Cosmos again!

I have about 40 cosmos seedlings that germinated in Feb... didn’t grow much indoors... but that I then put outside 2 weeks ago!

Only a couple seem to be dying but clearly we’ve had cold nights and despite some warm days, they haven’t appeared to have grown at all! Are these a write off? Should I put them all in the summer house? Or start more indoors?

Temps still drop to 3 or 4 each night where I am!

 

I found threads from last year and see I’m about a month too early for putting these out!!!

Should I bring these in... or just start completely afresh?

Do you think some might survive the next month and go up ok or is the damage already done?

 

Well, not a write off, but they are in big pots and still only pretty small.
IMO, they are too small to be planting out and could easily go another few weeks in those pots.

 

@kriss
The pots used are way too big, I have about 30 in the green house and they are all in 9cm square pots and will probably stay in these pots till they are planted out

 

My Cosmos are in 6 cell trays. I would only put most plants out from the start of May.

 

I start mine off too early every year ... my sowing-diary has loads of crossings out and later date notes but even this year they are more advanced than I would like. They become a nightmare to handle if they are too tall when planting out (never been quite sure about pinching out ... I ought to do half-and-half and compare). But mine are in greenhouse ...

I'm a big fan of a sowing calendar with notes of "when" from previous years - Dates for sow, plant out, first and last Harvest or Flowering and then following years opportunity to improve on previous seasons.

I want mine to flower early ... but Cosmos grow faster than a lot of what I grow.

I don't think your container size is a problem (now that it is done), but putting them in smaller containers - e.g. plug cell modules to start with, then 3" / 9cm pots and only then on to 1L pots if absolutely necessary - makes it much easier to get the watering right. Big pots hold a lot of water and small plants don't drink very much, so very hard for the plant to overcome over watering. The potting-on process also forms a better rootball - instead of the roots going straight to the outside of a big pot they fully populate the one they are in, and then when you pot them on they fill that one too. You may find when planting out your bigger pots that the rootball is not well filled and it falls to bit. Doesn't matter, per se, but there will be some root damage and it will set the plant back.

The cold will also set them back too, which puts stress on their immune system to combat any invaders, and some things go into "survival mode" and take ages to come back out of that - basic instinct to make sure the problem has definitely passed before having-another-go, so yours will probably perform well, but if you planted some more now they would probably overtake them and be bigger and flower earlier. I'd keep what you have got though, if we get a heatwave they will be ahead of any replacements ...

Of course in nature a seedling has to put up with whatever it encounters, but us gardeners are striving to improve on nature and get best possible outcome. I want sooner, bigger, more and tastier

 

The smaller pots I had were really shallow... and as I planted them way too early... I’ve repotted them deeper so had to use those big pots.

So note to self- wait till late March to plant seeds the next time and they won’t be so leggy!!!

move planted more seeds and brought a lot in the smaller pots indoors!

 

Here are my second batch of seedlings. Are these cells good till the plants are 4 or 5 inches and busy?!

 

Nice size,..plenty of space for roots to form and to hold enough moisture,..they wont dry out too quickly.

 

I was always reluctant to pinch out cosmos until last year when I bit the bullet and went for it..Best Cosmos I've ever grown..lovely big bushy plants

 

So the cosmos crop actually looks ok.... some really bush... some lanky but with a healthy number of buds that have been flowering.

how long can I keep some of them in the larger pots? Should I really now aim to get them all planted?

ideally I want to see which are the best before committing them to key places in the garden! There are some roots growing through the bottoms of the pots now as I planted some of these deeper and deeper.

 

Bingo ! I’ve posted about weird looking cosmos tops yesterday, reading this strand I am tempted to simply cut off the top bits and hope the plants develop healthy side shoots ! Brilliant !

 

I think your only down side to that is it's quite late, but tbh I don't think that you have much to lose.
Flowers into late October could be the outcome.

 

Yes, hope so ! These are mine very late last year ! November in fact !