Sowing depth

define dibber's spike size

Choose the size of dibber’s spike, based on your preference or seed distributors guideline. Before you start some things you should consider:


  • The real depth the spike will achieve is less than the full length of the samples. Part of the spike will be inside the dibber and most of the time there is a gap between the bottom of the tool and the top op the soil in the seed tray
  • To properly test the real depth follow the steps below

Put a small quantity of seeds on the seed grader. Make sure you mix well the seeds inside the bag/container to ensure a good variety of sizes and shapes that truly represent your seed batch:

Shake the seeder until all the holes are full:

Release the seeds and check which hole size will suit your needs in terms of how many seeds per cell you want. Repeat the process a few times to check if the results are consistent in terms of the number of seeds per hole. Seeds should fall easily for the size hole you choose:

If after repeating the process a few times the results are not acceptable or consistent, we can design a seed plate with holes customized for the seed-specific shape and size. Bear in mind that if you’re aiming for a single drop per cell the seed needs to be between 1.5 mm and 12mm and the variation between the smallest size and the biggest size can’t be more than 2 times:

For that, you can use the back of the seed grader.

On the first row place the smallest seeds of the range, on the second row the average seed sizes and on the third the biggest seeds in the range. Take the photo straight from the top making sure light level are good and the picture is in focus.

Then send the pictures to

The examples below are pictures not suitable as they will not enable good results when determining seed shape and size.

Photo taken in an angle, out-of-focus or low-light: