Correct seed:substrate ratio in seed balls?

The plan here is to make a lot of seed balls this winter to seed the alleys between nut tree rows that will be planted at our new place. I am getting some pottery clay as I couldn't find natural clay anywhere near here, and will use a mix of saved and purchased seeds, and our own sieved compost/soil.

My question is: is there a best ratio of seeds to substrate? I'm envisioning meatball sized seed balls. The seeds will be a mix of mostly clovers, pollinator-support and edible perennial and self-seeding herbs and flowers. I think we will hand-form some of these but may switch to making them in the cement mixer if that gets too time-consuming.

Just wondering what kind of number of seeds per seed ball or as a percentage of substrate others have aimed for, to optimize results.

I would think 5 to 6 seeds per seedball. I'm thinking that, cause if they get overcrowded, most will die from competition with each other. I'd aim for the size of a grape, just because that's a common size I see in Internet photos, not because I have any reason to believe that there is an optimal size or number of seeds.

Biology is fuzzy. Anything you do is likely to work great regardless of what the Internet says.

Joseph, that seems reasonable. Grape sized seed balls may be less attractive to most critters than a larger object. I think 5-6 seeds gives a reasonable chance of having enough germinate without overcrowding. I think I would prefer to plant too sparsely than waste seed by planting too thickly. We can always go back over the area again next year if we find it needs supplementing. Or wait for the planted species to further distribute themselves over time.

Making the first batch of seed balls now so I'll document the process in this thread. These initial ones are being made a bit differently from what I hope to be doing in subsequent batches. I had bought some modelling clay for my older daughter to use but she and her support worker tried modelling with it before Christmas and weren't happy with the results. So they handed it back to me to use for seed balls but unfortunately had already mixed the whole box with water and made fist-sized balls wrapped up in clingwrap. I would have preferred to start with dry powdered clay but didn't want ti waste the mixed balls of clay.

So for this first batch my process has been: Remove clay ball from plastic wrap and pick it apart into the smallest pieces possible. This is put into a tray. In this case it is a photographic tray which is what we had. Then throw in a handful or two of soil. I used old potting soil from a pot that had a pepper plant growing in it last summer. If necessary add water. Rub the soil into the bits of wet clay until a consistent texture is reached. Keep adding soil and water as needed until a nice fairly sticky material remains. It is a bit like making a pie dough rubbing flour into cold pats of butter, if you imagine the butter being far stickier and tougher. Eventually the mix reaches a point where it holds together if you squeeze it into a ball.

I will document proportions better once I start making these with dry powder instead of a mixed clay where I don't have the starting info. Besides I think this situation now is not the way most people would do this! I don't recommend it.

The seed balls I am making with this are pretty large. I was given some oats that were harvested for food rather than seed; but they seemed pretty mature so we did a germination test which showed 20-25% of the tested seed germinated. So I am taking at least 5 seeds and making seed balls about the size of a golf ball.

They look like oversized horse apples. Maybe moose apples.

A couple other things I should have said: the clay is Amaco Air Dry clay. What you see in the photo was made with about half of a 10 lb box.

The large size of the seed balls is because the oat seeds are so large. Anything much smaller won't cover 5+ seeds.

Going forward, once I use up this modelling clay I will switch to some red pottery clay I bought in 50 lb bags. If there was clay locally available I would use that but I haven't found any yet. I will also switch over to polyculture seed balls rather than single-species oats.

Edited to fix a typo

A couple other things I should have said: the clay is Amaco Air Dry clay. What you see in the photo was made with about half of a 10 lb box.

The large size of the seed balls is because the oat seeds are so large. Anything much smaller won't cover 5+ seeds.

Going forward, once I use up this modelling clay I will switch to some red pottey clay I bought in 50 lb bags. If there was clay locally available I would use that but I haven't found any yet. I will also switch over to polyculture seed balls rather than single-species oats.