Seaweed based fertilizers

mdahms1979December 9, 2010

I thought I would ask if anyone else is using seaweed based fertilizers? I recently picked up a bottle of concentrated kelp based fertilizer (2-2-7) and was planning on using it on my yellow Hoya villosa cutting. Today while caring for the plants I decided to use the fertilizer in the water I spray the plants in my grow case with, noticed a few more flower spikes going on in there, mostly orchids.

I misted my mounted orchids and Hoyas with the fertilizer and then I gently misted most of my Hoyas, hopefully this stuff gives them a boost. Today we are having another gorgeous sunny day with very bright light reflecting off of the snow, the first day that the city is operational again after a record smashing snowfall and we live in the snowbelt so we know snow. LOL

So anyone else using seaweed fertilizers? What do you think of them? The fact that you can soak cuttings and use this gentle fertilizer as a foliar spray for stressed plants has me interested in what others experiences have been with similar products.


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geosdee(Zone 8 FL Panhandle)

Hey Mike,

I haven't used that before but have used the Alaskian fish emulsion. Where did you happen to get it and what is it called. I did order the folage pro but haven't used it yet. I would be curious about the seaweed myself. It seems like this whole country seems to be getting a big whollop of snow and cold. It was 24 degrees F when I left for work yesterday morning and I live in the Florida panhandle. Now we do get cold but this is just too cold.


    Bookmark   December 9, 2010 at 2:44PM
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Dee I use fish based fertilizers as well but I plan on using this Kelp fertilizer as a foliar spray vs a pot drench for the roots. I got my seaweed fertilizer at a hydroponics store, they had made up small bottles for sale so you did not have to buy a big jug. The stuff is super concentrated so you only need a tsp per liter of water.
It is still very wintery here but no snow has fallen today. The temperature is not that bad, only about five below freezing and we are used to low around twenty below when it's really cold.


    Bookmark   December 9, 2010 at 6:22PM
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Mike, I use a product called ocean magic.Its an all natural marine algae extract plant food.I got from a hydroponic store also.I have used this stuff as a foliar spay but stopped when I noticed some of my hoyas leaves starting to get some pitting.I now use it to root water.I also use B52 in my water.


    Bookmark   December 9, 2010 at 7:09PM
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greenman28 NorCal 7b/8a

Mike, I've never used kelp based products, but I'm not opposed to them in any way.
In general, however, I prefer to use organic products outdoors during the main growing season.

I have heard that most plants can't absorb most nutrients through their foliage.
With the Epsom salts, if you *do* notice a positive effect, then a root-feeding is indicated...
and far more efficient a method of delivery, besides.

I'm a chronic under-fertilizer, truth be told, but I'm getting better ;)
This time of year, a 1/4 or 1/8 strength dose of a balanced fertilizer is great for maintenance.
I use Foliage Pro 9-3-6, which contains all the micros, for all of my plants,
indoors and out. Makes it super simple.


    Bookmark   December 9, 2010 at 9:46PM
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Hello everyone...I don't use Fish Emulsion or Seaweed for the purpose to fertilize my plants, but to keep the leaves shiny, clean, and pest free.

Do all of you using FE on the leaves ever notice the lack of pest's on your plants by the time winter comes? I do..Mine are always pest free when I spray my leaves on a continual basis with these natural oil base products..

Just curious..

Josh..Hello! I use the same you do to fertilize all my plants and they have never been so happier..


    Bookmark   December 10, 2010 at 8:10PM
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Cindy thanks for the tip, I don't often mist my plants so maybe I will keep it that way. I think this fertilizer will be great to use on my mounted plants though because it's super easy to mix in my little pump sprayer.

Josh I don't think most plants can absorb much in the way of nutrients on the leaf surface either, most have that waxy cuticle and after all it's there to protect the leaf. I have heard that the underside of the leaf can do a better job at nutrient absorption but it's still probably not that good. The interesting thing about kelp fertilizer is that it is supposed to be full of plant hormones as well and because kelp is one of the fastest growing plants it might play an additional role, not sure if it is easily absorbed though the leaf or not.
I might have to look for that DynaGro Foliage Pro, looks like a good fertilizer. I used to use DynaGro on my orchids before I switched to organic fertilizers.

Mike that's interesting about the natural oils in the fish emulsion fertilizers preventing insects, makes sense. How long have you been using this type of fertilizer as a foliage spray?


    Bookmark   December 10, 2010 at 11:51PM
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@greeman28, mikedahms
Plant absorption of nutrients through the leaf is well documented but varies among plant species. You are certainly correct that a thick waxy cuticle is less permeable to nutrients and hormones, but even hydrophobic waxy leaves such as those of banana plants have been observed to rapidly absorb dissolved compounds.

As for as permeability of leaf waxes goes:
esters > fatty acids > alcohols > triterpenoids > hydrocarbons
(Baker & Bukovac, 1971)

For dissolved elements:
Cesium > Rubidium > Sodium > Lithium > Magnesium > Strontium > Calcium
(Halevy & Wittwer, 1965)

As far as plant hormones go, most of these chemicals are carboxylic acids or alcohols, although some are steroid based. Leaf absorption of these compounds would follow those listed above.

    Bookmark   December 11, 2010 at 12:57AM
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Forgot to post source:
Riederer M & Muller C. Biology of the plant cuticle. Annual Plant Reviews. 2006; 23.

    Bookmark   December 11, 2010 at 1:54AM
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Thanks Rennet :)


    Bookmark   December 11, 2010 at 8:49AM
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Hi Mike...

I have been using FE as a preventative for a few years now, but not every summer..In the seasons I did not use it, my plants had pests all winter I had to deal with, especially scale, thrips, and spider mites...

I stuck to the regimen of spraying the leaves all summer into the time I brought them in this year, at least once every couple of weeks, and they are all pest free again..I can't guarantee that it will work for everyone, but it has worked for me the ones that I know..

I have never had to use it to rid a problem already in progress, just to prevent one, but it may rid the problem too..If anyone decides to do this, I would love to know..


    Bookmark   December 11, 2010 at 6:57PM
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greenman28 NorCal 7b/8a

Here are a couple passages that Al (Tapla) wrote a while back on the topic of foliar feeding.
Anyhow, this will be a refresher to some, and new information for others. Al explains it all far better
than I ever could ;)

"From the perspective of getting nutrients from outside the plant, inside the plant, foliar feeding is generally extremely inefficient. In those plants that benefit from foliar feeding, fertilizers in ionic form are far more effective than various emulsions/suspensions at providing supplemental nutrition, but roots are still, by far, the more efficient and reliable pathway. If your plants actually NEED foliar feeding - by default, there is something wrong with your basic nutritional supplementation program and your efforts are best concentrated there.

Foliar feeding is usually only used effectively to supply a few elements in ionic form (mainly N,Fe,Cu,Mn,Z), and only when plants that are able to provide a foliar pathway into the plant are growing so rapidly the nutrient stream cannot supply certain nutrients fast enough."

And from a different Thread of fertilization:

"The effectiveness of foliar fertilizers varies to the extreme. First, only some plants can absorb ions (and a few small proteins of little significance) through their leaf cuticle and allow them to enter the nutrient stream. This means that only soluble solutions or the minuscule ionic fraction of organic fertilizers like fish emulsion are able to pass through the cuticle of SOME plants and make it to the nutrient stream. Fish emulsion depends on micro-organisms in the soil to break it down into elemental form so it can be absorbed. These organisms are not present in measurable populations on foliage and would lack the moisture necessary to keep them viable anyway, so foliar applications of FE and other organic amendments are not measurably effective as a foliar spray.

[...] Any fertilizer that supplies nutrients via foliage as the primary pathway would supply the same nutrients via normal root pathways.

Note that many nutrients are immobile in the plant (mostly micro-nutrients and Ca), so quick fixes like adding Fe (iron) via foliar applications may green up the leaves temporarily, but do nothing to actually relieve the deficiency the entire organism is dealing with."


    Bookmark   December 11, 2010 at 11:11PM
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Thank you so very much for this information and reminders..

I have learned a lot from threads like these, and Know I know why foliar feeding was a waste of my time, especially on these plants...

No wonder past reliance on foliar feeding for "fertilization" purposes on most of my plants, never did a thing for mine..

Much appreciated


    Bookmark   December 12, 2010 at 9:39AM
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I use kelp for outdoor and indoor fertilizers. Outdoor - as a part of Solomon's organic fert(use blender to grind it up) for veggies, and for indoors I add a few drops of a home made extract every time I fertilize houseplants. On the beach the kelp is free for taking.

    Bookmark   December 12, 2010 at 8:42PM
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geosdee(Zone 8 FL Panhandle)

I have started using the Foliage Pro. I have to say that I do see a difference with them in the house ths winter compared to last winter. I am misting them with this stuff about once a week and they don't seem to look as drab I guess the word I am looking for. They seem to perk up with this stuff versus just misting them with water. Imagination or not I will continue to use it.


    Bookmark   December 14, 2010 at 7:54AM
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