Men, Women, Botanist, lend me your ears!!

[Wayne]

PeteS and myself have been talking about the benefits of foliar spraying on Toms, Brugmansia's,etc.

Of late, through other's people research I've been spraying my cuttings with a weak solution of molasses, kelp , and sometime a splash of epsom salts to green them up so to speak. I do this because I want the best start and growing conditions for my plants.

But!!!!! :shock: Pete recently spoke with a chap who is a scientific adviser to a number of growers organisations, including the Tomato Growers .

He is of the opinion that foliar spraying is nonsense :o !! This was the conversation with a few edits!!

" I suggested that as plants make sugars and starches by photosynthesis, wouldn't supplying those make life easier for the plant. His reply was that photosynthesis makes the sugars inside the cells, and they have their own cellular transport system. Any sugars supplied from outside would be outside the cell walls. When plants are given a foliar feed of NPK chemicals, the chemicals ionise and being small, simple chemicals, they can with some difficulty pass through the cell walls. He then explained the precise mechanism - which lost me. However he said that sugars were large complex compounds, and that there was no way they could ever pass through the cell wall. So perhaps that's goodbye to another theory"

So what do think?? I am wasting my time foliar spraying, or are there indeed proven benefits to it.

I'd be interested in your views

Wayne

[kGarden]

I think PeterS was only referring to foliar spraying with molasses wasn't he? Conventional foliar feed nutrients are beneficial ... I think??

[Wayne]

It was the suggestion that the inner cells of the leave where unaffected by a foliar spray on the outer leave that caught my eye!!

Wayne

[David Matzdorf]

I'm aware that a lot of gardeners (as well as people who sell foliar feeds) swear that foliar feeding works. I've never done it, having been given advice very similar to what Pete/Wayne was told. It wouldn't surprise me if plants varied from one genus/family to another in their ability to take up nutrients through their leaf surfaces, but I have my doubts that it works for a large proportion of the hardy and half-hardy evergreen spp. that I grow. Same goes for those hormone spray treatments that were going the rounds a few years ago. I tried them and didn't think they merited the effort.

I haven't enough understanding of the physiology of plant leaves to be certain either way.

[AndyC]

I'm probably being dumb, but if a plant can take up a systemic weedkiller through it's leaves then why not plant food?

[Wayne]

Yes Andy, that's a fact!

I'm also thinking, that because Brugmansia's are a member of the Solanaceae family, they can be treated as Tomato's to some extent.
We know that Tom's are now mostly grown on mass using foliar feeds these day's.

I keep reading that it has been scientifically proven that there is a benefit to foliar feeding -I haven't yet read anything that really poo poo's it!! ;) in that plants can absorb nutrients through their leaves. And sure, some of the fertilizer solution which is sprayed onto the leaves falls to the ground and goes into the roots. So that's ok too!

Foliar feeding, as far I as see it, is a good boost to the plant , a vitamin supplement, while feeding the roots as the primary method for delivering nutrients, and feeding the surrounding healthy soil. Now that's another subject!!

Wayne

[Chad]

I think there are two issues here that are confused because historically we have been lax in the way we use words and which the first post here points out.

‘Plant food’ isn’t the same as ‘animal food’. On the whole plants ‘make’ their own food through photosynthesis. In animals the energy supply is from food in plants it is from the sun.

What we loosely call ‘plant food’ would be called ‘mineral nutrients’ in animals and can almost be thought of as ‘vitamins’ [though not chemically the same].

Foliar applications of small molecules are absorbed through the leaves; larger molecules on the whole are not. Those few larger molecules that can be absorbed through the leaves [one thinks of the systemic but sprayable insecticides] have special bio-physical properties that let them get in.

So traditional ‘plant food’ based on nitrates, phosphates and potassium can be absorbed through many leaves.

Sugars are quite large molecules, and have a lot of highly polar [a tendency to carry electrical charge] hydroxyl groups that make transport through the waxy cuticle of the leaves difficult. To get through the lipid cell walls requires specific transport mechanisms that are ubiquitous [transport of glucose is an almost universal feature of multicellular life] but is an energy dependent process; glucose is pumped across membranes.

Molasses isn’t even simple glucose. The sugar is sucrose which is two simple sugars joined together. Even for the animal gut to absorb that it has to first be digested down to the two constituent simple sugars.

There may be benefit in spraying molasses on plants but it is unlikely to be from ‘feeding’ them in the sense of supplying calories. It may be that molasses contains trace amounts of useful smaller molecules of trace nutrients that can be absorbed; it is known to be rich in calcium, magnesium, potassium, and iron. It may be that the by being dried out it leaves a strong sugar solution on the leaves that ‘sucks’ the water out of surface pathogens. I would fear though that it leaves a weak sugar solution that is a good food for pests and diseases.

There is some work on applying molasses as a soil drench to ‘boost’ the growth of mycorrhiza; from what I have read it didn’t work.

Chad.

[Wayne]

Thanks Chad,

It's becoming slightly clearer now :? ;) . The Molasses as you've said is more of a benefit for the other trace elements it has , such as the iron, calcium, magnesium, potassium.

I've used Molasses mixed with Kelp/Humic acid as a soil drench to kickstart my plants. I've been doing this for the past weeks, and the results are good so far.

Anyway, I'll continue to use a foliar spray mix, if anything spraying both the top and underside of the leaves will help combat the dreaded Red Spider Mite under the drying conditions of a greenhouse.

Wayne

[charlie]

I could see the Molasses having a similar effect to the spraying of certain vegetable oils for red spider control, seems to work by blocking up their breathing tubes (Chad can supply proper tech term!) but I prefer to think it glues the little b****rs to the leaves :D

[PeterS]

Thanks Chad for that explanation. That's effectively what the person I originally spoke to said. But its a good point about systemic insecticides. The original spokesman also said that there could be other things in the 'feed' that might be benefiting the Brugmansias.

SO - what suggestions are there for feeding Brugmansias.