leaf above the fruit: myth or fact? evidence?

[bower]

Read, heard or somewhere got the guff that the leaf immediately above a fruit cluster is the one that provides it with direct nourishment. Hence when pruning hard, you may take all but those most important leaves, so it goes.

I'm trying to prune hard, and I definitely need to prune harder, but it does seem that the very leaves I want to snap off are the ones right above a cluster. That can't be good can it?

Should I take all the others but spare that 'above the cluster' leaf? Even if it's badly positioned or too enormous and droopy or....

Anyone experiment or have a tale to tell?

[Salsacharley]

I don't know about the nutrition aspect of the leaf above a cluster but that leaf would be best to prevent sun scald from my viewpoint.

[zipcode]

I think the idea was that that leaf is more important than others for that cluster. Not sure if there is any published data, but since big commercial growers do it there must be some results somewhere.
I personally think that a good amount of leaf is important for great taste. Plants that were overly vegetative in the beginning and had big leaves and rather thick stalks usually ended making the tastiest fruit.
On the other hand, a test using various rootstocks for same variety showed differently. It even has pictures showing a much more abundant 'leafage' on the grafted ones, slightly higher yield, but the panel said the fruit tasted worse.

[bower]

Tx guys. I did think about the sunscald issue, but not sure if that is as big a concern as too much shade. We've been having a pretty awful spring and tied the record for cold in the first half of June - that has included a lot of cloudy days when temperatures in the greenhouse are cool if not downright cold.

So the 'above fruit' leafs (and others of course) have gotten huge in those conditions, while the green fruit have been growing slowly or not at all (only on the good days) although many have been hanging for long enough to be ripe by now if temperatures had been normal.

My biggest concern is that I'm getting aphids in places where the leaves are too thick/overlapping. The spacing is tight so I will have to prune somebody's leaves to let air and light in which seems less ideal for the aphids.... I normally prune very little, so it's a struggle to figure this out...

[GrowingCoastal]

"Read, heard or somewhere got the guff that the leaf immediately above a fruit cluster is the one that provides it with direct nourishment. Hence when pruning hard, you may take all but those most important leaves, so it goes."

This is what I was taught by someone who had agricultural training at Guelph. That was in the '70's but I have never heard different. If your upper leaves are too big how about compromise by removing only the 1st, or lowest, part of it?

[SueCT]

I understand about the aphids, but not the shade/sun part. I don't think the actual fruit needs any sun to ripen. It is the plant and leaves that need the sun, and the plant sends the signal to the fruit to ripen, but sun directly on the fruit is not only not needed, but bad for it. The cool temps might be slowing down fruit development, but those fruit are simply not going to ripen until they are developed and the plant tells them to, direct sun on them or not. The only thing I have ever seen cause them to ripen more quickly is stress, when the plant thinks it is dying and needs to ripen fruit quickly to produce seeds even if the fruit isn't developed. I have seen even small fruit start to ripen at the end of the season, but it is not desirable and is not very good tasting fruit. Forcing undeveloped fruit to ripen will probably always effect taste. It simply needs the time and correct conditions to develop the flavor.

[PaulF]

Sorry, I just don't understand the reasoning behind pruning any but bottom leaves to keep them off the ground. My laziness is showing, but no pruning means less work and I have never had a complaint about either production or flavor of tomatoes that have not been pruned.

[SueCT]

I think her biggest issue is aphids.

[oakley]

I'm wide open to all growing conditions/environments.

What works so well for others is not going to work for some stretching their season.

I know first hand about Newfoundland and friends that grow in St Johns in high tunnels and
greenhouses. Impressive to have any fruit set now.

When I skim or dive into an article be it a University controlled study or a parroting article
written by a copy writer, (most do not even have or have ever had a garden)....I know a few,
I tend to visualize the information applied to a plant.

The plant needs the leaves but does it need that one, (?), bottom leaves no. Early fruit set and
flowering is fine before sun scald could cause a problem? I would remove a big potato plant leaf
but not all of them.

Real estate. I want quality and like to trial many varieties.

Let Mother Nature do as intended? Yet nothing is natural about starting seeds indoors
under lights or on a heat mat, or many of us would
not have any tomatoes at all and I'm harvesting cherries now.
Unheard of if I followed a recommended formula.

I so get the questions Bower is asking. Advancing crosses etc.

[SueCT]

I understand her reasons for asking, I just think a couple of her assumptions are wrong, such as sun directly on fruit ripening it more quickly. Not seeing the actual plant, if she has overlapping leaves, there should be no harm in removing one of those leaves to aleviate that if she thinks it will help for aphid control. But using it to exposd fruit to direct sun to ripen it more quickly I don't think is based on a correct assumption. Hopefully someone with more scientific knowledge about the process will let her know if this is correct or not. But from this site: https://newfoundsander.wordpress.com/seasons/ it looks like New Foundland has seasons very similar to New England. If that is the case, having fruit set this early at all is not only not late, it is early. I have no fruit set at all yet. So they actually seem to be doing well. However, since I have little credibility as a non scientist, I thought I would share this. "Light conditions have very little to do with ripening. Tomatoes do not require light to ripen and in fact, fruit exposed to direct sunlight will heat to levels that inhibit pigment synthesis. Direct sun can also lead to sunscald of fruit. Do not remove leaves in an effort to ripen fruit." Cornell is usually considered a reliable resource.

https://cvp.cce.cornell.edu/submission.php?id=91

[nbardo]

I’d bet there is some truth to it but it’s probably more complicated than that. Early in the season when theres lots of vegetative growth and fruits are still small, plants are sink limited meaning they are producing more sugars and other chemicals than they can use up by pumping then into fruit and seed production. Later in the season under a high fruit load they are source limited, meaning they are using up all the food they can produce and the result can be smaller or less flavorful fruit. There have been studies done comparing size of fruit with the number of competing fruit on the same truss or a nearby truss that show there is competition between nearby fruits for the same resources, both within the same truss and on nearby trusses. To me that says that this sink/source ratio isnt constant throughout the whole plant, and if you prune away all the leaves around a truss it will have to compete for resources from further away leaves that are closer to other trusses.

All that said, if you are looking for leaves to remove it makes more sense to do it for a reason than to worry too much about which fruit it is closest too. IE it makes tying to the stake difficult, it makes the plant too dense, it has a spot on it, etc.

The only way to know for sure is to test it!


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[bower]

Thanks so much all of you! Really appreciate all the points of view.
@Coastal, thanks for referencing someone with ag training - I knew I read it somewhere believable, but couldn't recall the source, so long ago..
And yes, I 'munched' a few half leaves instead of taking the whole thing, when I realized I was thinning the wrong ones... then I stopped to ask you folks for advice.
@SueCT, really helpful point about NOT exposing the fruit to too much sun, and sun NOT helping to ripen (I do want them to finish growing first btw!
@Oakley and Sue... yes I planted extra early, got a few weeks of glorious weather but that was followed by the doom, last week of May and first two weeks of June which tied the coldest on record. It's a test, I am pushing the limits. But all my experimental (unstable) plants had 9-17 fruit pea size or bigger by the 100 day mark, except one with 35 and a couple of late outliers with only 4-7. We'll see if the fruit are fit to eat or not, when the time comes.. Everything has its limits.
One thought about the sunscald, if there was a way to change the weather to sunny and hot, it would be to prune off all those sheltering leaves! As Murphy's Law does seem to rule the weather here to a great extent.
@PaulF, I will find or take a pic to show you just how my planting scheme is spaced this year... very tight and that too is an experiment...

[Salsacharley]

If you want to avoid sunny and hot weather to reduce sun scald, you should wash your car!

[bower]

Originally Posted by Salsacharley

If you want to avoid sunny and hot weather to reduce sun scald, you should wash your car!

Yeah! I just hang my laundry out... panic:

[Nan_PA_6b]

Last year, I grew an Anna Maria's Heart tomato plant. It got quite diseased. I took off all affected leaves, until the leaves were getting very sparse. I decided I'd leave 3 leaves on the plant, even if they were diseased, in order to help ripen the fruit. I left on the 3 with the most green. These were all above the fruits. The plant went on in this manner for a couple months. And the fruits were tasty!
Nan