Hi, Ive started to grown my own flowers this year and too my suprise I actually have seedlings (cosmos flower). However I don’t know how long to leave them in the propagator for and when to transfer them to a bigger pot. Any advice welcome
Yes cosmos are quick to grow early on. Personally I'd start moving some of the bigger seedlings into larger pots. It is beneficial to bury some of the stem to help with leggy growth. This old thread provided good advice
Bouncing on @Astro's comment, it's a very good technique. In my itchiness to do something and get going this winter, I started some seeds off very early. Needless to say, they got leggy (first timer sower mistake) and I used this trick when it was time to pot them on. I now have healthy looking geranium, hollyhock, and dahlia seedlings.
Cosmos from my limited experience so far are quick, I've planted some purity and fizzy white and within 3 days they were all up 100% success. I think they are fairly hardy, last year I direct sowed some in April and they were wonderful. I would start with the tallest, prick out and pot on slightly deeper as described above. They're going to need more room fairly quickly.
Does this same technique apply to other species? (I have Amaranth and Antirrhinum/Snapdragon seedlings which are also a little leggy).
Snapdragons can be burried, also you can also cut them down to their first true leaves and they produce twice the stems. I'd try and get them into cool and bright conditions if they aren't already, they are hardy and it'll stop them getting leggy.
Amaranth I have grown though I'm less sure if they can be burried, they seem a bit more tender earlier on, I could picture them rotting . Perhaps try one and see what happens. I found I had to mollycoddle them until the weather was quite warm otherwise they sulked
The video was helpful, but where he was wrong was pricking them out and holding the stem. When pricking them out you should always hold the leaf, so that you do not damage the stem.
Thanks @SophieK for the video and @Astro for the old thread -- anyone happen to know if this works for "most" seedlings ( ie stem burial up to seed leaves, i know some plants are fine to be buried deeper if need be ) - comment re amaranth noted -- specifically my q is re nasturtium -- should all be dwarf ones ( tom thumb) but I appear to have one seedling in particular that is 4 times the height of the others.... ( maybe it is just a rogue variety seed, was from wilko so not expensive)
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In my itchiness to do something and get going this winter, I started some seeds off very early. Needless to say, they got leggy (first timer sower mistake) and I used this trick when it was time to pot them on. I now have healthy looking geranium, hollyhock, and dahlia seedlings.
This video was useful: https://www.youtube.com/watch?v=hfDgMJyP3ps
Amaranth I have grown though I'm less sure if they can be burried, they seem a bit more tender earlier on, I could picture them rotting . Perhaps try one and see what happens. I found I had to mollycoddle them until the weather was quite warm otherwise they sulked