Inventing the perfect seed starting trays?

[palewine]

I did a bunch of research on whether to use soil blocks or traditional seed trays. I ended up going with trays, but wanted something that had the "good parts" of both:

- air pruning (from soil blocks)
- ease of filling, watering, and using (from seed trays)

And none of the downsides:
- having to make a specific soil consistency (soil blocks)
- doing the same mechanical motion over and over many times (soil blocks)
- worrying about the block falling apart if you don't water it correctly (soil blocks)
- plastic (trays)
- trays breaking after a few seasons (trays)
- root bound plants (trays)

I didn't see something that met these ideals. So I decided to invent it! At least, I'm going to try. Here's what I'm thinking:

I want something that will:
- hold soil in place (like a traditional tray), but
- allows air to permeate on all sides (like soil blocks), and
- is not plastic (I'm trying to get away from plastic near my food as much as feasible). Bonus if it
- allows water to wick up for bottom watering.

My idea is to use food-grade stainless steel mesh to form the "pouches" to hold soil. With some solid stainless steel rings at the top to help hold their form, and join them to neighboring cells/pouches.

I bought some 400 mesh to test the idea. It might end up being too fine (too fine = not enough airflow... going to also try 20 mesh and compare seedling results). Still playing with shape and size too. I made 3 possibilities (warning: ugly prototype incoming). Cylinder, square, and a pouch. None have solid rings yet, but that can come later. Pictures attached.

Looking for feedback! Do you think this will work?

 

[oneeye]

I did a bunch of research on whether to use soil blocks or traditional seed trays. I ended up going with trays, but wanted something that had the "good parts" of both:

- air pruning (from soil blocks)
- ease of filling, watering, and using (from seed trays)

And none of the downsides:
- having to make a specific soil consistency (soil blocks)
- doing the same mechanical motion over and over many times (soil blocks)
- worrying about the block falling apart if you don't water it correctly (soil blocks)
- plastic (trays)
- trays breaking after a few seasons (trays)
- root bound plants (trays)

I didn't see something that met these ideals. So I decided to invent it! At least, I'm going to try. Here's what I'm thinking:

I want something that will:
- hold soil in place (like a traditional tray), but
- allows air to permeate on all sides (like soil blocks), and
- is not plastic (I'm trying to get away from plastic near my food as much as feasible). Bonus if it
- allows water to wick up for bottom watering.

My idea is to use food-grade stainless steel mesh to form the "pouches" to hold soil. With some solid stainless steel rings at the top to help hold their form, and join them to neighboring cells/pouches.

I bought some 400 mesh to test the idea. It might end up being too fine (too fine = not enough airflow... going to also try 20 mesh and compare seedling results). Still playing with shape and size too. I made 3 possibilities (warning: ugly prototype incoming). Cylinder, square, and a pouch. None have solid rings yet, but that can come later. Pictures attached.

Looking for feedback! Do you think this will work?

Very interesting post, friend, thank your for sharing. I just use dixie cups for my seed starting. I'm wondering how much aggregate you will lose if any with the mesh vs plastic?

 

[palewine]

Aggregate... do you mean soil? If so, the current 400 mesh won't lose any at all - it's much finer than I expected it to be actually. I need to also get some "looser" mesh to compare. The ideal would be just barely fine enough to keep soil in, but no more, to let air in. I suppose other factors (in favor of finer mesh which provides more coverage) could involve retaining moisture and possibly water wicking.

 

[dirty hands]

Will the roots stick to the mesh to much?

 

[Chuck]

That stainless steel mesh sort of reminds me of peat pots. The roots will grow through it and to get the plant out of the mesh pots you will have to tear the roots lose, damaging them. The only way to avoid this is to remove the young plants early which could be detrimental. I would rather have root bound seedlings than I would a damaged root system. I would not purchase something as you described.

 

[palewine]

@dirty hands and @Chuck interesting that you both had a similar initial reaction. I actually hadn't thought of that, but you're right that is a concern.

I guess I won't know for sure until I grow something in it as an experiment! I plan to try a few sizes - 20, 100, and my current 400 (the higher the number the more densely threaded the mesh is, it's 'count per inch').

And I'll do a regular plastic tray as a "control." I guess I should also do a soil block to compare it to... although I don't have a soil blocker. Maybe I can just make a few blocks by hand?

 

[Ruderunner]

Cardboard egg cartons would fit most of your goals other than reuse.

 

[Chuck]

@dirty hands and @Chuck interesting that you both had a similar initial reaction. I actually hadn't thought of that, but you're right that is a concern.

I guess I won't know for sure until I grow something in it as an experiment! I plan to try a few sizes - 20, 100, and my current 400 (the higher the number the more densely threaded the mesh is, it's 'count per inch').

And I'll do a regular plastic tray as a "control." I guess I should also do a soil block to compare it to... although I don't have a soil blocker. Maybe I can just make a few blocks by hand?

I wouldn't worry about a soil blocker. Most folks who bought one no longer use them.

 

[dirty hands]

It needs a small coffee filter insert that can be lifted out easily for planting.

 

[Martin Mikulcik]

Trays don't have much water so need to be watered frequently and getting rootbound isn't really so much a problem because you'll have to repot them anyway soon enough.

Honestly, if you don't need to start 6 weeks before last frost, sowing outside in the soil works pretty darn good. Otherwise I'd be making deep trays out of wood or something. Lack of air isn't usually a problem in shallow trays with soil coarser than ball clay

 

[palewine]

It needs a small coffee filter insert that can be lifted out easily for planting.

Oooo that's something I hadn't considered before... simple thin paper, easily biodegradable. Interesting idea!

I was hoping to have the wire mesh be flexible enough to just push and pop the plants out. Almost like fabric. The trick there, as I'm noticing from the wire mesh samples I'm obtaining, is that some mesh is not very flexible. So I need to find one that's the right "fine-ness" and the right firmness.

Getting the shape right will be important as well, because my cylinder shape looks nice but is not easy to push up from the bottom.

Cardboard egg cartons would fit most of your goals other than reuse.

The big thing I'm interested in from soil-blocking-world is air pruning. Would a cardboard egg carton have this effect? I would think not since it's a solid-ish thing; doesn't let enough air in. But I haven't tried it.

I wouldn't worry about a soil blocker. Most folks who bought one no longer use them.

Interesting observation. What are the reasons you've heard that people stop using them?

Thanks for your thoughts so far, all!

 

[Sluggy]

Sadly I have never had any luck except with plastic flower pots or seed trays. No idea why as other methods should work.

 

[big rockpile]

I wouldn't worry about a soil blocker. Most folks who bought one no longer use them.

Got two somewhere.

big rockpile