Why cleaning seed to very high standards is essential.

For the last forty years I have spent a good deal of my life processing seed throughout Devon and Cornwall. In that time, there have been a multitude of critics who have cast aspersions on the whole idea of cleaning seed, saying that it is simply a waste of time.

The aim of the seed processor is to try to ensure that every grain that goes into the bag for sowing will be a viable seed. A pretty tall order, but why would you try for less? The grain is cleaned and separated so that the larger and most dense grains are retained for seed.

It has always been my contention that it is not good enough to just clean seed (and by this I mean, running it through a seed cleaner flat out to tidy it up). It is essential to clean the grain thoroughly and carefully to try to remove as much small and damaged grain as possible so that when you, the grower, plant your very expensive seed, it has every possible chance of growing to be a viable and productive plant.

So, I thought I must establish whether I have spent the last 40 years wasting my time or whether all these years of cleaning seed have been worth while.

During the course of the Spring cleaning process, a very presentable sample of Planet was delivered to the plant. It was locally produced by one of our professional local seed growers.

It is important to explain here that this sample was already fairly clean when it arrived on our doorstep, with very little weed seed admixture. We know that removing weed seeds and diseased grains will make a massive difference, however, I wanted to establish whether there is a link between GRAIN SIZE and DENSITY and plant establishment. So the seed was split into five fractions for the purposes of our test.

  • Fraction 1: Lights and weed seeds (which were discarded)
  • Fraction 2: Less in size than 2.1mm wide
  • Fraction 3: Less in size than 2.3mm wide
  • Fraction 4: Between 2.3 and 2.5mm wide and finally
  • Fraction 5: Greater than 2.5 mm wide in other words, the best seed as you would buy from us.

We planted 4 batches of 100 seeds of each size, in identical conditions in the same soil in the same green house. We now only had to wait and see the difference. It is slightly nerve racking to think that this could show that I have spent 40 years wasting my time!

Within a few days, the seeds started to emerge and from the start it was clear that the differences were beyond anything I had anticipated. The larger grains produced better plants in all respects. Quicker germination, stronger plants and faster growing. It is impossible to show all the results here in this small leaflet, but it is plain to see that in terms of germination, vigour, and root development the larger seeds produce plants that are, on average, many times larger than the smaller seeds.

When looking at the seed tray pictures, you will see that the height of the plant compared to the back of the tray is greater in the larger seeds. The other pictures showing root establishment as well as plant growth are self explanatory. There is a 366% increase in plant weight from the smallest seed to the largest seed.

Even the large screenings (2.3-2.5) produced 55% less plant weight than the larger and denser seed. Bare in mind that in nearly every seed lot, there are light materials and weed seeds before it is cleaned. Planting this material would be an utterly false economy and would dramatically reduce yields.

There is some element of catching up that the smaller plants achieve in the following weeks. However, in the first trial we carried out, the seed was in the ground for three months there was still a clear and startling difference between the batches.

There will always be years when seed size varies, and seed processors can only work with what they have. This trial clearly shows that exceptional cleaning, which is what we aim for at South West Seeds, is not only worth doing but is worth a massive premium to you the grower. We will always aim to give you the best of the seed we have to process.

So, is it worth it?

We have achieved a lot in 40 Years, and YES seed cleaning is worth doing, and it is worth doing well! Use the professionals South West Seeds Ltd

Post By Simon