Morus nigra (black mulberry) from seed

All I can do is send you encouragement. Trust me, I really do want someone to succeed in this endeavor, simply because I think Morus nigra produces the tastiest fruit I have ever encountered, and it is my conviction that all black mulberries in the world under different names are one and only one aberrant clone. It would be a shame if it were to disappear because of a microbe or something. It would be great to have backup similar but slightly different clones.


The issues with nigra seedlings sure sounds like severe inbreeding depression. The process of evolving into a 22X polyploid may have involved a lot of inbreeding already. You may have to grow hundreds or thousands of seedlings to get one with okay vigor. It’s also possible that the rare good seedlings are due to apomixis and are also just clones.


Are there Morus nigra trees that are completely male? I know they could switch sex due to stress etc., but separate males would suggest they may not all be the same clone. If they are all females that produce a few male flowers, then seeds may typically be the result of selfing, which could also be the cause of inbreeding.


Perhaps some fungicide should be used to stop the damping-off.

I couldn’t find a good answer, but the profile on the Trees And Shrubs Online website has some really interesting tidbits on the historical record of the species, with this in the section on cultivation:


Pliny the Elder suggested Black Mulberry had been ‘neglected by the wit of man’ (Pliny 1945). He was referring to the almost complete lack of Black Mulberry varieties, despite millennia of cultivation, with differences essentially limited to the size of their fruit. Bean, too, commented that this is ‘a very unusual circumstance in a tree so long cultivated’ (Bean 1981). This phenomenon could be related to the species’ very large number (22) of duplicate sets of its 14 chromosomes (known as polyploidy), which may also be a factor in the occurrence of both dioecious and monoecious individuals – and even a capacity to change gender in maturity (Comai 2005).

Nevertheless it has long been popular for its fruits and latterly as a shade tree and an ornamental. Pliny the Younger wrote that he planted one in the garden of his villa in Laurentum, near Rome, in the 1st century AD. Black Mulberry was also a tree of choice for the English landscape gardeners Fanny Wilkinson and Gertrude Jekyll in the late 19th and early 20th centuries (Coles 2019). In modern Britain the two most common M. nigra cultivars are ‘Chelsea’ (also known as ‘King James’) and ‘Shakespeare’. Neither differs meaningfully from the type; both were named because the original trees were of great age and had historic associations, but it is a moot point whether this merits the use of cultivar names. There is no comparable tradition, for example, of naming ancient yews or oaks, and were such a fashion initiated it would soon muddle the cultural histories of these great trees with a glut of unnecessary and unhelpful names. Those few M. nigra cultivars that are said to differ (marginally) in fruit size or flavour probably do so on account of environmental factors in their place of origin, and not because of any inheritable characteristic.


I missed this reply (I was clicking send on my own reply around the same time), but I’m not sure it counts as damping off if it happens years later when the tree is 5+ feet tall. I’m not sure a fungicide is warranted unless the cause can be identified as fungal. There could be bacterial, nematode, viral, or nutrient/pH reasons that nigra seedlings tend to decline over time. And until we know better where @Mikatani grew the seedlings, it’s hard to draw a broadly applicable conclusion.

I assume @chriso was growing them in south FL? Florida in general can be a challenging place to grow anything with weak roots or picky soil requirements. Figs suffer from nematodes, and many other trees suffer from fungal diseases that aren’t a problem in California, for example. Soil in both FL and CA tends to be alkaline, often with high salt content in the soil itself or in irrigation water. Any of these things could cause sensitive species to struggle.

OK…I’ve grown thousands of pecan/walnut seedlings, but the mulberry thing will be a new one on me.
Anyone have a specific recommendation on a type of seed-starting medium for M.nigra seeds?

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After the initial soaking, I just put mine in the same potting mix I use for garden starts, but I would also love to hear suggestions about what medium would be best.

You’re absolutely correct about these points and I raised them in previous posts on the subject elsewhere in this forum

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The idea of ‘completely male’ vs ‘completely female’ doesn’t necessarily apply in this case. Consider that trees can be broadly either monoecious or dioecious. So already, the monoecious ones are violating this dichotomy. And even amongst the monoecious species/varieties, there are cases where the sexual expression is able to be switched, I.e. a ‘male’ tree is suddenly ‘female’. Lots of plants are structurally dioecious, but functionally monoecious, because for some strange reason, they retain the structures of a stamenate or pistillate flower but lack the actual FUNCTION of that part, I.e. stamenate flowers that don’t have anthers or pollen.

We tend to think of these things in reference to ourselves. We are diploid, and our sex is basically (perhaps with some exceptions) expressed based on a single locus, that is one pair of chromosomes. As we all learn in high school biology, there are two chromosomes- labeled ‘X’ and ‘Y’- and females are homozygous (having two X chromosomes, I.e. ‘XX’) while males are heterozygous (I.e. ‘XY)
The situation in most plants is quite different.

From the little bit of reading I’ve done to understand some of what’s going in sex expression of trees, it appears in most sex expression is based on two loci, rather than a single locus. If that plant is a diploid, there are 4 alleles and potentially 4 different combinations of alleles to consider. If we label these, W/X and Y/Z, the combinations would be WW/YY, WX/YY, WW/YZ, and WX/YZ. When you add polyploidy in to the equation, it gets potentially very confusing.

Doing a bit of armchair ‘post-graduate’ work here, I located this chart summarizing different types of allele pairing corresponding to sexual expression.

I’m at the edge of my ability to conceive of the specifics at this point, but it becomes somewhat more clear why it might be that we see such a range of sex expression in plants, especially polyploids. In many cases sexuality and expression of sex traits is, simply put, essentially non-binary.

There has to be (I would think) a deeper reason for spontaneous changes in expression of sex. I’d suppose there would have to be an epigenetic factor that ‘turns on’ and ‘turns off’ certain parts of the equation. I’d guess, too, that the syntax of recombination in extremely polyploid species might make for some really funny genetic outcomes.

While I agree with the overall premise of your post, I think @kiwinut is already aware of those issues and merely meant to ask whether any nigra cultivars are known that appear to be only male (as other types of mulberries are commonly known to be), or whether all known nigra specimens follow the pattern of “mostly female with occasional male flowers.” The point of the question is to investigate the validity of the theory that all nigra known to produce fruit in all the world are actually identical clones of one another.

This is a very good way to think of black mulberry, perhaps also persimmon. They simply are not one or the other. They are both. Just don’t start thinking of them as hermaphrodites. That too is wrong.

I agree that DNA tests could shed a lot of light on the genetics, however, decrypting a genome with 14 base chromosomes duplicated 22 times is going to be daunting.

Re seed starting media, use promix BX or MPX. Start a lot of seed in a single pot/container sowing very shallowly. Keep the media moist. Seedlings should emerge within 10 days. As they emerge, carefully pick them out and set them into cell trays filled with promix.

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There has to be something bizarre going on with Morus nigra, something anomalous, and it must bespeak something curious about its past. Polyploidy isn’t uncommon, but the conventional wisdom seems to point to diploidy being more stable, so the tendency is to revert to diploid over time. What then would cause such a severe case of polyploidy?

The idea of a single clone having such longevity is compelling for its implications about humans’ potential role. I’ve read, for example, that amongst populations of Apios americana, all individuals north of (roughly) the Mason/Dixon line are sterile triploids. How then, we might ask, did it become such a ubiquitous plant? Surely rodents would have played some part, but it’s hard to fathom it extending its range thousands of miles without the help of man. Surely the fact that it is such a good source of food would lend credence to that revelation. Similarly, I’ve noticed many a stand of sunchokes growing wild here in northern New England where the season is such that the flowers open only a couple of weeks before frost, never (to my knowledge) forming viable seed.

I’ve come across different versions of the idea described above. by Mikatani. If true, it would seem to rattle some of the basic underpinnings of our understanding about our role in the natural world and the history of our involvement. Similar enigmas are found elsewhere, such as in corn, which modeling has shown to be to have had an infinitesimally small chance of occurring at random.

As an interesting aside, I’ve come across (though I forget where) the notion that Morus rubra and Morus alba might represent a single species, and that this would account for their free hybridization. Though the taxonomy might be clear enough to us lay-people, among plant taxonomists there have been differing schools of thought, some tending to lump things together into broader groups and others to break things down into very small gradations. When you get into the nitty gritty of trickier genera, like Quercus, Salix, Amelanchier, and Crataegus, you find HUGE variations in numbers of species given by different taxonomists. Since they freely hybridize and since site and climate can alter phenotype dramatically in many cases, it’s not altogether clear where one species ends and another begins. N. America is the center of diversity for Crataegus, and I recall reading that the tally of species in N.America varies by as much as two orders of magnitude depending who you ask. Perhaps this is being worked out now with modern biotech (I tend to doubt it), but it really is kind of an earth shattering realization that a concept as simple as a species has yet to be meaningfully defined in a way that doesn’t involve a whole slew of exceptions.

Corn differs from teosinte by 5 changes in the genome. Three are single gene mutations, two are chromosome fragments. While I 100% agree that it could not have occurred naturally, I also 100% can see how humans shaped the genome by selection during about 9000 years it has been grown.

Re the concept of a species, we don’t know as much as we think we do.

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Some leaves of a mature Morus nigra tree in the province of Soria, Spain

A view of the tree. It was harshly pruned.

Some more trees in an abandoned village/hamlet nearby

While locally known, the species is considered rarer now than before as a fruit tree, like something old and traditional.

I want to take some cuttings. Tried once and I got callus tissue, but I kept them too humid and rot ensued


Maybe if you’re lucky you’ll get a male or hermaphrodite M. nigra which can pollinate other mulberries. M. nigra can produce offspring that still has fruit very much like M. nigra, but with a lower ploidy. I suspect if crossed with M. alba or M. rubra it might be a step towards more cold hardy M. nigra type trees.

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I have a male mulberry tree. Just don’t know what type it is since it was a wild seedling that grew in my yard. I have many varieties of mulberries so it must be from the fruits of one of them which might be a cross.

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I have read that people view M. nigra as not very cold hardy, but in Spain they are all around, from the subtropical areas of the Canary Islands to, for example, the trees I have shown in this thread, that grow in a an area that gets quite low temps in the winter (this winter they went to down - 14 Celsius, which is like 6.8 Farhenheit looking it up in Google).


Just to clarify a few things… To my knowledge and observation Morus nigra is ALWAYS monoecious. However, usually this isn’t visible in a way that the number of male and female flowers is balanced. Normally the species is predominantly female with just a few male catkins hiding under the leaves and they usually go unnoticed. Hence the perception that the tree is female. The balance in flower type can suddenly reverse from one year to the other with almost 100% male flowers and just a few fruit appearing here and there. This reverse of sex is becoming an issue more frequently; at least in my observation. More and more people come to ask me for advice on how to solve this problem… I presume it may have to be linked to climate change. No proof of course but the fact is that it is ocurring much more frequently now…
About M.nigra seedlings and bad root formation: I totally disagree. In my observations M.nigra seedlings make a huge rootmass, more than M.alba the only problem ist that the above ground part doesn’t follow… Especially the part where the collar is where, the root connects to the stem, there is burl formation and it is as though the nutrients which are needed to feed the above ground part never get transported and just make the rootmass grow even more. Finally, after a few or many years the sap flow seems to stop completely and the above ground part withers. Just to anticipate some reactions: there is no fungal infection or rot…just burl formation. A withered seedling still has a very nice healthy rootsystem…


Ok but that doesn’t change the fact that as a result, the only way to get around that is to get a viable caliper stick and graft it onto an alba as soon as feasible