Which Fertilizer for Larger Fruit

Most of my orchard is in its 4th and 5th leaf. When first planted I reworked the soil so that it is mainly planted in a modified raised bed style.

I have apples, pears, peaches, plums,nects, apricots and a variety of apriums plumcots etc.

The trees grew well and fruited but… Now I find that some of the fruit themselves don’t seem to be as large as they should be and I don’t think that all of the size issue is attributable to insufficient thinning ( although I plead guilty to some of that charge)

So my question is… Is there a Fertilizer regimen that is targeted to increasing the size of the fruit. And when to start it here in the Northeast. And I promise more aggressive thinning.

Hey @alan, @olpea, @Richard, @scottfsmith and anyone else who I overlooked



If you fertilize more and water more for larger fruit you are going to lower the brix and IMO the flavor. Thinning more can increase size and brix.


I disagree with FN and recently a CA grower spoke of his very high brix June Pride peaches accomplished without serious water deprivation early in the season. Research I’ve seen shows that N. does not in itself affect brix levels- at least with apples- lots of summer water does. The grower attempting to get size AND quality is best served by a quick release N in spring which serves the spur leaves for spur fruit, but for any fruit I’ve heard about the number of cells is determined in spring and early N helps quick development of leaves that serve the fruit. Late summer to early fall (post harvest) apps of quick release can accomplish the same thing- especially with apples. Some growers do both and some growers use foliar N in spring. Slow release organic N is not a bonus for fruit growers because delivery to the trees occurs at highest rates in summer when it serves vegetative wood not related to fruit production and often detrimental to it.

I have not found any specific research that identifies the precise time water deprivation leads to higher brix and FN can’t do that research either- obviously, those of us in the humid region can only compare wet to dry years and this one is wet. I’m still harvesting barely edible but absolutely beautiful peaches. Nectarines have been fine up until now, but the first Summer Beauts have been bland. Hope they start getting up the brix because it is my biggest nect tree.


I believe water deprivation is misunderstood by the general public. The quantity of deprivation is highly dependent on climate and soil. Commercial farmers I’m aware of who practice this (esp. grapes and pit fruits) have automated systems monitoring soil moisture at multiple depths. It’s really about avoiding overwatering which can effect both fruit quality and your water bill.

I think most everyone agrees that thinning is important with pit fruits – not just for fruit size but health of the tree. In addition, R.S. Martin’s advice that you head back whips during dormancy is also important. See the pamphlet for details.

With regard to “which fertilizer” I think this is a poor (sorry) question. The research I’ve read argues that for deciduous fruits: the ratios of available nitrogen, phosphate, and potash in the soil at depth (not surface) one month before leaf fall begins should ideally be 2:1:3. In particular, the roots cannot manufacture the precursers to sugars without significant potash. However, uptake of available potash is limited by other nutrients – especially available nitrogen. This is why the ratios are 2:3 for nitrogen to potash. Now as for quantity of fertilizer, this is again dependent on local climate and soils. Note also that excess potash can be toxic to plants.


You should reread that post. Fruitgrower said it stopped raining in early April and turned hot and windy. His June Pride came off in late June as I recall. That’s 2.5 months with little rain or irrigation and lots of 100+F weather. If you had 2.5 months like that in NY I think you’d call it dry, forest fire dry. Which by the way is exactly what happened near him in CA starting in June.

But then again this question is about fertilizer not water. I just keep my trees green and thin for size. Works for me.



I’ll comment on peaches. I know you asked specifically about fertilization, but as mentioned there are many other factors which affect peach size.

I remember seeing pics of your orchard and it’s stunning well kept appearance. But around here I see size suffer significantly because people allow sod to grow too close to the trees. Peach trees compete very poorly with sod, with small fruit being one of the symptoms to show up.

I think this could also be true in higher density plantings (I think I recall your orchard may be fairly dense). The article I’ll link in a moment talks about a decrease in fruit size with an increase in density.

One big big factor is the maturity of the peach tree. Almost no one talks about this in the industry or research papers, but it is a very significant issue. I have seen this over and over, since I graft a lot of my own trees. I have mature peach trees along with younger peach trees of the same variety, and there is generally fairly stark difference, although it seems to vary with variety.

This year I harvested Redhavens off of mature trees along with a half a row of younger Redhavens. The younger Redhavens produced much smaller fruit over all. Glengo produces a little more consistent fruit, but still definite size difference in the age of the tree.

I don’t think most people would notice this because as their trees grow in maturity, they forget the average fruit size they picked when the trees were younger. I know this was the case when I just had a backyard orchard. I never really noticed the fruit size increasing as the trees matured.

I agree with Alan that early fertilization (or perhaps late fall the prior season) is going to add the most to peach fruit size. How this affects brix, I have no idea. My gut feeling is that early fertilization would not harm brix, and could perhaps improve brix due to more leaf tissue to “feed” the fruits.

I know we’ve talked about this a million times on the forum, but I think someone once posted some research which indicated N improved brix, as long as there wasn’t so much N that actually shaded the shoots with fruit on them.

That said, I would use the amount of shoot extension (i.e. vigor) as a gauge for how much N. I have some mature trees which didn’t put on enough shoot extension and should have been fertilized. Others, we’ve pruned twice this growing season to keep light coming in the tree (i.e. too much vigor).

Of course variety is a big deal. Some varieties are smaller and will “punish” you much harder if you leave too much fruit. Others don’t care how much fruit you leave, the peaches will still get huge (However, even these varieties will punish you by breaking off their scaffolds and/or secondaries.)

This summer I had some crop adjusters out to the orchard to estimate our bu./ac for insurance purposes. They counted some mature Redhavens. I think the average number of fruit was in the low 200s per tree, but on Redhaven had over 350 fruit. On that Redhaven, although some of the fruit was big, a lot of the fruit didn’t size as well as I’d liked.

Compare that to Baby Crawford. That tree probably also had 350 or more fruit on the same sized tree. I’ve picked at least 175 lbs. off that one tree, and there is still fruit on it. The fruit was all very uniform in size, and almost all large.

Small sized varieties like Harken can size fruit, but they have to be thinned hard and early.

I’ve posted this before, but here is an article on how to grow big peaches.


… when it is increasing the plant’s access or processing of available potash.

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Just a thought, fertilized trees in my orchard attract deer. They will eat all leaves on young plants, all summer. I will thin fruit for size until trees are large, tall enough that deer damage will not matter.

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What’s the size (dimensions) of your orchard?

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My main orchard is 150’ by 240’.


If I were to build a 14’ high perimeter fence for those dimensions here in California using 4’ deep cement post holes, galvanized steel polls and chain link fence – the cost would be about $12K for materials plus my own labor and renting an auger for a day.