It’s that time of year - everyone is dabbling in a little (or a lot of) seed sowing so I thought I’d put in my two cents worth on sowing media.
There seems to be so much mystery surrounding this, and I certainly remember as a novice, wading through acres of information on what type of mix was the best medium for sowing seeds. I remember looking at lots of trials, comparing different types of proprietary seed compost, but in the end, I used whatever was available to me at my local garden centre - I wasn’t about to travel to go and get a particular seed sowing mix. Equally I wasn’t mad keen on mixing any more than a couple of different ‘ingredients’ in order to get the perfect mix. So, here is what has worked for me over the years, and I hope it goes some way to de-mystifying the subject.
One more time: The following suggestions are just what have worked for me in the time I have been sowing seeds - this is in no way an exhaustive list.
Before we start - some seed sowing essentials..
Seeds need a free-draining, nutrient-poor, humid environment to germinate. The texture of any compost or medium needs to be fine - no big lumps but not too fine so as to prevent oxygen from getting in. It’s a balance. For any seed sowing, your best friend will always be horticultural grit or perlite, both to cover seeds with and to mix with your compost. I like perlite because it’s light, but grit is great too.
Peat free multi-purpose compost
This is a perfectly good option for sowing seeds, and some people use it neat with great results. There are loads to choose from, but I always cut it half and half with horticultural grit or perlite, in order to lighten the mix. I also sieve out any lumps and ‘bits’. Imagine you are a tiny seed trying to put down a root; you don’t want to be wending your way around big bits of bark in order to anchor yourself, and access air, water and nutrients. In order to give your seeds the best start, make it easy for them by giving them fine, crumbly, gritty compost.
I have just started using these and I LOVE them. They are basically little pod of coir (coconut fibre) wrapped in a compostable membrane. You pop them in water for a few moments and they expand into perfect little cells which you then sow into direct. They are so easy to use and so far I’ve had 100% germination from them for my tomatoes, peppers and parsley. They need some kind of ‘tray’ so they don’t fall over, and you need to keep a keen eye on them to make sure the coir doesn’t dry out, but this is far and away the most convenient seed sowing method I’ve come across, principally because it is VIRTUALLY MESS-FREE. Yes, you can do this in your kitchen (and let’s face it, most of us are sowing seed in our kitchens) without lugging about loads of dirt…you don’t even get your hands dirty. One word of warning though, make sure the pellets you buy are coir, as there is a big market in jiffy 7’s made out of peat. Using peat in your garden is unsustainable and plain wrong, so go for the coir ones.
I would never have used vermiculite to start seeds, except out of convenience. I wanted to sow something and had run out of compost or grit or something. I noticed an old bag of vermiculite and used that instead. The seeds really really loved it. This is a really great seed sowing medium. It is free draining whilst at the same time holding just enough moisture to provide your seeds with a near-perfect environment. It’s expensive though, and quite distinctive-looking, so it’s not something I would use a lot of, as I always tip my used seed compost over my garden. Recommended for sowing on a very small scale though.
Proprietary seed and cuttings compost.
These are bags of compost sold specifically for seed sowing and taking cuttings. They usually have a higher drainage level (although never quite high enough I find) and are slightly finer. Personally, to all these mixes, I would add more grit or perlite, but generally it’s cheaper and easier just to use a peat-free multi-purpose mix as above. Having said this, I have heard rather marvellous things about Dalefoot wool seed compost, so I will be giving that a try soon. Be careful when buying John Innes seed compost - it often contains peat; always read the ingredients.
xx Laetitia
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