Mike Corazzi
Masterpiece
.......should foliar feeding be more of a priority than other species?
If juniper energy comes from the foliage........
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grouper52
Masterpiece
Uhhhh ...... not sure about the premise of the question .... all photosynthetic plants I know of rely on their foliage to generate stored and immediate energy for growth. With the exception of some rather gradual thickening of the cambium, and less so of the sap wood, leaving behind inert heartwood, the active growth itself takes place in trees almost exclusively in foliar buds and root tips. There may be some special reason why junipers prefer to absorb nutrients through their foliage rather than their roots, but I've never heard of it, and it is certainly not what they would be accustomed to do in nature. I'd be happy to be be proven wrong, in this regard, although my junipers and those of others I know seem never to have suffered nor wanted for vitality due to lack of foliar feeding. 
Forsoothe!
Imperial Masterpiece
I'm not sure calling the exterior of Palo Verde "bark" is appropriate. It's so specialized as to be as functionally unlike as possible to what we refer to as "bark". Seems to me that they are more like a giant long skinny sub-divided leaf. Do really old PV evolve something that looks like "bark"? Bark transpires but hardy uses sunlight to photosynthesize. The young stems of lots of woody plants have yellow, red or green stems that are high in chlorophyll and photosynthesize, but that's a stage that eventually is passed through on their way to "bark".
I'm not qualified to speak to the matter scientifically, but I'd bet that almost all of the benefit from foliar feeding occurs via the liquid fertilizer eventually being washed down onto the surface of the soil immediately surrounding the plant and being absorbed through the roots. I've done extensive foliar feeding and the deposits on the leaves obscure any increase in "greeness" that may or may not accrue.
I'm not qualified to speak to the matter scientifically, but I'd bet that almost all of the benefit from foliar feeding occurs via the liquid fertilizer eventually being washed down onto the surface of the soil immediately surrounding the plant and being absorbed through the roots. I've done extensive foliar feeding and the deposits on the leaves obscure any increase in "greeness" that may or may not accrue.
Gsquared
Shohin
I’ve frequently heard the benefits of foliar feeding with junipers, but I really don’t know of any science behind it. Definitely open to learning if is indeed a real thing. What I keep thinking though, is how would it work? Stay with me here: carnivorous plants, specifically pitcher plants or butterworts, require digestive enzymes (or symbiotic bacterial action) to break down the dead bugs to a useable form where they are absorbed to feed the plant. Okay so those are definitely foliar feeders. But would spraying fertilizer be beneficial to a juniper, which I would think have no digestive enzymes to aid absorption? I’ve periodically tried it, mostly on the lower branches and cascades of junipers. I would try it for an entire season then not the following year to see if there was any visible change from year to year. Frankly, I never saw a difference.
Everything I have read calls it bark. It is specialized but bark is the appropriate word for it.
Tree Bark (Botany): Definition, Function and Uses | Biology Dictionary
Bark, often “tree bark” in botany, means the outer covering of woody plants. Woody plants, unlike herbaceous plants, create an intricate framework of cells and fibers, which provides significant support and protection. Bark is the woody exterior of this structure. Technically speaking, bark is...
one_bonsai
Shohin
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I agree. I think foliar feeding is a myth. Plants can absorb nutrients through their leaves but not to any significant extent. This makes sense because leaves are designed for gas exchange. The roots are specifically designed to takes in nutrients. So why would you apply fertiliser to the part of the plant that's not designed to absorb nutrients?
Wires_Guy_wires
Imperial Masterpiece
Absorption is passive (based on electric potential), the enzymes are used to break down the insects. Proteinase, chitinase and many other enzymes aid in digestion and without specialized 'glands' or microflora to produce those, feeding insects to plants isn't going to do much good. Dissolved nutrients however, require only a potential difference to be taken up. That's why it's so easy to kill (overfeed) carnivorous plants with nutrient solutions; they take it up so easily that they screw up their internals.
Try a solution with micronutrients like Iron and copper, and you can clearly see a difference in foliar color in most plants after a single application. Foliar feeding can help to some extent, but a healthy and well fed plant is more likely to not show any effect from foliar feeding. One thing in junipers especially, is that they have a thick cuticle; a layer of wax to prevent them from losing too much water in dry heat. This cuticle also repels water with nutrients. Still, they can take up some nutrients from foliar sprays. Especially on cold(er) and humid days, when the stomata are fully open. Gas exchange is one thing, but along with oxygen, plants breathe out water too. Wherever there's water, there's transport.
But.. There's a general rule with many plants that if you're going to offer fast food, they're not going to keep their own kitchen running. If you want strong root growth, it's better to enforce the plant to invest in the nutrient highway instead of offering shortcuts through the foliage. Some plants do not root at all in nutrient enriched media, simply because there is no need for them to invest in root systems; the passive uptake is enough for them to thrive and investing in roots is a costly side business. I have one of those plants, and after close to 400 cuttings in various media with various amounts of auxins, cytokinins, other hormones and nutrients, I've found that the best way to multiply them is from seed and seed alone. The cuttings grow and thrive, but they never root.
And let's be honest: who is going to do grocery shopping after having some pizza delivered? Plants make somewhat the same decisions.
One potential benefit of foliar feeding is that the nutrient solution kills some bacterial and fungal flora that aren't used to those high salt levels. Those could be beneficial flora, but they could also be pathogens.
I think the true answer isn't as easy as IF this, THEN that.. I mean, if plants wouldn't take up nutrients through their foliage at all, you wouldn't be able to kill them with highly dosed nutrient solutions.. But we can. If plants would take up a whole lot of nutrients through their foliage, then they wouldn't need roots in rainy and wet locations, but they do.. Leaf disc cultures are still a thing in the scientific plants world and that same field of science has 'decrease amount of nutrients' as the number one answer to plants not rooting.
Foliar feeding should not be a priority. The priority should be to have a healthy system inside the plant, where everything works as it should. And when everything works as it should, foliar feeding isn't necessary.
one_bonsai
Shohin
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How do you know that the change in foliage colour isn't due to the fertiliser dripping off the leaves and onto the roots?
Wires_Guy_wires
Imperial Masterpiece
Because not all plants have foliage directly above the pot. If you don't soak your entire plant, 25 drops of liquid will not penetrate the soil deep enough either, the dripped down nutrients require a good watering to come close to the roots.
To answer your next question: how do you exclude the nutrients themselves producing that color?
By hosing the plant down the next day with excessive amounts of water and observing the color stays the same.
one_bonsai
Shohin
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M. Frary
Bonsai Godzilla
Don't know if it helps but it doesn't hurt.
I do it.
Sansui
Shohin
I suppose foliar transpiration is bi-direction but maybe less so with needled trees because of their waxy coating to conserve moisture? Just guessing here. I found this paper that may be of interest to you:
penumbra
Imperial Masterpiece
So much contention over such a simple thing indicates that almost no one has done a side by side study. I have, but it was 50 years ago and I can't remember all the particulars. Actually my first real job was at a nursery when I was 13. Everything was foliar fed every week. There was no buildup on leaves which seems to indicate that it is probably more the water than the fertilizer, but there is explosive growth.
Today, I do foliar feed to runoff maybe once a month at most. But I foliar feed frequently using a simple compression sprayer. Liquid kelp is my favorite product for this. I have learned that a regular spay on the foliage of fruit trees inhibits fungus growth and encourages new growth, as well as helping repel insects. For the fruit trees and berry plants I use kelp with fish emulsion so the repelling of the insects could be the fish, but I think it is the kelp that is mostly responsible for pushing new growth.
All of my houseplants, tropical bonsai and orchids also get foliar fed, with the appropriate fertilizer, but barely to the point of runoff and often intentionally less in the case of many of my succulents.
The problem with an issue such as this, like others, is that people are so passionate about the beliefs or disbelief's, that is becomes a battleground like religion, politics or even sports. So it doesn't ever boil down to the real issue. I was going to stay out of this fray, but I humbly present my own thoughts which are based upon my own experiences.
Today, I do foliar feed to runoff maybe once a month at most. But I foliar feed frequently using a simple compression sprayer. Liquid kelp is my favorite product for this. I have learned that a regular spay on the foliage of fruit trees inhibits fungus growth and encourages new growth, as well as helping repel insects. For the fruit trees and berry plants I use kelp with fish emulsion so the repelling of the insects could be the fish, but I think it is the kelp that is mostly responsible for pushing new growth.
All of my houseplants, tropical bonsai and orchids also get foliar fed, with the appropriate fertilizer, but barely to the point of runoff and often intentionally less in the case of many of my succulents.
The problem with an issue such as this, like others, is that people are so passionate about the beliefs or disbelief's, that is becomes a battleground like religion, politics or even sports. So it doesn't ever boil down to the real issue. I was going to stay out of this fray, but I humbly present my own thoughts which are based upon my own experiences.
Wires_Guy_wires
Imperial Masterpiece
I can dissolve dessicated micro-nutrient solutions even months after they've dried up. I don't see your point.
penumbra
Imperial Masterpiece
Forsoothe!
Imperial Masterpiece
Precisely
grouper52
Masterpiece
Interesting! Didn't know that. Is it true that there is some special benefit with foliar feeding then in that species.
0soyoung
Imperial Masterpiece
Ever wonder why the cambium is green in most species?
sorce
Nonsense Rascal
I have an answer, but first, let me remove this pancake off of my head.....
Ok, I'm still hungry.
Fertilizer company's aren't in the business of making your plants grow better, they are in the business of selling fertilizer. The more you waste, the more you buy.
That said, if you wet the foliage with fish emulsion, which seems to be the most popular, you gain other indirect benefits.
Wasps, which eat other tree damaging pests.
Flies, which attract spiders, which eat other tree damaging pests.
If you ever watch what happens to the fert when you put it on, it's pretty clear, with simple observation (as always), that it doesn't really do anything.
Besides, when it rains, it rains, clouds never get diarrhea, and trees have been growing well for millions of years.
Humans are gullible ain't it?
$$$$
Sorce
Ok, I'm still hungry.
Fertilizer company's aren't in the business of making your plants grow better, they are in the business of selling fertilizer. The more you waste, the more you buy.
That said, if you wet the foliage with fish emulsion, which seems to be the most popular, you gain other indirect benefits.
Wasps, which eat other tree damaging pests.
Flies, which attract spiders, which eat other tree damaging pests.
If you ever watch what happens to the fert when you put it on, it's pretty clear, with simple observation (as always), that it doesn't really do anything.
Besides, when it rains, it rains, clouds never get diarrhea, and trees have been growing well for millions of years.
Humans are gullible ain't it?
$$$$
Sorce
