May 02, 2026

Seedling Starter

This project is a seedling starter for growing plants from seeds.

Normally when growing stuff from seeds I just use the tried and true method of placing seeds in a wet paper towel and placing them in a zip lock bag until they start to germinate and then planting them in the soil from there.

Last year (2025) I happened upon this seedling starter on Thingiverse designed by mandooooooo.  I was a little hesitant to try this because the they used AI for the main images but after looking at the Thingiverse Makes it looked like it was at least printable although at the time no one showed anything growing in it.

There were 3 sizes available for download but seeing as I wasn’t sure it worked I opted to start with the smallest one.

Here is the printed 2×2 tray and seedling pots.  The original pots fit way to tight in the tray so I reprinted them at 95% scale.

After adding potting soil and the water bottle I waited to see if anything leaked and if the soil because moist.

The next day after everything looked good I first tested it with some already germinated sunflower seeds to see if they would survive the constantly wet soil.

That first test batch resulted in 3 of the 4 seeds growing. In 2025 I also did several more sunflowers from just seeds and those all grew great so the system works great.

The original pots while being a little to tight were also solid so removing the seedlings to plant was a little challenging even though the pots are tapered.

Another Thingiverse used came up with the idea of using a disc in the bottom so you can easily press out the ready seedlings so for 2026 I printed up the new pot design to try. (the new ones also fit perfect in the tray now.)

I also went ahead and printed the 2 x 6 version.

The system worked so well and mandooooooo provided a step file for the designs so I took that and made a 28 pot version. With the bottle in the center I should also be able to use it as a handle to move the tray around when the seedlings are ready to pot.

I used locator tabs for each pot too so when moving around to plant the remaining pots will stay in place.

Here the pots are all filled and ready for seeds.

For 2026 I decided to try a few different flowers to see what else will work besides sunflowers.

I also used a larger bottle on this version because there are more pots to soak up the water.  Now I just need to wait a few weeks to see if anything sprouts.

While I’m waiting for the seeds to grow I designed this totally unnecessary seedling planter to dig holes in the shape on the pots.  It’s modeled after a bulb planter so after you dig the hole it spreads opens to release the dirt easier.

Here are the printed parts ready for assembly.

I am using rivets made from filament for the hinge pins. I just heat the filament with a lighter for a split second then press the end with something metal to flatten one end.

That then gets inserted through the hinge.

Holding it in place I then trim off the other end leaving about an 1/8″ exposed and then heat and melt the trimmed end to from the rivet in place.

Here is the finished rivet. Now I just repeat that for the other side.

4″ long aluminum rods are used for handles (although wooden dowels would probably work too). The Rods and the finger tips are just super glued in place. I was going to make a spring loaded single handle like on a bulb planter but this thing is all ready overkill as it is so I’ll just use two hands with the simple finger tips.

Here is it spread open.  Again this thing is totally unnecessary but it was still fun to design.

Quick test of the Digger.

I used one of the old pots as a test so the finished seedlings should fit perfect.

It’s only intended for use with soft dirt but time will tell if it stands up to digging 40+ holes for the plants I have already started.

One week in and we have some sprouts.  The Zinnia is off to a strong start (left), A few of the Nasturtium doing all right (center), and the Cosmos (right) is just starting to take a peak I think.

Two weeks in and the Nasturtium as really taking off. All of the Zinnia have germinated, 5 out of the 8 Nasturtium, but only 2 of the Cosmos. I don’t think they like the moist soil that well. The only two that germinated are were there was the least water in the tray. Time to try planting.

I’m planting the nasturtium in a 14″ planter barrel. The digger worked ok and actually worked better opening it, plunging into the dirt, then closing it to remove the dirt.

The roots are well established I’d say.

The new pots with the push out disk make removing the seedlings very easy. (it’s probably best to let the soil dry out a bit before removable to keep their shape.) Some of min were really moist and started to fall apart.

Five might be to many for the pot in the long run but we’ll wait and see if they grow now that they are outside.

I planting some of the Zinnia in another flower box as well as a few around the yard in garden beds.

To be Continued…

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