discussions?

In any case, the article and interview with Darren was fascinating to me because Darren, being new to horticulture, really pushed the envelope with what is possible for hibiscus. If he had asked me first I would have warned him about possible damage to the plants but he went fearlessly ahead with an aggressive growing program and the results have been outstanding. Not many people will be willing to spray their hibiscus almost daily with Super Nova but I am now convinced that this is what it will take to overcome cold but not freezing winter nights. Nobody ever thought to try it until now - leave it to someone unaffected by established practice to do such a thing!

Hibiscus seem to have the ability to use quite a lot of nutrients both for growth and blooming. Knowledgeable people around the world have experimented with higher doses of things like Booster (KNO3) and gotten good results. Even so, there is a limit and once that limit is passed damage can be done. Darren has found what works for him but everyone has to find the limits in their own unique environments and be prepared for some damage if you go too far with it.

I love innovative thinking based on both real world experience and theory. Text book knowledge makes a great base to work from but it's still just a starting point, particularly with hibiscus that have not been studied much by the research community. They are fascinating and unique plants and we who grow them are the only "experts" these days. Funding for research goes to big ag crops like corn, cotton, etc and any left over research resources goes toward roses and other big cash making hort species.

Anyway, I appreciate what you did this past year Darren and I appreciate Chris in helping us put it in context. Theory plus experimentation drives the whole thing forward.
 
My 2 cents.

Charlie
 

[Ernest]

Charlie, your summation of the discussion is worth a lot more than 2 cents! I think you have framed the issues beautifully and put everything in proper perspective. Thanks to you, Darren, Chris, and David for an extremely valuable and interesting discussion. I for one would like to see more of these interchanges on other aspects of horticulture.

Erny

[helixturnhelix]

I understand that hibiscus specifically have not been studied extensively, but there has been a significant amount of data regarding plant physiology, inter-specific interaction, nutrient utilization using Arabidopsis and the crop plants mentioned by Charlie.  These plants are used as models and the information learned about them can be applied to many different plant species.  Without model species we would not have many of the advances in other fields of science, especially medicine.  Without model organisms, many of the discoveries which can be translated to other species, specifically human beings, could not have been made.  Fruit flies, Mice, Zebra fish, C elegans, E coli, African Clawed frogs, yeast, etc are all used as models for other species and mechanisms.  It is due to homology between species that such information can be translatable. 

There are defined models regarding nutrient uptake, and nutrient cycling which can be applied to hibiscus and soil communities in which hibiscus are grown.   I really think that if you throw away such work and data as being "not applicable", just because it is not specifically done in hibiscus is disappointing.

I have only tried to be objective and point out mis-information when I see it.  If "faith based" horticulture is what is going to be promoted here, I have nothing to contribute.   

[Charlie]

I'm not really following you, Chris. "Faith based" horticulture?

What we are doing could be described as the opposite of that. We clearly recommend the use of intelligent experimentation to gain insight into what works for hibiscus in every individual growing situation.

If I understand correctly, your main objection is to the fertilizing regime that Darren used. I agree that it could be dangerous or just unnecessary but it was part of the overall picture for Darren's garden during 2011 and up to this date in 2012. His results, based on the photos and bloom counts he made, were the result of everything that happened during that period of time. So, I included in the article all the facts that he provided us. Individually they can be criticized but as of this point it is not possible to separate out with complete certainty the irrelevant from the pertinent aspects of the program.

Personally I think that most of the results were probably due to the hormonal influences of spraying Super Nova several times per week for most of this period. Having a strong base of fertilizer nutrients for the plants to use probably helped. Was the fertilizer use overkill? Maybe. I would have said so but these results he got are really way beyond the norm. I'd like to take full credit for them by saying it was due entirely to the great HVH varieties, and in fact genetics does factor in, but the growth and blooming seen in Darren's garden during 2011-2012 both summer and winter was extraordinary. 

I don't want to address your environmental concerns because i think that is a separate issue that just confuses the discussion about what approach works best for getting hibiscus to grow and bloom. It's worth a discussion on its own but I don't think it helps in sorting out the current situation.

What I hope you and anyone else interested will do is design your own growing program, track it with observations and photos, and present it to the forum as the results come in. There is more than 1 way to do most things and that is for sure true about growing hibiscus.

Charlie