Sowing Seeds and Compost

Like many people here in the UK I’ve been sowing seeds. I give myself extra work by growing almost all of my early plants in  modules. This keeps my plants away from slugs, voles, birds, and the worst of the weather, and allows me to give the optimum tmperature for germination using electric propagators. In fact if I had been sowing seeds outside this Spring I’m not sure how many would have made it. As well as needing a bit more work, sowing seeds in  modules, rather than sowing them directly in the ground, creates the need for a suitable growing medium. I had read a book which suggested that mixing dried cow manure and river sand makes a good seed sowing compost, but I don’t have either to hand. In the past I have relied on bought in ‘multi purpose’, sieved and mixed with sand, but with the volume of seedlings that I grow, and the trees and shrubs in pots, this is expensive, not particularly ‘green’, and may in fact be responsible for creating some of the disease problems that seedlings suffer from. This year I have made some changes to the way that I go about sowing seeds.

Healthy Soil and Sowing Seeds

A 5 – 10% level of organic matter in soil is considered good for agricultural purposes, yet many ‘bagged’ composts are almost 100% organic matter, especially the organic/peat free versions. With organic matter holding water like a sponge, using these for sowing seeds means that your seeds will be sitting in waterlogged conditions, which isn’t healthy. Mixing these with sand helps to improve aeration and drainage a little, but this still doesn’t resemble the conditions in which the seedlings will be growing, or should be growing in. Another problem with many bagged composts is that they get wet, and then stay sodden for long periods, potentially encouarging anaerobic microbes, some of which could be harmful to my seedlings. This link describes damping off. I don’t agree with most of the treatment and avoidance measures that they list, but the damp conditions and over fertilisation sound just like the conditions created by wet organic matter.

I have resisted using soil from my vegetable beds, concerned about weed seeds, pests, and disease, but this is not really sensible. A healthy soil should contain everything that a seedling needs.  The question has been how best to handle it?

Weeds and Sowing Seeds in Modules

I have been concerned about using garden soil as a growing medium for sowing seeds as I felt that it may lead to me introducing pernicious weeds into the vegetable growing areas, but if the soil is coming from those areas initially, I will only be moving weeds that I already have, and none of those have been a significant problem so far. In practise, as long as when you are sowing seeds you know what the seedlings will look like, anything else is unwanted, and can be plucked out, or cut with scissors. It’s particulary easy for seedlings like tomatoes and brassicas, which are easy to identify. Sowing seeds in little clusters is another way to help with the identification of weeds. Once you can see what the seeds that you have sown look like, anything else can be removed.

My New Seed Sowing Medium

I could have taken some of the soil from my growing spaces to use in my new medium for sowing seeds, but a more simple solution presented itself. I have been collecting the soil that our moles throw up. This has been used as a component in the mix that I make for growing trees and shrubs in pots. I decided that I would use it as the bulk component in my mix for sowing seeds. The soil comes from the top 12 inches under permanent grass. This means that it already has a pretty good organic matter content, and probably a good mix of microbes, good and bad. As we are on a clay subsoil, using this on it’s own leads to the clay fraction filling the pore spaces when it is watered in pots or modules. To keep them open I use sand, some of my own thermal compost, some worm compost, a small amount of Rockdust, and some ‘bagged’ compost.

Making the Seed Sowing Mixture

I use two riddles to separate the different sized particles. The largest has mesh that is about 6mm. The mole hill soil is riddled with this size. Anything that doesn’t pass through the sieve is put to one side and used as the bottom layer in pots and modules, or in larger pots. I do the same with my own compost, vermicompost, and bagged compost. I add sharp sand to these smaller particles. I am aiming for about 75% soil, and 5% each of the others. This isn’t precise. This mixture provides the bulk of my compost for sowing seeds. When mixed I take some of this mixture and pass it through a smaller mesh riddle. This is about 3mm. This will be used to cover the seeds once they have been sown. I use the same sized riddle to add rockdust to the fine mix. Anything that doesn’t pass through the riddle goes back into the bulk mix for sowing seeds. I have used charcoal for to add to seed sowing mixes, but haven’t riddled mine yet and it still has too much wood ash in it. The wood ash will add minerals, but is very alkaline, and too much would not be good for seedlings.

Rockdust

I would like to replace all of the sand with rockdust, but it costs 4 times as much. I use it in the top layer only, for it’s mineral content. I stick to the sand for most of the mixture, for it’s improved drainage and aeration.

Other Soil Amendments

I have some bonemeal, and fish, blood, and bonemeal that I can add to the mixture. However I think that the seedlings don’t need too many amendments. I tend to use these for plants that are going to spend prolonged periods in pots. My preference would be to replace the bonemeal with rock phospahate, but this is also expensive to buy in smallish quantities. My early trials with compost tea showed that it gave an initial boost to seedling growth.

Beneficial Microbes and Compost Tea

Whilst a healthy soil should contain plenty of beneficial microbes, I use compost tea to water the modules initially. I also use a highly diluted compost tea to water the seedlings. When the weather is cold, it’s difficult to multiply (brew) microbes in a compost tea brew. So I mix vermicompost, liquid seaweed, and molasses together, and water with it. Sowing seeds into modules that have been watered with this mix, and which are then put into a warm propagator, should create the same conditions. I think that this is important. Plants secrete sugars from their roots, which then feed microbes. These multiply, and are eaten by nematodes and protozoa, releasing nutrients that the plants can use. By adding simple sugars (molasses), minerals (seaweed), and beneficial microbes (vermicompost) I aim to start that process early. By the time that the seedlings are producing a surplus of sugars, there should already be a healthy population of microbes present.

Mycorrhizal Fungi

If I have any commercially produced fungi to use, I do sprinkle some around the seeds, but I tend to save this for the more important plants. Although Vermicompost tends to be bacterially dominant, if the worms are fed with more woody material, the fungal component can be higher.

Results

Sowing seeds using my latest seed sowing mixture have been good so far. I hope that this will improve when I start to add more crushed charcoal to the mix. The real test comes when the seedlings start to get crowded and stressed. This is when damping off is most likely to occur. I always hope that having a healthy population of microbes will help, but have little way of confirming that without side by side testing.

I hope that this post has been useful, interesting, or thought provoking. Let me know what you think

Take Care

Deano

 

21 thoughts on “Sowing Seeds and Compost

  1. Patrick Whitefield

    Thanks for this window on your gardening methods, Deano.

    Myself, I haven’t sown a seed yet this spring. I feel early April is soon enough. Early sown seeds often suffer a check and later sown ones can catch up. Seedlings which suffer a check often reflect this later in life with poor growth.

    As for compost, I’ve had good results from a mix of 2 parts fertile topsoil, 2 parts municipal compost and one part sharp sand. I can’t really say it performs any worse than purchased seed compost.

    I think the reason for damping off is usually overwatering. It’s hard to get it right, but I find something which helps is watering from below rather than from above.

    I’ve got lots more thoughts on the subject of seed sowing. Too much for a comment box on your blog, Deano, so I think I’ll write a post on my own blog on the same subject. http://patrickwhitefield.co.uk/blog.php

    Reply
    1. Deano Martin Post author

      Hi Patrick
      Thanks for that comment. I like to get some seeds started early, and then keep on sowing batches through the season. I’ve been sowing seeds of tomatoes/chillis/aubergine which need a longer growing season, and will be grown under cover, hopefully in a new polytunnel.
      The other stuff planted now is primarily salads, with a few onions.
      I’ll read your post when you’ve finished it.
      Wishing you well.
      Deano

      Reply
    2. Tom

      Some of us have found it intolerable waiting for spring to come, april might be prudent but Ive always been daft wasting seed under cloches in late february. I also overwinter a lot of seedlings ready for the spring, under cloches in my leanto or in the living room. I’ve done this successfully with coriander and spinach which I can be munching on while the spring sown seed catches up.

      Reply
      1. Deano Martin Post author

        Spring does seem to have been a long time coming. We have salad on the windowsill. I keep my early sowings, and many of my late ones, in modules. It is a bit more work, but I hate sowing seeds into cold wet soil. It doesn’t work well
        Cheers Ton

        Reply
  2. louise penygraig

    thanks for another helpful post. I haven’t digested it all yet, but may try some of your ideas. So far I’ve not experimented with my own mix and have used bought in compost – mainly New Horizons organic. however I’ve not yet succeeded with brassicas – they start off fine and then die. I’d decided it must be damping off disease, but every thing else is fine. Your post explains why this might happen. I’m experimenting with Carbon Gold seed compost for some of my seeds this year, but it is expensive and I’d like to be more self sufficient in the long run. I hadn’t thought of using soil from mole hills. If the weather ever improves (3″ snow here today) I think I’ll go out and get some. I love that you do all the experiements that I don’t have the energy for – I struggle just with growing the stuff as it is! Best wishes
    Louise

    Reply
    1. Deano Martin Post author

      Hi Louise
      It doesn’t feel like a seed sowing experiment until I think about it afterwards, and reflect. I always just look at the problem, identify what needs to change, and then change it. I avoid using mole hills from any area that has pernicious weeds, but haven’t had a problem yet.
      You may be able to use mole hill soil, with a small portion of the bought in mix, especially in the very top layer. Mimicking nature.
      Good Luck, ans why not try splitting your brassica sowings into two and compare them? Not a lot of extra work, but useful information.
      Hope that it goes well
      DEano

      Reply
  3. Hilary

    Hi Deano – i read with interest your seed sowing experiences. A couple of thoughts – have you considered making seed compost to an adapted John Innes recipe using your own sterilised loam, which is not too difficult. For sterilising soil to kill pathogens and weedseeds see http://www.hdc.org.uk/sites/default/files/research_papers/PC%2034%20Final%20Report.pdf
    For John Innes seed compost, take 2 parts of sterilised loam
    1 part peat (I guess you could sub in your own compost, leaf mould, coir) plus 1 part sharp sand
    All put through a 9 mm gauge sieve
    Add 0.6kg of ground magnesian limestone and 1.2 kg of superphosphate per 1 cum of mix – this bit may need your own input. Hope it helps. Best wishes Hilary

    Reply
    1. Deano Martin Post author

      Hi Hilary
      I have toyed with the idea of sterilising soil for seed sowing mixes, but my wife won’t allow soil in her oven, and I don’t want to spend money on a soil steriliser. In the end I figured that picking out the odd seedling from my modules is not a lot of effort.
      The mole hill soil saves me having to do a lot of work, and keeps the place looking tidier too.
      I’ll lave the link in your post as it may help somebody else though, thanks for sending it.
      DEano

      Reply
  4. Tom

    Am I right in thinking that John Innes compost is turf that has been stacked, covered and rotted? Nice little permaculture technique in itself and a hundred years old I believe.

    Reply
    1. Deano Martin Post author

      Hi Tom
      I’m not sure that’s right. The loam part of his original formula may have been, but there are other ingredients.
      The process that you describe is certainly a good way to make the bulk of a mixture.
      DEano

      Reply
  5. MikeH

    If I have any commercially produced fungi to use, I do sprinkle some around the seeds, but I tend to save this for the more important plants. Although Vermicompost tends to be bacterially dominant, if the worms are fed with more woody material, the fungal component can be higher.

    From my research, making sure that you have good mycorrhizal content in your soil is very important. Plants are more disease and drought resistant. I bought a water soluble inoculant. All the herbaceous perennials that we are planting get 350 ml of solution at the time of planting. And I’m having a go at producing my own by inoculating some pots of oats using a sterile seed starting mix. The oats will winter kill leaving the root ball for inoculating new plantings. Testing will be an interesting problem. There are labs that do mycorrhizal colonization testing but I think I’ll probably do a simple with/without test.

    I’ve already done a with/without test on some Miscanthus giganteus that I’m growing for compost. The half of the planting that was inoculated is noticeably taller than the half that was not. It’s clearly not a rigorous test, In fact, it probably doesn’t qualify as a test but ………………..

    Regards,
    Mike

    Reply
    1. Deano Martin Post author

      Tests like the one that you describe are good enough for your/our own purposes. If you see a difference that’s all that really counts.
      It will be the same for your own inoculant. If the plants benefit, then something is working, and that may be all that you need.

      Reply
      1. MikeH

        I got the inoculant from Bountiful Gardens – http://www.bountifulgardens.org/prodinfo.asp?number=SMY-9377#.Ug0m3HNDvI8 . When I queried them about the fungal species included, they relayed an answer from Paul Stamets’ company – http://fungi.com/ so it looks like that’s where they are sourcing their prodcut. Don’t know if Bountiful Gardens ships to the UK but if they don’t and you are interested, let me know and we can work something out.

        Regards,
        Mike

        Reply
        1. Deano Martin Post author

          That does look interesting. As there are plenty of mycorrhizal fungi that have edible fruiting bodies, I wonder if this mix has them in. Any chance that you could send me the list of species included, so that I can compare it with the list of edible species?
          Cheers
          Deano

          Reply
          1. Deano Martin Post author

            None of those appear in a list of edibles, but it is the best mix that I have seen so far. I had a quick look at the website. I’d love to try some. The one oz seems a bit small, but wouldn’t want to risk paying for a 1 lb jar and having it confiscated. Most of these companies won’t ship to the UK, and I’m not sure if it’s legal. I’ll take a look to see if I can find something comparable.
            Thanks Mike

          2. MikeH

            I think that growing your own is the way to go. There are a number of instructions on the net including this UK site – http://www.sunseed.org.uk/research-archive/. It’s a bit random in the sense that it starts with starter soil. This article – http://www.gwinnettmastergardeners.com/2007/11/mycorrhizas-the-underground-internet.html, is a bit more specific.

            Right now, I have four 8″ pots of oats inoculated with the Bountiful Gardens water soluble product. The idea is to let the oats winter kill and have the entire soil ball in the pot available as inoculant. For soil in the pots, I used a somewhat benign mix of peat moss, perlite, and a bit of supermarket compost which is fairly diluted, weak stuff. I’d like to know whether I’ve got mycorrhizal fungi growing in the pot so I’ll send some to a lab for testing next spring. It’s fairly easy to find a lab that will do mineral soil tests but quite a bit harder to find one that will do biological soil tests. Notwithstanding, I found one that will do a Mycorrhizal Colonization test for $42. If I get results that I’m satisfied with, then I will have removed an external dependency.

            Let me know how you make out with finding a source.

            Regards,
            Mike

          3. Deano Martin Post author

            There are similar instructions on the Rodale site.
            I was not seeing good germination of rye seedlings on wet paper. They were part of a pre-spaked batch left over from planting a up bed outside. I was worried that they were somehow not viable, but then saw that the sown seeds were germinating better and faster than the ones on paper. I then read in Mycelium Running that the endophyte Piriformospora indica improved the germination of wheat seedlings from 57 to 95%. Having grown grains on the same bed for the two previous years, I can only guess that this fungi is responsible.
            Fascinating stuff.

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