Foliar spray?

[shafak]

Are all tropical fruit plants and trees benefitted equally by foliar spraying or are there some which benefit more than others?   Thank you.

[shinzo]

Interesting question, i am brewing a liquid fertilizer with borage (a cousin of the comfrey) rich in potassium and Nitrogen, and was planning to dilute it (5%) and spray it on guava, papaya, passion fruit and mango leaves. I hope this will benefit to all of them. i did the same one week ago with nettle tea and i noticed a good response with the passionfruit, a relatively weeker response for the papaya and guava, but it has been only one week since i started the foliar applications, i hope to keep spraying twice a month and see what happens. (just to know, i  am also planning to water the plants with these liquid fertilisers diluted to 10% twice a month)
PS : this program i mentionned is an experimentation of my own started last week, i don't know if it is ok or too much, i am planning to apply and monitor. just so the things are clear to unexperimented readers (like me) because i don't want to induce anyone to mistake. unless this application schedule is backed up (or corrected) by more experienced people here.

[Tropicdude]

I'm thinking any plant that generally has a poor root system,  for example mangosteen.  will probably benefit more than others.   also,  reclaimed land with poor soils, that need to be built up, plants in those areas would probably get more benefit.   and plant that have had their roots cut, or plants that were propagated through air layering.

[treefrog]

duplicate removed

[treefrog]

bromeliads - such as pineapples -  don't have much of a root system.  some bromeliads have no roots at all (spanish moss). 
orchids have aerial roots.  all these are good candidates for foliar feeding.

i have a home made mix:
2 cups kno3 (potassiun nitrate - aka saltpetre)
1 cup mgso4 (magnesium sulfate - aka epsom salt)
i tablespoon tripotassium phosphate
1 tablespoon trace element supplement

i use a teaspoon of this mix dissolved in a liter of water. 
there's some kind of grit in the trace element supplement that eats the  pump in my hand sprayer.  i let the dissolved mixture stand overnight, then strain through a paper towel.  that eliminates the grit problem.  for pineapples, i add a few drops of liquid chelated iron to a liter.

light, dilute applications at frequent intervals (weekly instead of monthly) seems to work better than heavier doses..

[shafak]

Thank you for the replies.   Could you please elaborate what is a poor root system? Where can I learn about which plants have what type of root system?