Re-starting warm sowings

A weird phenomenon is happening with my indoor sowings one species after another: the seedlings would start to elongate excessively right away after germination, just to vanish in a blink of an eye afterwards (exemplified with Minuartia michauxii). Species like Minuartia, Silene, Luetkea and others like them have done the worst; a few more vigorous ones like Campanula alliarifolia and C. glomerata have surviving seedlings that will be pricked out soon.

It is not the regular damping off of seedlings; I had it happening as well over the years, albeit very rarely. You can read in the following post, how to avoid the damping off for indoor sowing: https://www.gardenmyths.com/damping-off-disease-prevention-treatment/#Preventing_Damping_Off_Disease

I started to analyze what’s different than in the previous years. I am using the same method of sowing, clean pots, the same indoor lights (set at the same height) and the room temperature is as usual.

There is only one thing different: the sowing mix! This year, not having my usual around I used a Fafard I recently purchased. I went to look at the bag more closely. My usual sowing media in the last years has been the Miracle Gro or Pro Mix, to which I added vermiculite or perlite. Comparing the two, we can see the ratio of fertilizers the Fafard mix has. Another difference is that it contains coconut husk but that usually improves the mix drainage and aeration and it shouldn’t be a problem.

I see no other explanation for the excessive and rapid elongation of newly germinated seedlings: the excess of nitrogen and the salt concentration in the little sowing pot cause the fast ‘melting’ of the seedlings. When the concentration of fertilizer is too high in a larger pot, it can be washed out and reduced with each watering, but newly germinated seedlings do not need a lot of watering.

I do not want to waste my time investigating further. In Canada, unfortunately, we do not have standards for the bagged sowing and potting soils, anything goes. It is of course also my fault for not watching closely what’s written on the bag. How many people are doing it? You just grab the bag on the way to the check-out.

Newly germinated seedlings, talking mostly perennials for rockery here not tomatoes and petunias, do not actually need any fertilizer for a while. The introduction of a diluted fertilizer is welcomed later after they have grown up a while, or after pricking. What can one do  besides complaining? I sowed again yesterday in Miracle Gro (where seeds still were still available) plus we can learn from my mistake. I will post an update later.

I mentioned before that it is not good to sow a whole pck. of seeds (keep ½ in case ‘accidents’ happen), now I will add the following to the general sowing advice: have a good look at the added fertilizers in the sowing mix and before sowing a whole flat of pots, better do a trial with a few seeds that germinate very fast. Wait a week to see how the seedlings do and only go full blown sowing after that.

To finish on the bright side, the first seeds of Hepatica are starting to germinate (kept outdoors) and Hepatica transsilvanica is starting to bloom :)