Seed Compost

[plantmark]

I am about to start my first serious growing season on my new plot but I am concerned about the reported poor quality of retail seed compost and losing valuable growing time as a result. I have some old horse manure with no bedding mixed in which I would like to try but I am concerned that rain may have washed the nutrients through.
I am considering trying with 10% vermiculite. I would appreciate some feedback.

[peat]

Hi Plantmark Seed compost needs very little nutrition in it so peat mixed 50/50 with vermiculite or perlite would do well. You can add the compost to make it into a potting compost. Also add some blood fish and bone.

[Stringfellow]

Hi. Seaweed meal, rock dust and wood ash are other possible additions; in fairly small amounts in relation your compost. I’ve just purchased 125L of B&Q Verve multi-purpose compost following Charles rec’ (from trials run for Which? magazine): £6.50 ish! Haven’t tried it yet but it looks like good stuff and at that price it’s hard to go wrong. I’ll add the aforementioned for good measure and see how it goes; fingers crossed. Good luck.

[plantmark]

Thank you for replies. As seeds require very little nutrient, what would be the reason for the poor germination of seed in some compost in trials undertaken by Charles?

[charles]

Good question! and mostly it is because the seed is poor, probably old.
Germination itself should not be affected by the compost unless it is hugely rich in nutrients, which is unlikely.

But after germination, poor composts cause weak or pale growth of seedlings which may stay alive for a long time, but put on little growth.

[plantmark]

But for example in your trials March 2015 with Cress and Spinach your trial suggests poor germination is due to compost? Initial germination in Viridor is certainly much better.

[charles]

You are right and I say in the post that I think “the West Riding compost is a little rich and/or dense for seeds of lettuce, spinach and beetroot. But cabbage, dill and coriander have come up fine”.
Funnily enough my later sowings of spinach, beetroot & lettuce in the same W Riding compost came up fine. So it may have been more to do with drainage as early sowings sit for longer in high levels of moisture. My trays were over a humid hotbed and that can be tricky in February.
Hence adding vermiculite, sand etc is a good plan, for sowing only.

[plantmark]

Thank you very much.

[Author]

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