Graft healing temps - burning the midnight oil

Hi! Considering trees that require higher temperatures for graft healing, like persimmons, does it matter if I graft at night? This will result in the early hours following the graft being lower than ideal graft healing temps. Conversely, is grafting in the morning best for this reason?
I may be splitting hairs here, but I may be grafting a bunch at odd times, stolen from the early, or late, hours of the day. And if it’s beneficial to do one over the other, well, that’s worth knowing.

I haven’t done that much grafting, but I’ll venture a guess most folks don’t graft at night primarily due to inability to see.

If your overall temperatures permit the rootstock to push out growth, I think you’d be okay regardless if you graft at day or night. After plants wake up, it doesn’t decide to stop growing because it’s a little chilly. It has to keep going…even if it’s a gamble the weather decides to go sub-zero.

Hi Aaron,
If your ambient daily highs are near these optimum values, you should be able to do grafting anytime of the day.
Kent, wa
Many people ask what are optimum callusing temperatures to ensure a good percentage of viable grafts.

Nectarines/Peaches – 18-26 deg C. ( 64.4 to 78.8F)

Apricots/Cherries – 20 deg C. ( 68F)

Plums – 16 deg C. ( 60.8 F)

Apples/Pears – 13-18 deg C. ( 55.4 to 64.4F)

Walnuts – 27 deg C. (80.6 F)

Grapes – 21-24 deg C. ( 69.8 to 75.2 F).

Figs - 23.9- 29.4 deg C. ( 75-85 F).

Do not forget tissue damage for most temperate fruit will occur at temperatures over 30 deg C. (86 F)

Temperatures either side of the optimum will also work, but the percentage take will be reduced. See graph below for walnuts.



Callus graph showing optimal temperature range


Great info. Do you also happen to know grafting temp for persimmons, loquat, or almonds? Almonds are my new project …ever since I ate a great 'Reliance" almond grown at Mt. Vernon Research Station.

I wonder if you were able to graft those peach scions. Temp range 64-78 is not till mid July here. By that time the scions probably would have budded out in refer!

Last week worked on your plum scions. Didn’t know temp range but, I see thankfully it’s close.

Hi Chris,
I have not seen a published temp for callousing persimmons, loquat, or almonds. But a number of members with experience in persimmons recommend we wait until the ambient temps are in the 70s on a steady and reliable basis. So I always wait until after I do persimmons to graft my peaches. I am still waiting on both persimmon and peach grafting.
I have had good persimmon results when temps are above 70F, and trees are growing vigorously, usually leaves about size of a rabbits ear.
Loquats and almonds, I do not know about, but I am intrigued about your almond comment. I had always thought you need CA climate for almonds, so I would like to know more about how Mt Vernon is growing this one!

This spring was a very strange one for peaches here, I had blooms galore with virtually no resulting fruit! So I will be grafting more peaches soon, but if next spring is like this one, I may need to forget about peaches. I have no idea why no peaches could set fruit since the weather here was unusually warm and seemed perfect for pollination.
Did you have similar experience?

“Almonds are my new project …ever since I ate a great 'Reliance" almond grown at Mt. Vernon Research Station.

Is there any benefit to grafting on the south side of a tree where the sun warms the graft for trees that require higher temperatures for callousing (hickory/walnut)?

Went out to check peaches and something similar … there had been lots of bloom but now only about 15% of normal set. Last year trees were loaded - maybe I should have thinned more or maybe it’s weather related.

Curiously, I have Harcot and Hardired nectarines grown under partial overhead and side cover that are loaded with fruit. I had lights and heat tape on them over the really cold winter period but had taken everything down once I saw flowers … so a few too many variables to compare the peaches and nectarines.

We’ve had some cold mornings in last month (30-31) and maybe that’s the culprit. The overhead cover on the nectarines might have kept them a touch warmer than the peaches. Not sure.

As for almonds I’m trialing 'All in One", ‘Nikita’s Pride’, ‘Prima’, ‘Javid’s Iranian’, and some scions I ordered. The 6 year-old 'Reliable" variety at the Mt. Vernon Research Station is out in the open and had almonds on it last August. They were the hard shell type and it took blows with a hammer to crack open. It tasted great, like almond extract, but I decided to mostly go with the soft shell types for ease of harvesting.

There will be the same problems with almonds as with peaches, i.e. peach leaf curl and early bloom. But after the usual routine of alternating copper with lime/sulfur, I tried out ziram this year at bud swell. Wow, no curl! Now I’m more inclined to take a chance with almonds.

Only here the squirrels greatly outnumber us so I think almonds are not a way for us to go, but wish you good luck. I am surprised that the climate here is warm enough. If my peaches fail another year I will just grafte them over with plums which always seem to do well here.

Hi Chris,
I’m about 100% sure I have PLC on two of my new trees even though I sprayed them several times last fall and several times pre bud break. Here are pic of today. What have you done in past when you noticed an infection after bud break? I have read that there is no effective treatment after leaves are infected. Please advise


Looks like PLC in pictures 1 + 2. After at least 10 years of spraying peaches with LS and Kocide (alternated monthly from Nov-Mar) and still getting 10-15% curl, I gave up on organic controls and, at the last minute, went for Ziram.
@jsteph00921 was willing to let me buy a little bit and I tried it out on March 3. Buds were already at green tip and I thought it might be too late. Great results- no curl at all on any of my peach trees! Even though this was not a controlled trial, after years of only partial success with LS and Kocide, I’ll be switching to a fall and spring spray of Ziram.
Yes, no treatment after leaves have curled. But you don’t have a bad case. Even if you pick off affected leaves, tree recovers with more.

Thanks Chris,
Looks like I will pick off leaves and burn them.
Do need to prune off wood than appears dead? Will need to find your product Ziram this fall.
My plums did benefit so far, I have some minor curl on Sweet Treat Pluery,

So it worked for you. That’s great to hear.

Yes, thanks for your generosity! I’m sold on Ziram - maybe only need a fall and spring spray.

Here near Houston always wait until rootstock leafs out for persimmon but before temps in the 90s. Are leafed out now and daytime in the high 70s to mid 80s. Have some bark grafts and whip/tongue already pushing.


Continuing the discussion from Graft healing temps - burning the midnight oil:

This is @scottfsmith’s guide from March 2020. Great details!

"There have been many threads here on when to graft, but one thing I would like is a list based on how far along the leaves/buds are on the stock. The temperatures are also important but that information is more well-known; I’ll include it here anyway (highs for the day are what is listed). Note that temps are callus temps and do not take into account the fact that the sun may be warming up the graft unions well beyond these ranges. The sun can add 20F to the air temperature and will significantly change the rate of callus. Also remember that grafts also will callus at night, it is having as many hours as possible in the ideal callus window that matters.

Anyway here is my current thought… I will edit this based on comments. These timings are not uniform across all climates unfortunately, but hopefully close enough that we can share data."

  • Apples - 45-70F. Tight cluster is optimal, up to 1" leaves still excellent. You want to graft apples on the early side compared to most things as there is a big spring flush of growth that early grafts will get and late grafts will miss. There is a fairly wide window of opportunity, but don’t graft before major bud swell and don’t bother once it is hot.
  • Pear - similar to apples and generally easier to get takes so more leeway.
  • Peach - 65F-80F. 1-2" leaves seems to be the point when I have had the best luck on average over the years. 1/2" to 3" can work depending on how the temperatures are, peaches are more grafted based on temps than on growth because they are so temperature-sensitive for callusing. The above range is the callus window but don’t forget the sun effects, and shield with aluminum foil if it is getting sunny and temps are in the 70’s or higher.
  • Apricot - 60F-80F. Similar to peach, also almost as difficult.
  • Cherry - 55F-70F. I am a bit rusty having not grafted cherries in a few years. I think it was 1/2"-2"?
  • J Plum - 55F-70F. Graft at 1/2"-2" I would say; they are easier than peaches but harder than E plums.
  • E Plum - 55F-65F. 1/2"-2". Similar to J plums but easier to get takes.
  • Grape - 80-90F. Around 6" of growth is needed before it is warm enough to graft grapes. Or wait til 1’ or so and graft to the base of the new green shoot. I have had best luck with this approach and do all my grapes this way now.
  • Kiwi - 60-70F. 1-2" leaves. They seem to do better on the early as opposed to later side, the plants accept grafts more willingly when not too late.
  • Persimmon - 70-80F. Persimmons bud out relatively later; I would guess my leaves are usually around 1/2"-1" long when the temps have warmed up enough to graft. The ideal window is a bit hard to hit as you want it to be warm but when the plant gets too far along grafts seem to be rejected. If the buds are small the bark may not be slipping yet, persimmons are a bit delayed on getting the bark slipping compared to other trees.
  • Pawpaw - 55-75F? Pawpaws are usually pretty easy as long as you are not really late… 1"-3" leaves should work.
  • Jujube - 60-80F. Jujubes should have little nubby growth of at least 1/4".
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Well I’m happy to help. Anytime

What’s the difference between J and E plums?

(Scrolling is slow but gives you time to contemplate!)