I’ve been meaning to post this description of how we made our vacuum seeder for a while now, but the weather has been so summer-like that we’ve been outside and I haven’t gotten to opportunity to type it up…anyway, not a bad problem to run into in early spring! If you’re not familiar with the basic principle behind the vacuum seeder you can google it to see professional ones in action.
So, other farmers have told us how much use they have gotten out of their vacuum seeders and we wanted to try inserting one into our operation, but we didn’t want to pay the $2500 dollars for a brand new professional quality seeder at this time. I found some plans for homemade seeders online, but they seemed a bit complicated so I simplified them a bit and have come up with this design that has worked well so far, cost under $20 for materials, and took only a couple hours to put together.
The basic idea is to create a box with two chambers – one that will fit snugly around your plug flat and another that the vacuum attaches to in order to suck the seeds onto the holes – that are separated by a piece of plexiglass with holes drilled in it.I made the sides of my box with a 2×8. For a standard 1020 flat size you’ll be able to get all the sides out of one 8′ board. Before cutting that 2×8 into pieces you will want to cut the groove where the plexiglass will fit. If you use a thin piece of plexiglass one pass with a circular saw or table saw will do the trick. 
Make sure you cut the groove so that you have at least a 1/4″ of space above the top of your plug flat. You don’t want the seeds dislodged by accidental contact with your flat. Also, make sure that your line and cut are straight.
After cutting the groove, measure and cut the four sides of your box. Remember that you want the box to fit snugly around your plug flat without touching it. Also when assembling the box make sure that the groove lines up all the way around the edge so that your piece of plexiglass will fit in without any issues. You will either need to cut the plexiglass or measure very carefully and have the hardware store cut it for you.
Before attaching the fourth side of the box slip your plexiglass and plug flat in and mark where you want the holes that will hold and drop the seeds into place.
Next you will need to drill the holes in the plexiglass. For pelleted lettuce seed and other large round seed, you can use the smallest bit in a standard drill bit set, but for smaller seed you will need very small bits that are available in a drill index. You won’t be able to find a drill index at one of the big box stores, but anyone with a well outfitted shop may have a set and they are available online. Also, with the really small bits you’re standard drill won’t grip them. I just wrapped the bit in masking tape and then tightened it up. In the course of drilling the holes I just had to re-wrap the bit once. Once the box is assembled caulk the edges of plexiglass so that the vacuum doesn’t suck any air around the edges of the plexiglass. Then drill a hole where you will attach your shopvac. Ideally you want the shopvac to fit snugly in the hole so that it does not fall out when handling the vacuum seeder. Finally cut a piece of plywood or OSB to fit on top of the vacuum chamber. Once the caulk dries – you don’t want all your seeds sticking to the caulk! – you should be ready to test out your seeder.
A couple tips:
1. It helps to make dibbles in the plug flat before seeding.
2. Sometimes you’ll get more than one seed sticking to a hole. Banging on the back of the seeder will usually dislodge the extra seeds.
3. Lower the seeder slowly onto the plug flat so that you don’t accidentally dislodge seeds before you turn off the vacuum.
4. It helps to pour the excess seeds into something like a measuring cup and then back into the seed packet.
Thanks a lot for this. I really want to build one of these for my farm using your method. One question: when you pour your seeds onto the plexiglass and the vacuum sucks them into their respective holes, how do you remove the excess seed?
You just tip the seeder and dump excess seed into some type of container (we use an old Tupperware container). Since you have to pick up the seeder and dump excess seed if I were to build this seeder again I would use one inch boards instead of two inch boards as mentioned in the directions. This way the whole thing would be lighter and easier to maneuver.
Right on, thanks. I did some more research and saw one seeder where they made a little “gate” in one corner of the seed chamber to let the excess seeds out. Looked like a simple cut in the wood wall fashioned with a tiny hinge. This allowed them to simply open that gate and tilt the seeder towards it, sending the seeds neatly out into a container.
A few more questions:
-What thickness plexiglass did you use?
-How much space is their between the seeder walls and the flat? How snug do you want it to be?
Thanks again. Looking forward to getting this made for spring planting.
Also, if you have any notes on good drill bit sizes for specific seeds, id love to see them.
So after thorough procrastination, I built mine. Problem: I hooked up my home vaccuum and it is way too powerful; the plexiglass bent with the suction and almost cracked. My question is, what do you use for your vaccuum setup?