No, different flowering times, let alone any anti-selfing mechanisms that may be present in either species. No such cross possible. Your N. maple was pollinated by wind-blown pollen from another N. maple, "somewhere". They're ultra common.

+oM

Despite their superficial similiarities, Sugar Maple and Norway maple aren't all that closely related within the genus. The closest relatives to Norway Maple, IIRC, are Acer truncatum and Acer mono.

Sugars can only cross with other species in the same group, like Acer grandidentatum, Acer leucoderme, and a few others.

any idea how far pollen blows?

Pollen can not only blow for several hundred meters or more depending on wind conditions, but it can attach to flying insects.

Wind-blown pollen is tiny, compared to that moved around by insects. Hence its ability to travel some distance, and to end up in the lungs and breathing tubes of miserable humans far and wide. I don't know if airborne pollen is ever carried by insects, but that's definitely not the main event. But yes, considerable distances...I'd have to really drill down to see what research has shown with regard to outside parameters, but I bet it would be astonishing. I would guess there's pollen of a wide assortment of wind-pollinated plant species floating around at some level of the atmosphere most of the time and in most of the places one would look.

+oM

But maples should have insect dispersed pollen, not wind dispersed

Can't say I agree with you there, Hug. Maples, and indeed, most tree types are wind-pollinated. This factoid helps explain why certain persons are bothered by pollen very, very early in the growing season, as trees do tend to flower very early. Not all types, of course, but going back to maples...silver and red (and of course, Freeman) maples all flower in March most years up here, and that's still "winter" in terms of the weather most years. But it is wind, not insects, which move this pollen around, and it is therefore very tiny pollen. Insect-pollinated plants have pollen that is huge in comparison to wind-pollinated types.

+oM

But norway maple flower much later, at least here. It flowers just before the leaves emerge, probably in the second half of april. The flowers are full of nectar, people used to eat them as candy in old days. You can even hear a norway maple twenty yards away in spring because it's so full of bumblebees and other insects. It's very possible that this differs among the species of maple though.

I do agree that bees can indeed be attracted to "hard" maple flowers. It's just not the primary mode of pollen transfer. But you're definitely right that bees can and do sometimes frequent these trees while in flower.

+oM

Unlike Sugar maple, with its small-petaled, close-mouthed flowers on dangling stalks typical of wind-pollinated maple species Norway maple produces an out-facing, comparatively close bunch of conspicuous flowers which normally sized petals, that open wide to accommodate insect visitors.

Pollination: by wind or insect?

https://blogs.reading.ac.uk/whiteknightsbiodiversity/2014/04/06/pollination-by-wind-or-insect/

I think if you do the research, you will find that the vast majority of maple species are indeed insect pollinated. The genus tends to be a bit of a generalist, and hedging its bets, can also benefit from wind pollination, but it is by no means necessarily the principle vehicle for dispersing pollen. These trees are all heavy nectar producers and nectar production (as well as scented flowers) is a biological adaptation intended to attract pollinating insects. The primary exception is box elder, Acer negundo, which is exclusively wind pollinated and does not produce nectar bearing flowers.

I think Acer rubrum and Acer saccharinum can go both ways. It blooms so early (anywhere from mid-Feb to early April here) there often aren't many bees and other insects around, but I have seen them working rubrum and saccharinum flowers on warmer days.

Various researchers and authors

have wrongfully reported that sugar

maple pollination is done solely

by insects - technically called

entomophily. However, a few

have mentioned the possibility of

pollination by wind - anemophily,

or mixed pollination i.e. by both -

ambophily.

Clues as to the pollination

mechanisms can be seen in the

floral structures. If the flowers are

small, greenish and dangle in the

wind - such as in Manitoba maple

(Acer negundo)

- wind pollination

can be inferred. If the flowers are

larger, perhaps more colourful,

and are held closer to the twigs on

which they are borne - such as in

striped maple

(A. pensylvanicum)

or mountain maple

(A. spicatum)

- then entomophily or ambophily

can be suggested.

http://www.researchgate.net/publication/272562811_Pollination_and_reproduction_in_sugar_maple_trees

Well, I learned a bitty bit here, but as was said above, when silver and rubrum maples flower here, there are virtually no insects present. I really do mean none. Most typically, this is a time of snowbanks, ice in the roads, etc. Not the flowery time of spring as it's usually considered. Plus, maple pollen is considered a primary allergen, and that is near-always going to be a wind-pollinated plant bearing numerous, though tiny, grains of pollen. That point was alluded to in the link Embo provided, the tininess and prodigious production of maple pollen. I'm wondering if they got that right. I can walk with my fingers right now to other web sources that state, categorically, that maples are wind-pollinated. I'll tell you what...I'll be watching for this going forward. I said I learned something, but obviously, I don't totally believe it at this point. Again, these trees flower long before any insects are around.

+oM

Oh, Look:

http://www.researchgate.net/publication/272562811_Pollination_and_reproduction_in_sugar_maple_trees

I think we all learned something here today, at least I did. But, to return to the original question, would a pollinating insect fly a kilometer between two trees? I think so, at least in spring when there might be far between nectar sources. Wind blowing in the right direction will help. The fact that there was only a dozen filled seeds suggest that the pollination was not very good, wich might indicate that the distance was almost to much.

As far as I know, it is only "bumblebees"...do you have that term in Sweden?-that are active in the earliest going. For example, I just planted some honeyberry bushes up at my land. This very-early-blooming honeysuckle type is insect-pollinated. But because it blooms so crazy early, it is really only bumblebees that do the work. Luckily, my land is full of wild flowers, differing habitat types, water, forests, etc...so plenty of bee habitat. As to how far a single bee will fly to go from plant to plant, that varies by species too, of course. I'd have to look it up to really break that down. But again, for these very early-spring events, we're really only ever talking about bumblebees. And I'm not certain at all that they have a thing to do with maple tree pollination. In fact, I strongly doubt it.

+oM

Bumblebees will be most common at the time a norway maple flowers, but I think many ordinary bees will be active as well.

Can't deny that photo! It may be that for N. maple in particular, the insect-pollination strategy is a bigger item than for other maple types. I'm about as sure as a guy can be that when the big silvers and reds are flowering in what is in reality, still winter conditions, there are no insects involved. And that paper I linked up suggests the same is true of sugar maples.

+oM

I totally agree with you about red, silver and sugar maple, if they flower that early they have to be wind pollinated. The Norway maple is in another subgenus however, and they seem to be insect pollinated or both insect and wind. It would be interesting to know what the characteristics for the platanoidea subgenus is, maybe insect pollination is a part of it

Silver maples definitely attract honeybees, if it's warm enough. Usually there's some days even in March when they can work.

Which brings up a question, if my Chinese elm is wind-pollinated, why is it swarming w/honeybees when in bloom (in fall)?

I'd argue that most maples are at least capable of being pollinated both ways. Sugar Maple flowers, however, look almost more like oak flowers than other maples, the way they dangle. But they bloom well into April here most years, and bees are buzzing around pretty actively by then.

Right. As someone up yonder alreadymentioned, even though we often tend to think of Norway maple as Europe's version of, or should I say, Europe's occupier of similar niche-to our sugar maple, they are not even really all that closely related. One look at that white sap ought to tell you that, but I never really thought about it for years.

I'm wondering...I must have related the story on these pages of the big stream restoration project with the gypo Illinois contractor that tried to pass off Norway maples as sugar maples?!? What a crock that all was. They sucked in so many ways, but above all, I cringe at the thought of how many projects they've had where there was nobody on hand to inspect the plant material as it arrived at the site. They actually had the nerve to argue with me about it! I did the petiole thing with the sap, which is just plain conclusive. So, still trying to not take these stupid trees back to Chicago, a mere 200 miles south of us-they then said that that nursery told them the trees looked like N. maples "because they were cultivars"!!! As if that-even if true-would have made one bit of difference. We don't tend to use cultivars-not even "nativars"-in these types of projects. Of course, I was not impressed with any aspect of that company, which name shall not be written here. But they truly were clowns.

Meanwhile, that woods and every other woods in this region is packed with sugar maple seedlings at the ground layer. But here, because this is in town, Norway maple seedlings abound also. The good news there is that nature always produces far more offspring than will ever survive to adulthood. That was a funny, if frustrating summer, when those guys were up here working. The gal who was put in charge-this after the original foreman got fired mid-project-was herself a piece of work. One of the understory plants called for in the plans was our native chokecherry. Well, "*arcy" kept saying 'chokeberry', itself a fine native plant, and I kept saying "now *arcy, chokeberry is a nice plant, but this plan calls for chokecherry. Well, you know how this turned out, right? A day or two later, there sat a semi trailer loaded with plants, amongst which were several hundred chokeberries! She wasn't the type to listen! Luckily, the DNR guy who had the last word was okay with the Aronias. Just an indication of what this particular contractor was like to work with.

+oM

(BTW, many more flying insects than bees)

Good point Dan, many kinds of pollinators besides bees.

Bees apparently visit maple flowers often enough to sometimes produce maple honey: http://www.honeybeesuite.com/what-about-the-other-125-species-of-maple/ ... this link includes a photo of a honeybee on a red maple flower.

But back to the OP's question - what do the Acer experts out there say - is it possible for Norway and sugar maples to hybridize? A google search yields a couple obscure references that seem to indicate it may be at least theoretically possible.

So a maple can't produce fertile seed by it self? This fall I collected seeds from a bigleaf maple, acer macrophyllum. They were clearly filled up, but there is no other tree of this species around. The big leaf maple is a tree that is very rarely grown around here, this particular tree is actually the only one I have ever seen in person. However there are probably about a hundred other species of maple in the vicinity since it's a botanical garden. Any of those could be the father, but it appears that acer macrophyllum does not have any close relatives. It's in a subgenus of a subgenus of acer. How closely related do they have to be to cross?

Location seems to matter in this debate. I would hazard a guess that no maples are insect pollinated where I happen to live. Something happening in say, Maryland, or what have you...may have little to no bearing on our situation. And the mere presence of insects buzzing around a tree that happens to be in flower does not constitute proof of insect pollination being that tree's main process.

As it is, I think some of the references already linked up here point to the "fact" that while some insect pollination may go on in Acer, it's not the main show.

+oM

It might be worth putting large square screen bags on a maple, ones big enough to exclude bugs but not windblown pollen. I might go get a branch off a second norway maple and graft it in the spring. It would be a few years till it bloomed, but I'd have an answer to curiosity. I could even put a blooming branch in a bottle of water and tie it into my tree and see if bagging it allows bugs to pollinate mine. No bugs inside the bag and filled seeds means wind is OK. No bugs and no seed means bugs are needed?

This document lists the intersectional hybrid platanoides x saccharum (p. 8):

http://www.maplesociety.org/sites/default/files/SymposiumBelgium2011/Acerhybrids-PietDeJong.pdf

wow, arbordave, so it seems there is one obscure reference from 1953 of the very item hug is wondering about, a platanoides/saccharum hybrid! Most unexpected to me, but then it is just a single, unsupported factoid on this listing.

+om

"So a maple can't produce fertile seed by it self?"

Some can.....some can't. I would be very hesitant to make generalizations about the pollination/fertilization of Acer species - their sex life can be extremely convoluted.

Bigleaf maple, Acer macrophyllum, is heterdichogamous. It's a rather rare mating system but functions much the same as a monoecious process does so selfing is quite common with this species. Acer rubrum is even more convoluted in its reproduction process - they are considered to be polygamodioecious, or able to produce either male or female flowers; or produce both male andfemale
flowers; or can produce flowers where both male and female parts are
functional. And these traits can change during the course of the life of the tree.

And it goes on - Acer negundo is dioecious (so no selfing) Acer saccharum is monoecious (selfing possible) and Acer palmatum is andromonoecious (selfing possible). And depending on source, Norway maples are either dioecious or monoecious (or maybe both), so who knows.

Gal, just trying to understand...so are you equating a species being monoecious with its being capable of selfing? While both traits can certainly coincide, I do not think it true that one automatically allows for the other. in fact-just looking at the pineaceae-most are monoecious yet most also have anit-selfing mechanisms in place-I think.

+oM

Notice at the above link that assumed hybrids with guessed at parentages as well as presumed hybrids where no determination of parentage is indicated are mentioned - without more information the Norway and Sugar hybrid published by Wright may have been unconfirmed also. Nowadays, if somebody wants to take the time and trouble, has money to spend on it such guesses can be investigated at the genetic level. Otherwise parentage assignments for plants not resulting from intentional breeding programs with documentation are based only on how the plants look on the outside.

Tom, as I stated, generalizations are risky :-) Being monoecious is certainly no guarantee of selfing but it does allow the possibility, provided self-incompatibility is not present.

Righto-we're on the same page then. Embo, I would think an investigation of ploidy levels would rule out...or in, as the case may be...the possibility of such hybridization being able to happen. I'm not sufficiently freed up here today to drill down that deep, but basically-if I'm not mistaken-a diploid plant cannot interbreed with a tetraploid, etc......again, if that is not a misconstrued attempt on my part to understand. I don't think it can happen when such is not matched between species.

+oM

If it helps any norway maple and sugar maple are both N=13, or 2N=26 species. Any more than that, I don't know. So, assuming my seeds come up in the spring, how would I know the difference between pure platanoides and hybrids with saccarum? The wind direction for the two trees at the corner of our road was good at pollination time, so those two norways can't be ruled out. The norway I have is red leafed, Royality, so anybody know how that trait is inherited? I'd love a red leafed sugar maple backcross...grin

Embothrium - one thing I noticed on p. 8 of that link, a couple of the hybrids are called "unlikely", but the platanoides x saccharum is not called "unlikely". I'm no maple expert, just wondering if the hybrid is actually possible (not likely in nature, but perhaps thru intentional crossing)?

I think the most we can make of that is that somebody, at some time, considered this cross to be "possible". There are no citations, no references, just one obscure reference. That's not much to hang your hat on.

+oM

The author - Wright, as I remember it - and date of publication are given after the parentage of the Norway, Sugar cross. But no name for the cross, as in Acer x freemanii so apparently nobody took it that far. (Other crosses that have even become commercially prevalent appear to have never been given their own names also, for instance the Norway, Shantung hybrids being made by Keith Warren at J Frank Schmidt).

found Wright's paper from 1953:

http://www.nrs.fs.fed.us/pubs/sp/sp_ne056.pdf

Page 16 (13) says, "... hybridity certain. Seeds were set in 11 out of 34 crosses; most of seeds were very poorly developed, but did contain an embryo. The few seeds that germinated were of nearly normal size ... The seedlings obtained resembled straight A. platanoides, but are slightly smaller and darker green."

So (based on your excerpt) it sounds like it was an artificial hybrid resulting from controlled pollination, and may never have been known to occur spontaneously.

I would agree with your conclusion - a natural platanoides x saccharum hybrid seems pretty unlikely.

However, in "Introduction to Forest Genetics" by Wright (1976), p. 334 states "Of the 16 natural and artificial hybrid combinations which have been reported (Rehder 1940, Wright 1953), 11 belong to species belonging to the same section. ... Each of the 5 intersectional crosses was reported as a single natural hybrid that occurred in an arboretum where different species were grown together."

I guess I'd have to get the 1940 Rehder book (Manual of Cultivated Trees and Shrubs Hardy in North America) to find out what the 5 natural intersectional hybrids were; is it possible that platanoides x saccharum was one of the 5?

Only The Shadow knows.

Speaking of Norway maples -- right now they are turning yellow, later than most trees & so quite visible where they occur. Quite surprised how they've invaded many areas in my mountainous area & capable of growing in the shaded forest understory like sugar maple.

Yes, highly shade-tolerant. So back to that possibility of hybridization...since I like the sugar maple just the way it is...and since this cross does appear to at least be possible, one wonders if the very proliferation of A. platanoides into the wild here in N. America might not increase the opportunity for this to happen.

+oM

Maybe a year with a very cold spring that suddenly turns over and become warm. That might delay the flowering of sugar maple enough to meet the normally later flowering of norway maple.

We had a very late spring here, PEI, after a heavy snow winter. Norways and Sugars bloom overlapped. Norway started sooner but had not finished when the Sugar maple started. The sugar maple is pretty tall, so I did not closely examine the blooms to see what stage they were at.

Sorry folks, I got the bloom order on my two trees backwards. Oops.

That's interesting. Well, seedfall in Sept or so will tell me if both or either tree made any filled seeds this year. I grew out some of the Norway samaras, getting what looked like pure platanoides. Since I din't want a bunch of those, I composted them. The sugar maple dropped some blank samaras this summer already, but it's pretty tall....meaning I will have to wait for seedfall to see if any filled seeds happened.