The cosmos sowed at the end of Feb (2 seeds to a 7 cm pot) are now looking fairly robust and will soon be potted on to individual 1.5ltrs pots.
Once there, they will continue to grow, and be pinched out after 3 sets of true leaves have formed. I say that, but the reality is I probably won’t get round to them all.. but thats the plan.
So what are some of the issues in terms of growing cosmos. Well oversowing in a seed tray can be a pain. So if you get a pack of seeds the inclination is sometimes to sow them all far to closely which can be a real pain in terms of pricking Its why I either sow a couple in a small pot, or even 1 seed per seed tray cell as below. (Each seed is in its own small cell that makes it easy to punish out and pot on).
Now of course many people may be having issue in terms of getting seeds to germinate – not because its the viability of the seeds, but because of the compost they are using. Some will use a multipurpose which is fine (to an extent) however some can really be rich in terms of feed included which isnt ideal for germinating seeds in my experience.
Then there is the different that will have to be faced when using peat free. Now for me, not all peat free composts are appropriate for growing seeds in. In fact some, for me, will lead to failure.
I can only speak for what I use and what works for the plants I grow. I use Melcourt Sylvagrow, and sometimes the version with added John Innes.
What every grower may have to learn, and learn is the right word, is how to grow with what is a possibly a new growing medium. This includes your watering regime. You can often overwater peat free as often it doesn’t look wet, but is, This can lead to seeds rotting.. and you then thing the seeds are at fault, but its your watering regime.
When sow seeds, I don’t have to continually water them in order to get germination on the whole. Sometimes “too much love” ends up killing what you are wanting to grow. So just pushing your finger in is often a good test as to how wet your compost is.
Moving forward, watering with peat free (or certainly the versions I use) takes place more often but you often aren’t watering as much in each session. Thats because peat free often cant hold as much water.. but again it depends on the type of growing medium you are using.
Hopefully this provides a few pointers , but feel free to comment below, and obviously check out our little seed shop https://britishcosmos.sumupstore.com
British Hollyhocks and Cosmos Bipinnatus 
Hello. Great work Jonathan.
Novice starter here. Annual seeds that you plant on in the ground, after the season – do you “clear it” what do you do? Do they self seed?
LikeLike
Annuals and indeed perennials can self seed for sure. So if you take the example of a hollyhock…. One plant could produce 3000 seeds.. purely so a new plant is established the following year… thats what plants want to do. So yo can collect the seed if you want to sow them yourselves… or let them self seed – but you know the vast majority of the seeds may get eaten, or not work (thats why they produce so many). WIth cosmos … you can collect the seeds for use the following year.. or let them self seed (which they will even if you think you have collected them all) and then when the first frosts come in Autumn.. could be October, I then remove the plants. And the process starts again the following year with them. Of course with both hollyhocks and cosmos, seeds may not come true – as they will cross pollinate so the new plant may look quite dfferent in terms of colour.
LikeLike