I sowed three varieties of Cosmos seeds

Last Sunday I sowed some Cosmos seeds (three varieties) and was amazed to see them appear within two days. Eight days later and they are already 4-5 inches tall but a couple of them have started to flop. None of them have two sets of leaves yet so can’t be potted on. They are very thin and leggy so I’m not sure they will survive. I think they are too weak to stake yet. Compost has not dried out.

A bit of Googling told me that they get too tall when there is not enough light but they have had plenty of sunlight in the window this week and I regularly turn them around.

I still have some seeds left so if all fails, I shall just sow in position in May but I wanted to be more precise about where I put them.

Anyone sown Cosmos before? Was it successful?

Pity about your lovely Cosmos, Dongle.
I was going to say about the light source, but then saw you already found that out.

In my experience, the trouble with window sills can be twofold.

  1. Depends window sill you are talking about. Is a room you are using all the time, and the lights are on all evening after dark? Otherwise, they do not get enough light if the light source disappears suddenly and they are ind darkness for perhaps 12 hours or more, until the sun comes up again next morning.

  2. Are they behind a net curtain, or up against the glass in full sun?
    Turning the tray is good to stop them bending towards the light, but they bake when the sun is out, and cool rapidly as the sun moves round.
    In other words, you get temperature fluctuations, the gentle warmth they need is not stable.

My guess with yours is, the temperature was too high, and that is what made them germinate so quickly.

I have a packet of Cosmos here at the moment, and it says:

They need a temperature of 15-20 degs, and to keep them moist.
Seedlings usually appear within 14-21 days.
When large enough to handle, transplant seedlings to 2" apart, and grow on on Cooler, but not cold, conditions.

You can plant them direct outside, but they are frost sensitive, so can’t plant till end April - end May to be safe.

Personally, I think if it were me, and mine were not strong enough to support themselves, I would discard them and start again. You have still got 2 - 3 weeks to plant indoors, so don’t give up. :smiley:

I had to google these. At first I just had a picture of the galaxy! They do look very pretty so worth persevering.

Hi Mups

Thanks for you reply.

At the moment, it’s about three or four that have gone awol out of about thirty.

They are in a South facing window which does get sun all day. We do have wooden blinds but I often turn them so that the light is directed at the plants but they are in the bedroom (The cats would probably destroy them otherwise):cry: Obviously that means they are in darkness for hours at night.

From what you say, it’s the temperature that’s more important than the light so I’m not really sure how I can improve on it. Some people say, just throw them in the ground but surely there would be the same problem with darkness at night and temperature changes.

I don’t mind starting again although I would probably buy some more to make sure I have plenty of chances.


I have a packet of these ‘Seashell’ mixed, dongle.

They are the tall ones though (4ft),and there are about 100 seeds in the packet.

They look very pretty with their ‘wavy edged’ petals, but I haven’t got room to grow them. You are most welcome to these seeds if you want?

This is what they are like:

I think to germinate best, they need gentle, constant warmth, rather than very hot for a while, then cool, then hot again.

They would be ok to sow outside, but as I said earlier, not just yet as they frost will kill them.
We have this week with cold nights and possible frosts forecast for a start, so I’d wait until May.

Aw thanks Mups. Don’t worry, we have quite a good garden centre about half a mile away and we will be there this weeks buying something or other I’m sure. thanks for the offer though. :008:

Thanks also for the link. They are lovely looking plants aren’t they. I can’t get my head around how a seed that small could grow to 4-5 ft in one season and flower.

As you know Mups, I am a complete novice when it comes to seeds but prepared to have a go at growing a few things.

Okey Dokey.
If you change your mind, you know where to find me. :smiley:

In the wardrobe? :-p

I love cosmos,it fills spaces,with beauty,I love everything about it,I usually buy it in a pack of 10,well on its way,I may buy some seeds tomorrow from Wilko,have you seen how high some of them grow?

Of course. :lol:

I have grown the smaller Cosmos before, they are nice too.
The ‘Sonata’ strain.
Have a look. I like the yellow ones, third picture down, haven’t tried them yet though.
For real gaudy colours though, see the 4th picture down. :slight_smile:

I first saw them at Rosemoor and thought they were so lovely but still can’t believe they grow so much in one year. So are you saying you can buy them as young plants pauline? I haven’t seen them around here.

So nice aren’t they. I should have said that also have some dwarf ones which seem Ok at the moment. I have increased the light by moving them higher up in the bay window and have started brushing them gently with my hand to see if it thickens them up. I will give them another week or so then will replant if needed. Trouble is, I’m not really sure what I can do differently. :017:

Dongle, loads of places sell plug plants online, plus most garden centres too, but Sarah Raven’s are spectaclular. Have a look here, you’ll love them.

Ha! Yes, thanks Mups, I googled it and came up with the same link. In fact, my seeds are Sarah raven too. Might be an idea if all else fails and I could try something else from seed. I am also growing those little multi-coloured daisy things (forget the name) which seem OK too.

Runner beans soon too. :-p

Hers are really beautiful, aren’t they.

If you do decide on plugs though, best not leave it too long to order, else little ones will have grown o, big. The smaller plugs are cheaper than bigger plants.

Thanks for the advice. I’m off to the garden centre tomorrow to see what they have then will take it from there. x

Good idea to have a look round.
Can I come? :smiley:

Let us know how you get on.

Will do. I will be buy you an imaginary latte and one of their iced Danish pastries. :lol:

If mine get a bit “leggy” I plant them deeper in the pots when potting up. It works sometimes.