Avoid damping off during indoor propagation

If I can offer any tips for indoor propagation on a small scale, it’s do a small number of things to avoid damping off. Damping off is a bunch of fungal diseases that will cause ALL seedlings to die quickly.

I learnt this the hard way, losing trays of seedlings initially which ‘almost’ put me off trying again. Very disheartening but actually very easily avoided by following the below advice:

  1. Only grow when days are long enough – which is likely to be the second week of March or later. Do not, like me, be too eager even when using extra grow lights. More sunlight will make stronger plants quickly.
  2. Avoid overly humid rooms – this sounds counterintuitive to most propagation advice, but personally I would avoid growing seedlings in the bathroom. I found this was the ideal environment for fungal disease and only had success when I moved my Garland 7 propagator into the dry living room. I then controlled humidity locally within the propagator.
  3. Do not overwater – if the compost looks soppy and spongy, too much! I’ve always been guilty of overwatering. Plants need far less than you realise – it’s a careful balance learnt over time.
  4. Use only new seed sowing compost – it will be sterile of disease, getting you off to the best start (beware of bags that look like they’ve been left out in the rain all winter).
  5. Keep air moving – one of the best preventions is keeping the air circulating as this moves fungal spores on, stopping them from getting hold. How you do this is tricky because in early spring, you also need to avoid cold drafts, keeping the temperature consistent. I found that a larger room (our living room) was best. It had some slight natural air movement thanks to the room having a chimney breast and being nearer the front door.
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Jack Wallington

I'm an RHS qualified garden designer living in Clapham, London who loves growing plants and designing with them. Follow me on Twitter.

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