I was looking into fish fertilizer for seedlings ( fish-fertilizer-t3140.html ), and was perusing the Neptune's Harvest website, where they encouraged using it as a foliar spray.

My gut reaction to any kind of foliar spray other than insect or blight control is...that's crazy! I don't want my tomato or ground cherry and I guess peppers and other stuff to be any wetter than they have to be, I have enough foliar disease problems as it is.

Or do people do this? I searched the forum and didn't find too much talk about it.

I do not do this, but I would imagine, if you applied it a bit after sunrise so the leaves would dry out rather quickly, it shouldn't pose much more of an issue than the morning dew?

Maybe do 4 plants of the same type if you have the space, two without foliar feeding and two with and see how they differ?

I don't do this, either. It makes no sense to me, to spray fish or other fert/manure on tomatoes I'm going to eat.. Not even on the flowers. Nuh-uh.

I believe foliar feeding was invented by birds. They sit on the tomato support at mom's garden and they let fly the guano. Luckily their coverage is not uniform like an overall spray applied on purpose. You just find these telltale white splotches upon a random leaf. And of course, the rain washes it off eventually.
Do the plants like it? They don't seem to mind. It is extra fert after all. The science says they can absorb some nutrients directly into the leaf. Most of the bird stuff probably gets absorbed via the roots, anyway, after being washed off into the ground - which is where I like to put the fertilizer, just to stay ahead of the birds.

I love foliar feed. Yo can change your plant in matter of days with minimal amount of ferts.
Been doing it for years. It is not a substitute for soil feeding. But boy does it work!
I go by Smiling gardener recommendations.
https://www.smilinggardener.com/sale/or ... rtilizers/

I do it a lot (as of 2021; I had done it before that, but not a lot) with water-soluble fertilizers, such as Miracle Gro (24-8-16 All-Purpose), calcium nitrate, and potassium sulfate. I find it very rewarding (on tomatoes, peppers, watermelon, our nectarine tree, roses, Sempervivum, blackberries, cucumbers, zucchini, etc.) However, we have low humidity, and foliar fungal problems are not terribly common. I've never had a problem with foliar feeding causing disease in the garden, in my climate, to my knowledge.

You have to be careful to spray when the sun isn't out, or it can burn your plants. Early morning sun probably isn't as big of a problem, but I don't like to risk it, personally.

I've experimented with foliar sprays on houseplants, and while that works, it can leave a residue on the plants; fertilizing the soil is probably a better idea in most cases, for houseplants; foliar sprays tend to have faster results, though (but fertilizing the soil will provide more fertilizer over-all, to a houseplant; for a garden plant, it's more complicated, since the roots aren't all at the base of the plant, and soil pH is a bigger concern for ground fertlization). I have noticed a nitrogen foliar spray causing disease-like symptoms on some of the new growth of an indoor potted umbrella tree, however (but not any garden plants). The symptoms went away after a few more leaves grew; I think it was more the nutrient balance that caused it rather than the moisture, in this case, but I imagine in a more humid climate where it gets warm and wet at the same time, where plant-infecting fungal spores thrive, it might be a big problem.

I've never used fish emulsion in a foliar spray. That idea scares me, but I imagine it can work.

Before 2021, I mostly just used foliar sprays on pre-transplant seedlings (which can be even more helpful than I realized before 2021). I had done it on some other things, but not a lot.

To answer your question, though, I don't know too many people who do it, besides me. The people I do know who do it usually attach a nozzle to a garden hose and foliar feed that way. I don't do that, since it's less efficient and requires more setup time and thought (but once you get started, it's fast, at least).

Commercial entities probably do foliar sprays a lot, though.

If you get much rain, you might consider doing the foliar spray right after it rains, when the plants are already wet. Using more potassium should be helpful to some degree if disease is a concern (but not more nitrogen), however you administer it. Same for a few other things.

I have no hard data for reference but I am not a fan of foliar feeding and I never do it. I believe that plants are designed to absorb nutrients through their roots so when I use any ferts I apply them to the soil.

I did an (admittedly unscientific) trial last year. I used Microlife 3-8-3 foliar feed on one container cherry every week. Then I poured the exact same mix and quantity on the soil of the plant next to it. At the end of a couple months there was no visible difference in the two.

They were two different varieties unfortunately, wish I had two of the same to do it on, but oh well. Since then I’ve only fed the roots.

I like foliar feeding. I like to use fish emulsion and will use liquid kelp and other foliar fertilizers.

Seems like the fish emulsion gets the tomato sets once they get planted out in the beds going well for me, then I back off the fish emulsion in favor of something foliar with more phosphorus as the plants start to get some size to them. The Kelp foliar spray seems provide some buffer against and provide micro nutrients to help battle blossom end rot, blossom drop and other nutrient uptake issues and physiology issues. I haven’t been getting BER to any degree in recent seasons and I give the kelp emulsion part of the credit.

I find it harder to get granular soil fertilizer dialed in correctly and don’t really like to do the granular supplements in the ground as the season progresses, not wanting to fiddle or tamper with the mulch layer and disturb roots. The foliar spray is very easy to measure and dilute to the level you desire and very quick and relatively painless to apply.

I’m going to keep on keeping on with the foliar feeding.