Top Tips for Seed Propagation - March in the Lewis Cottage Garden

Mar 27, 2023

For expert gardener Richard Orton March is the start of the gardening year. Now is the time to put down the seed catalogues, get out into the greenhouse or conservatory and begin, what is for him, one of the greatest joys of gardening - seed propagation. Here he shares some of his top tips to maximise your chances of successful germination.

Even after all these years of growing vegetables and flowers from seed, it never ceases to amaze me how, what sometimes can seem no more than a handful of dust, sown onto fresh compost, can grow into something either quite beautiful to behold or delicious to eat with little more than the application of heat, light and a little water. Of course, it isn’t always quite so straightforward as that but essentially that’s all that is required and no one should be discouraged from trying.

Those of us of a certain age will perhaps remember growing mustard cress on wet kitchen paper or in eggshells at home or setting broad and runner beans in a jam jar with blotting paper in order to see how the seed germinate and grow towards the light; even attempting to grow carrots from carrot tops (how does that happen?). Whatever the route into “growing your own”, the fascination never leaves you and it’s great simple family fun.

As we gain in experience, we realise that there are certain things we can do to maximise success and minimise disappointment and failure. The greatest threat to success is a fungal condition called damping off which is encouraged by damp, overcrowded conditions and poor ventilation.

Here are a few, easy to follow tips to help avoid the spread of this potentially devastating condition.

‍Wash your pots & propagators Microscopic fungi can survive on used pots and seed trays. Washing equipment will help to remove most of the fungal spores and minimise the risk of infection. Soak pots and trays overnight in buckets of water containing a solution of horticultural disinfectant. Scrub and rinse with clean water.

Fresh compost Fungal spores love old compost too, so don’t be tempted to sow seeds in left over compost from last year.
Perlite and grit Improve the drainage and aeration of compost at the surface by adding equal amounts of perlite or coarse grit. This helps reduce moisture and humidity levels, which encourage the germination of fungi spores that cause damping off.
Modular trays v seed trays I have found over the years that sowing seed (especially the larger types) into modular type trays reduces the spread of fungal outbreaks by creating little pockets of compost that, in turn contain any fungal outbreaks and helps limit the spread. Not only that but it also helps the pricking out process by disturbing the root systems as little as possible.
Vermiculite Seeds need light to germinate and using vermiculite rather than compost to cover your seed will aid germination enormously. It also acts as a layer of insulation too, adding to your seeds’ chances of successful germination. Sow your seeds on top of the compost then cover with a fine layer of vermiculite.
Water from below Stand sown seed trays or pots in a bowl or bucket filled with 2.5cm of water. Leave in place for about 10 minutes. This will allow water to soak up from the bottom to moisten the compost, rather than soaking the surface where fungal spores tend to thrive.
Open propagator vents Make sure to ventilate propagators to prevent excess humidity building up, encouraging fungal growth. Open vents during the day (or take covers off if they have no vents) and close at night to retain warmth. Use a cloth to wipe out the condensation from the inside of the propagator cover.
‍Don’t use rainwater to water your emerging seedlings. I know it sounds contrary, but rainwater can contain fungal spores and after all the hard work of washing pots and trays and using all the right equipment it would be such a shame to fall at the last fence.

Good luck!