foliar

They use foliar sprays which urges plant leaves to develop filament like needles on leaves turning them hygroscopic.

There's a thing called foliar spraying, where you do spray water and nutrients on the leaves.

People use rooting hormone and foliar sprays of plant growth regulators and such, but they do that in soil too.

Pyrethrins aren't exactly safe for bees either, with both being broad-spectrum insecticides and requiring more frequent application via foliar spraying.

As a foliar spray used in the garden, it works wonders against fungus and bugs.

It’s possible they were doing a foliar nutrient spray, to keep the trees greener/healthier.

Unfortunately, surface applied ZnSO4 does not rapidly leach into the rooting zone soil, and foliar Zn sprays are ineffective in reducing Cd in beans.

For example, foliar nutrition in AMF Ambrosia artisifolia L.

Likewise, in mono-specific pairs of EMF interior Douglas-fir grown in greenhouse conditions, foliar micronutrients were increased in kin compared with strangers grown with older conspecifics (Asay 2013).

There are plenty of alternatives for protecting food crops from insect infestations, such as neem oil applied as a foliar spray or a soil soak in response to infestations.

There's no reason to water the leaves rather than the dirt around the roots, unless you're applying a foliar spray or watering something like a tillandsia that doesn't normally live on the ground.

This leads into weird scenarios where things like some ordinary phosphorus foliar fertilizers have a mild antimicrobial effect (I believe mostly against fungus, but I don't recall clearly) and everyone knows it.

Even though the injection process is initially time consuming, it is more cost-effective than several trips to the same site for foliar applications made over years with minimum results." --- None of these studies mention the specific technique of using stem injection with imazapyr, which I think is likely to be the most effective method.

Foliar isn't about hydration state, it has chemicals and surfactants and it's recommended to do it in morning/night.