My 2/3 acre urban homestead has a multitude of volunteer mulberry trees (I assume morus rubra), some quite large that were here when I bought the place 2011.   I pruned them for several years just to get control of everything but have been letting them flourish for 2 years.   This is the first year they've produced semi-large berries so I watched my chickens, the wild birds, and tasted them myself periodically (I'd never had a mulberry before 2 yrs ago which was dried in a trail mix).   Shockingly, [i][b]my chickens are not interested[/i][/b] nor are the wild birds except for a few jaybirds late in the fruiting season.  I've had a carpet of berries under each tree just going to waste but then decided to make vinegar out of them.    .    What flavor profile do you expect with mulberries?   Mild and bland or tangy or super sweet or in between?   I personally find the flavor rather bland and unexciting, but next year will do a proper "shake the tree" harvest as they are so nutritious

https://www.globalhealingcenter.com/natural-health/6-health-benefits-of-mulberries/

I haven't found any discussions here other than mention of planting them.   I wonder if my trees are lacking nutrition (growing in solid red clay), so I'll do a soil test, and...google google:

Stark Bros says this,
 "Iron, zinc, manganese, magnesium, molybdenum, copper, and boron are minor elements that are very important to mulberries. Yet most soils are low in these.
  For best results, find an organic mixture that contains these elements."

I can't find that magic mixture in a packaged product - aaarrrggghhh!    Espoma's Tree Tone"proprietary blend"  product does not specify on their website.  I'm always frustrated when experts say fertilize with this or that but don't offer a source.   Where do you folks find these individual elements?   (probably could be another topic)  

I can't speak for your birds eating the mulberries, but for a mix containing trace minerals I would probably be looking for bags of rock dust. Many soils are improverished, but an addition of rock dust - made as a bi-product of quarrying volcanic stones (granite etc...) can be helpful. The dust weathers solwly, releasing trace minerals to the soil.

In our location we have chalk soils which are sedimentary in origin and even before weathering starts have low trace mineral content. We have applied rock dust to our garden, and while the impact isn't obvious our garden seems more healthy - but it is hard to tease apart from the benefits of good mulching, watering and general care.

Mulberries are supposed to be sweet and taste a bit like a blackberry. If your trees are putting off bland non sweet fruits you need to lay down a good compost mulch around the trees active root zone.
The active root zone for developed (mature) trees starts around 2 feet from the trunk and extends out to around 3 feet past the "drip line" of the branch tips.
I would spread compost from the near point (2 feet from trunk) to at least the mid point.
Other options are mineralization (really need a good microbiome in the soil first) with Rock dusts and Green sand, Epsom salts. (Just about any garden center, Lowe's, Home Depot and Walmart will carry these items)

If you want to speed up this process you can use a garden fork after you spread the compost.
Poke the tines straight down, through the compost and into the soil, rock the fork a few times and move around 6 inches for the next poke of the fork tines.
Do this all over the area you spread your compost, this allows faster "inoculation" ingress of the microorganisms from the compost seeping into your tine holes.
Once you have completed the composting and garden fork work, water gently for at least one hour so the water soaks into the soil, taking some of the compost with it down into the soil.

This will be an ongoing process until you are satisfied with the berry crop taste.

Lack of nutrients in the fruits is why the birds aren't going crazy for the berries, so they are not really worth using at this time, except for adding to the compost heap.

Redhawk

That seems a little strange that the birds aren't eating them. Were they ripe enough?

I highly recommend turning them into mulberry jam. It's positively delicious! Mulberry cordial is also pretty good.

I wish I lived closer - I absolutely LOVE them. I'd come over and eat them for you!!! :)

In 2 years you'll probably be posting for ways to keep the birds off your mulberries haha!

I would be drying them or processing them into something that stores well. Vinegar is a viable option certainly. Don't let them rot is my point. You have a stream of potential income, or at least bartering material literally fall from the sky. Best take advantage of it.

If the vinegar turns out not all that appealing, then either blend it back into some other vinegar, or use it as a feed supplement, cleaner etc. It won't go to waste.

THANKS GUYS!    Yes, I tasted the berries from the time they started turning black until now as they're done.   I didn't harvest them for myself because they were tasteless and I kept thinking the birds should have them once they reached whatever ripeness birds like.  But since they're now all on the ground I'm just scooping them up for vinegar which I use tons of for cleaning, killing weeds, etc.  

I live in a good size city so no one in town (big box stores, or even Tractor Supply and Southern States on the edge of town),  carry rock dust.  They primarily cater to city gardeners and wealthy horse lovers.   I have a hard time buying rocks online on principal so the quest begins.  We do have some landscaping and paving supply companies that sell gravel etc so I'll start there.

Meanwhile I'll be studying - I assume different types of rocks have different minerals so is granite the favorite "all purpose" rock for gardeners?    So many questions so maybe I should instead be asking for references, links or even a thread on rocks here that I've missed.

And yes Nick - I hope so - I'm eager to enjoy eating them myself as well as possibly selling them because they are not offered at my farmer's market :)

Ash if you ever make it to Southeast USA come on over for a cordial (another research project, haha!)  

Thanks Bryant - knowledgeable and thorough as always :)

Granite rock dust is good but keep in mind that granite will create a slight acidity in soil the dust is added to, just add small quantities at a time and all should be fine.

I found some ground up basalt here in Arkansas and it was very nice mineral wise.

Sea-90 is also a nearly complete mineral additive, 95 minerals are in this product and it will last in the soil for over three years from a single application.

Minerals are minerals, there is no such thing as "organic minerals".

Any of the bigbox stores near you should carry "micro nutrient" fertilizer which will contain most, if not all, of the elements you listed.

Same happens here .Loads of wasted fruit on the ground.Now the bigger fruit has been left on the branches.My sister was really amazed by the taste of this fruit and couldn;t believe it was so sweet.I don't know whats going on.

Wood ash is a good mineral fertilizer.
Only  pure wood ash! Not treated wood!

Interesting Dirk,   this is one article I found    http://vric.ucdavis.edu/pdf/fertilization_Woodashes.pdf

I have wood ash from the pecan trees on my property so not likely it would contain nutrients that the mulberries are not already getting?

Not finding anything in my big box stores that specifically list the minerals.   Do you know a product name I can look for Peter?

Too much water or rain will cause mulberries to tasty watery and unflavorful.

We did have a very wet May, almost no sunshine for a couple of weeks.  But are birds that picky about flavor?    I'll monitor that next year.   Meanwhile I'll fertilize and mulch heavily.

Susan,

There are three species of mulberries around, and hybrids from at least alba and rubra as far as I know, maybe all three (although I think nigra has different chromasome #). Some will be "spitters" I expect. I have clay soil and the berries are mostly fine, but I also have been aggressively using wood chip mulch. The mulberries are ungrafted and I am not even careful about having it near the trunk, just trying to increase the soil microbes and the minerals will likely be around in sufficient quantities. I do use rock dust but I think mostly that is a psychological vestige of my academic training, because I measured I had to "fix" the deficiency. The more I do this the less I think those are overly helpful unless very deranged.

Just provide tilth through soil microbes, plants are not as picky as we make them out. My soil has eaten inches of wood chips and is perking up nicely. The mulberries grew so fast last year in tubes I had to cut them back to 4' from 7-8' because the trunks were not able to support them, they were 1' whips in April last year. Then this year the deer pruned them for me with the tubes off. I use the mulberries to keep the deer off the other stuff, they LOVE them.  

Thanks TJ - that's encouraging because we seem to have similar conditions, although I know the clay soil at my house is very different from the clay soil at my friend's 3 miles away.    I'd like to not have to worry so much about individual nutrients by percentage in different conditions for different plants.....on and on.....my head is swimming from so much reading in the past 5 years that I can't make sense of it all.   In studying nutrition I know that sometimes if adding one thing to the system, it can cause problems for something else and it's beyond my feeble brain to sort out that matrix for my body or my garden!  

So  I looked up Sea90 (recommended by Redhawk) and think I'll go that route for now in addition to tons of oak and maple leaves and woodchip mulch.    I've not studied minerals before but am delighted to learn that sea salts contain so many minerals that I need in my body (real deficient in magnesium),  my pecan trees look healthy but the pecan quality is variable, my blackberries never quite get sweet,  and my vegetable garden produces horrible bitter greens so I just might spread those minerals everywhere!   It sounds like Sea90 will give me a faster and more comprehensive boost to the soil for next year.   And I STILL can't find a local source for rock dust!

Here's an interview with the SeaAgri Company founder.    Interview starts at 6:45    

Susan Pruitt....
If you are in NC....near Mt. Airy.
You can get granite dust by the bag in Mt. Airy at the N.C. GRANITE CO.
Last time I bought it was over 20 yrs ago....

Joe B.

Interesting. My black raspberries started tipping from sweet n' tart to just tart around the time the nearby grape vines took off.
I find my chooks are spoiled. They will not eat a lot of anything at once,and some things,like white bread, they mostly just ignore.
How much do you do you feed them?
Maybe they need to be little hungry to appreciate these berries.

Btw, the dried leaves smell amazing!

Susan,

Don't be intimidated, none of us are Elaine Ingram and only one of us is Bryant. There are some great suggestions on here. I used to buy Azomite, test every six months, yatta yatta. Then I got busy with other projects and realized that any difference was marginal at best between what I babied and what I neglected. If you can get the rock dust locally that is what your soil was before it got depleted- soil is weathered bedrock almost everywhere. That makes sense to maybe recapitulate the former composition. Then the local plants should be happy- BUT they might be happy anyway. I wouldn't be too crazy.

People concentrate on feeding the plants. The plants are not hydroponic, they are in constant interaction with the soil microbes. They will do all that work for you! Feed 'em up and let nature blast off. If you want to move up a notch look at Bryant Redhawk's posts and see what you can do with compost tea for a power boost! You can throw some minerals in there (I use a little azomite powdered I found in my garage that goes through the sprayer when I remember). Just feed the soil organisms and the trees and bigger stuff will thank you. And this is a good time in the south to top dress with some chips and compost to feed the beasties before it gets dry.

And i did put down 100# Sea90 per acre over the last couple years to replenish the microminerals and was liming before with dololitic lime (just another rock dust) so my magnesium was OK. If you just need magnesium Epsom salts are easy, but I like lime since it has a fuller complement of minerals.

Very good points Tj, Mineral additions are really only useful to get things going, once you have a good soil microbiome going you really don't need to make anymore additions of minerals.

Most people would like to get a first year crop of something, that is when any additions are most useful. Once you have worked at building the microorganisms in your soil, you might even do detrimental things by adding more minerals.
That is something I am looking into right now, what is the "too much of a good thing" level and what happens when it is reached in good bioactive soil.

Redhawk