We have been asked to share a recipe for seed compost but, as always happens, it turns out there is far more to it than we originally thought…

Marina Christopher’s Seed Sowing Compost Recipe

“I mix equal parts of a sterilised peat-based seed compost with a soil-based John Innes formula (it really doesn’t matter if it is grade 1, 2 or 3) and a 1-3mm washed grit. This is all passed through a large mesh sieve (approx 1 sq cm) to remove the largest particles. Mix it all up in a large clean wheelbarrow and you get a heavy, gritty, open compost which will be free draining but moisture retentive.”

There you go – your seed compost should be open and heavy – and Marina Christopher is someone to listen to.

Yeo Valley Farm

Searching around we found a seed compost recipe from these yoghurt makers. They use half horticultural sand and half sieved leaf mould. And talking of leaf mould…

Our New Zealand Friend Bronwyn, Nurserywoman

Growing up in New Zealand it was not possible to just pop over to a retail park on a Bank Holiday weekend and get a 3 for 2 deal on screened, branded compost. So when they grew plants from seed (and they grew all of their own plants) they had to use what was on hand.

Her father built a shade house using the trunks of tree ferns stuck vertically into the ground. There are a lot of tree ferns in New Zealand and these trunks would root again and start growing. A sheet of corrugated plastic went on top to allow in some light for the raised beds where her mother grew ‘water fuchsias’… this was a localised parlance for Impatiens.

This is what we love about talking with Bronwyn – there is no standardised language of gardening, no formality – you learnt what something was by growing it and named it by what it did. So the shade house her father built became known as the Punga House, because Punga is what they called tree ferns. (Google ‘Punga’ and it turns out to be a part of the Maori mythology, a God of all things deformed…)

Every Autumn her father would sweep all the leaves from the garden into the Punga house and leave them there to rot down into leaf mould. It was never watered or turned over, just left alone.

Then when Spring came he would stick a spade into the bottom of the heap and use the crumbly mixture for his seeds by mixing it up with the rich earth sieved from the vegetable patch. It worked, and we imagine it to look much like Marina Christopher’s recipe above – open (from the texture of the leaf mould) and heavy (manured soil from the vegetable garden.)

For a long time Bronwyn worked at one of the leading plantswomen’s nurseries in this country. She told me they stopped using a peat-based seed compost but went back to it because it hadn’t worked very well. But non-peat composts have changed considerably lately and so the nursery in question are now changing to a peat-free mixture by Melcourt (which you can buy yourself by clicking on the picture below.)

Christopher Lloyd’s Compost Recipe

We spent a day at Great Dixter a few years ago on the propagation course they run, where we spoke at great length about what compost to use.

Christopher Lloyd had a soil steriliser (that still sits in a shed at Dixter, and that the current nursery manager calls ‘dangerous’) that he would use to get rid of weed seeds from the soil taken off the fields each year. To this would be added grit, composted bark, peat and a slow release fertiliser. He also used soil from molehills too.

The Great Dixter website explains why they make their compost this way, with such a high loam content:

A) Plants establish themselves more easily in the garden. Because our compost mirrors garden soil, plants raised by us do not experience the trauma of having to make the transition from a pampered life growing in a soft rootzone to the reality of life in ‘real’ soil. Plants in our compost grow tougher and are better prepared for garden situations.

B) Loam contains natural nutrients and trace elements essential for healthy plant growth.

C) There is better drainage/moisture retention balance.

D) It is much easier to re-wet if it dries out.

A case of grow your plants hard?

Seedballs

For a mini eco-system that provides everything your seeds need, how about using Seedballs? We started selling them at a Farmers Market this year and they were incredibly popular – many adults bought them to use in shallow, dry soil near driveways while children loved to rattle the tins the seedballs come in.

The idea is a great one – take some clay, add the seeds you want to grow, then mix it with a little compost and chilli powder (this stops the birds from eating the seed) and roll it into a ball. Throw onto bare soil and let the rain do the rest of the work in aiding germination!

It was Masanobu Fukuoka who revitalised the idea recently, when he used them to save labour on his farm in Japan.

Seed Sowing Compost: A Conclusion

Our research has thrown up more questions than it has answered – people suggest a sterile growing medium is necessary so new seedlings don’t get battered out of the way by weeds. Should we also use a sterile pot then? Or sterilised water? What about the air around us?

Yet we are also told to find a molehill and use the soil from that… where do you find a sterile mole hill? Can we get them online?

The next question is whether we should use peat or not? If you do use peat, where is it from? After all, not all peat is the same and where it is sourced from will give it a different quality that may or may not help your plants to grow.

For us, we prefer as little input as possible when growing plants (because time is precious to us and, more importantly, plants want to germinate and grow. Set them off and then get out of their way!)

So we suggest taking Marina Christopher’s advice for a seed sowing compost – make something yourself that is both heavy and open. Use soil for the heaviness, the water retaining capability, then add grit, sand, perlite, composted bark or leaf mould to open it up. Don’t worry about using a sterile soil (although roots of pernicious weeds are to be avoided…) and you shouldn’t need fertiliser either.

Experiment, see what works for you and do let us know how you get on with your seed sowing compost recipes… before we go though, we have a little word about compost from…

Ken Thompson, Botanist

“Garden soils contain too much phosphorus and too much potash (most gardeners use far too much fertiliser) but few have enough organic matter, so make and use as much compost as you possibly can.”

But we’re sure, being the fantastic gardeners that you are, you already do that.