Sunday, February 5, 2012

Starting seeds indoors with soil cubes

 This is the Soil Cube Tool, designed and sold by 
Clayton Jacobs. ( )  
This is a pretty simple design that is practical and
 easy to use. Basically inside the white squares are 
metal plates attached to the bolts. When you push
 down on the handle the plates compress the soil
 medium into cubes and leave a divot for seed
placement. The springs push the handle
 back to the starting position. 

These are the components of the soil medium. The ratio is:
          3 parts peat moss
       2 parts compost
          1 part garden soil
1 part sand 
  1 part perlite
           Add lime if desired
You can also add fertilizer at this point if you wish. 
I would personally use worm castings and some compost tea. 
You can tweak this mixture for making soil cubes 
but I would stick to the ratios and use medium
 similar to the products in the picture. 

I mixed everything together dry in this large "hose" bucket. 
You can get these at your local box store for $4. I then split 
the mix into three buckets so I could make sure it gets mixed 
consistently. Add just enough water to get a thick oatmeal 
consistency. Once the first 1/3 is mixed add more dry soil 
mixture and repeat. I make a lot of this once a year, saves
 time and it doesn't hurt to have extra.

 Press the tool into the mix and press it against the 
side just filling the inside of the tool with the soil mixture. 
Press down on a hard surface, hold for a second then push 
the handle through the tool and the cubes will fall out. 
It takes a bit of practice to get consistent cubes but if you
 mess up just crumble the bad cube back into the mix.

Here is a close up of the cubes when they are done. 
They hold together very well and readily absorb water. 

Here are the same cubes growing tomatos. 
We have 188 cubes started right now. We are growing
 8 types of tomatos, 7 types of peppers, eggplant,
 celery, leeks, 3 types of onions, broccoli, cauliflower, 
brussel sprouts, green cabbage, red cabbage and kohlrabi. 

Place the cubes in a tub like this, it is very 
easy to move them without handeling them. 
You can pour water in the bottom of the tub which 
the cubes will soak up and wick through the cube. 
Don't let them sit in a pool of water, 
use just enough to saturate the cubes.

This is many varieties of lettuce, spinach, cilantro and amaranth. 
They are growing in trays filled with the grow medium. 
You can grow salad greens all year round without 
them bolting or going bitter in the heat.

Here is the whole set up. The lights are full spectrum
 4 foot fluorescents hanging on chains from a stainless
 steel shelving unit. The lights are on a timer set to come
 on at 5am and go off at 9pm. I have heating pads under
 the peppers and tomatos to help them germinate. I use a 
one gallon hand pump pressure sprayer to mist the cubes 
gently so the seeds are not disturbed. 


  1. Looks good. I bought a different model of soil cube maker. I would have tried this last year, but just couldn't fathom the idea that the soil would stand up to bottom watering. But my broccoli plants are doing great and there's very little erosion. The roots are now on the sides of the cubes, but are not jumping between cubes.

  2. Yeah its surprising how well the cubes stand up to bottom watering. It save a ton of time to just pour water in the tub and forget about them for a day.

  3. Do you keep your lights on all day and night? Do you do something different with the light when starting the plants vs trying to grow full plants in the winter?

  4. Hello,

    I have the lights on a timer. They are on for 16 hours off for 8 every day. I use this cycle for the whole time they are indoors. One of the most important things is to "harden" off your starts before you plant them. A couple weeks before you plan on planting you should put your plants outside in dappled sunlight for an hour the first couple days, then 2 hours for a few days and so on until they are ready to plant.

    Hope this helps,


    1. Awesome info, thank you. I had never "Hardened off" (sounds dirty) before, but I can see how that would be good for them.

    2. LOL, my mind went there as I was typing that. My inner monologue added a "that's what she said" as I was typing. =)

    3. Honestly, how could your mind not go there? It's the mans mind that does NOT go there that makes me suspicious. :-)