Hickory pollination

I have questions that i couldn’t answer via searches: there is an awesome pecal pollinaton chart thread and lots of info on hazelnut pollination but very little on hickories which along with most nuts can be picky pollinators.

Question1: can shellbark and shagbarks pollinate eachother or is this unlikely (due to pollen compatibility, bloom timing etc) could also ask the same of pecans pollinating other hickories (i know there are hicans but im talking in terms of making a tree have a full crop)

Question2: do hickories express pollen allenes like hazelnut or is it simply a matter of having bloom (male pollen from one variety at same time as female bloom from another or even same variety).

Feel free to add insight if i’m missing some other important facet of hickory pollination and i look forward to the answers!

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They each bloom at different times: pecans or hicans, or hickories. You will always need (2) of the same species to get adequate pollen. And the answer to your question about pollination among species… is all can pollinate each other, however, bloom overlap doesn’t happen very often, or hardly ever.

So, you need (2) of each to gain adequate pollination. (2) pecans for pollination; (2) hicans for pollination, (2) shagbarks for pollination, (2) shellbark for pollination. Those are the main eating ones but other species of hickory are edible and they likely would need a mate of their own-species, as-well.


@Barkslip thanks for the reply. I get that you need two for each species but not any two will do (there are early and late pollen releasers correct?..cant find this info for hickories).

So your sayings its all about timing unlike hazelnuts where its timing and gene compatability. Which is where my cross species pollination (ie shellbark pollinating shagbark) came in if the blooms were close enough to help pollinate (for example if my two shagbarks only gave good pollination to one variety could a shellback potentially help pickup the slack).


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Right. And people who have been at hickories/hicans/pecans know that pecans are completely different.

However, (we) also know that any (2) shags or any (2) shellbark, or any (2) hican will always pollinate the other mate of its’ species. That’s why you’re not finding the information. It’s not necessary to know.

I have stood and witnessed myself when hicans and shagbarks and shellbarks and pecans were in flower and not a one of them overlaps. I’ve seen it with my own eyes and two older gentlemen have seen it for 40-years. They’ll tell you the same answer. Cheers, Carlin.


Thanks for the clarification, sometimes the lack of an answer is an obvious answer!

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I will suggest asking …
Ernie Grimo, the owner of Grimo Nut Nursery,
Due to the unsettled genetics of the hickories, this could be very complex.

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It’s the opposite of complex. Sorry, but, why waste somebody’s time when the answer is glaring at you.

I wonder how much time I waste.


Well. …?
There are many in the genus “Carya “
Some ? “ Species…? “ .,of which cross .
Many cultivated ,and wild hybrids.
The true identity of a individual , may be uncertain.
Genetically very heterogeneous.
So I think to say One will cross with another or not , is uncertain.
I do agree that bothering a nursery man at this time of year is bad timing , but if was to think of a individual that would know, I would ask Ernie G. And or his daughter Linda

So you don’t know is what you’re saying, correct? And you think I may not, that’s also correct, right?

Yes, correct

And why wouldn’t I know?

You met my best friend who spent more than 30-years evaluating pecans, shellbarks, shagbarks, & hicans in the wild. His friend also spent that time with him. And occasionally, Grimo and John Gordon would come along with Gary Fernald and Bill Totten.

And so I stood there with two men in their 70’s and 80’s pointing at the staminite and pistillate flowers of a mix of hicans, hickories and pecans and they explained it all to me and showed me why… yet you still have doubts.

Then, I have Fred Blankenship telling me the same. He’s only 80, too. Only been doing this 40-50 years.

You might recommend someone other than any of these men to @Carlin since you doubt me. I mean I got my information right from them. So, me, Fred Blankenship, Bill Totten, Gary Fernald, Ernie Grimo, & John Gordon never got it right, you’re still going to say…?

This is child’s play, Dave.
hope you saw my message this morning.


Dax, I have to modestly disagree with your position. Hickories as a genus all demonstrate dichogamy which means that male and female flowers are separate but on the same plant. Dichogamy is triggered by phytochrome signalling inside the plant - a fancy way of saying that temperature and light exposure are the triggers for buds to break and flowers to open. Dichogamy in pecan is far more diverse than in any of the other hickory species I’ve looked at. By this, I mean that pecan trees produce pollen from April 1st to May 20th in my area. The other hickory species I’ve looked at (shagbark, shellbark, mockernut, myristiciformis, glabra, aquatica, and bitternut) all have highly specific bloom periods lasting about 3 weeks where pecan is busy pollinating in a 7 week interval. Shagbark and Shellbark overlap each other to some extent.

All of the hickories need pollination partners with a protandrous variety paired with a compatible protogynous variety. This is partially mitigated by the relatively narrow bloom period of most hickory species. As OP noted, we don’t have pollen compatibility information with the hickories. I hesitate to give anyone pollen partner recommendations for any species other than pecan. What I can agree with is that planting 3 or 4 shagbark trees should give pretty good pollination and would make a similar statement about the other species. This presumes 4 trees each of a different variety.

It is worth taking a minute to look at the chromosome number of hickory species. I think most of them are in wiki articles linked on this page. Hickory - Wikipedia This is important because species with the same chromosome number are more likely to cross than species that have different chromosome numbers. Also, species in the Apocarya group are much more likely to cross with pecan and vice versa. A special case exists for Carya Myristiciformis (nutmeg hickory) which sits intermediate between the carya and apocarya groups. Nutmeg hickory often overlaps pollen shed with pecans.


beautiful stuff there Darrel. Properly written. As I mislead everyone but not on purpose, I wish I had written that (3) cultivars of the same species (or as you say there is at times some overlap among shag and shellbark hickories). I say this now because it occurred to me after I had written what I had that John Nolin always recommended (3) of something. That is, (3) of each species of grafted cultivars if you’re looking for grafted nuts, which you should be looking at. Seedlings will have their position in other formats, but feeding families, it’s grafted-cultivars.

I didn’t mean to chase you David, but, I did. You were right.

Darrel I appreciate the chromosome reference which I will get a chance to look at, later.

All the best people.

Thank you.



cheers … Dave, hope - yer cider has lasted thru the year. I have to report my friend, to you, that I have a very-special— keg of hard cider being delivered, Wed. , two days before, my surgery. More to always … follow,

thank you, for, the advice-today,


Thanks for all the insight everyone was just curious i have 2 shagbarks and 2 shellbarks coming from grimos so will let everyone know in a decade or so when they (hopefully) start bearing (up here at 54deg north latitude!) I may try and add another scion or two once they get going to hedge my pollination bets…would have liked to plant more but on my 1/3 acre lot theres no more room (was pushing as it is!) Happy easter to all and thanks for the various inputs and suggestions!

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To add further confusion… there are differing size and shape pollen grains among the Carya species, with some influence in size based on ploidy level. This disparity in size and shape doesn’t totally prevent cross-species pollenation, but it significantly diminishes the success of such, even beyond the previously discussed issues of bloom periods not necessarily coinciding, etc.


Great info here, I appreciate all the knowledge being saved from the older experts and continued evaluation to add to the breadth of knowledge. Best wishes on your surgery Dax, hope you are back up to speed quickly.