Contemplating the Cosmos

I ought to be ashamed of my cosmos.  And I am.

When you know how good it can be; how tall, wide, strong – muscular, even  – then you know that this is a pathetic effort, if not quite a total fail.

I love cosmos.  I think I just generally love simple annuals.  But what I’ve come to understand is that while cosmos will produce a flower or two on a mean little upright stem under the very worst of conditions, it’s capable of producing thousands of flowers on a great shrub-like structure under the best conditions.  It’s one of those annuals that’s dead easy to grow, but not so easy to grow really well.  That specification may not be uncommon with annuals, but my experience would suggest that the destiny of any cosmos plant, in particular, is set from a very early age.

I used to be a shocker for buying a punnet of seedlings weeks before I wanted to plant it, or at least delaying for weeks for no good reason, during which time the wretched things would be allowed to dry out until prostrate, only to be re-hydrated just moments before their last gasp.  I admit to being kind of fascinated by this capability – by their resilience.  But what I’ve since come to understand is that this process nearly always triggers responses that leads to a less than happy outcome.  And particularly with cosmos.

This is never so obvious than when you compare the performance of plants sown in pots or trays and eventually planted out to those that self-sow, or are direct-sown into the garden.  The former plants are likely to be in flower much sooner on a much smaller, less branched plant than the latter, which (in reasonable soil, at least), is likely to branch up and build into a solid hemispherical mound before producing its first flower, and then continue to flower heavily for months.   My suspicion is that while they go through the process of being pricked out as seedlings, grown on in pots and transplanted into the garden with apparent ease, any stress during this phase triggers premature flowering.  I’ve found that while the almost inevitable stresses of this process can be minimized, my less-than-perfect attentions aren’t likely to manage it.  These plants were sown too early indoors, then had to sit around in the seed pot for too long while I waited for the weather to warm up enough for them to brave the outdoors.  This is not fatal.  In fact it’s deceptively non-fatal.  The plants look fine, but their fate as mediocre performers is irreversibly set.

Ongoing starvation and/or drought can induce premature flowering in many annuals, as they rush to set seed (if you’ll forgive the implied teleology) before a premature death.  What I’m interested in here is how early in the life of the plant that response is induced. Other tall branching annuals may well show the same thing, but I’ve not seen it as clearly as with cosmos.

On the other hand, annuals which grow from multiple, lax stems that branch out from a basal rosette at ground level, like pansies, violas and petunias seem much more tolerant of neglect earlier on, even of the unforgivable McCoy-neglect, which I’m glad to say I’ve grown out of.  It’s as if, once they find themselves in favourable conditions, even following a pretty rough youth, they seem capable of virtually limitless sprouting from the base, and a perfectly satisfactory display.

All this makes me very cautious about buying punnets of seedlings of the taller branching annuals.  When it comes to cosmos, caution leads to total avoidance.  I want to either have grown them myself, or have them come with a full service history.


  1. Wow – shades of ‘give me the child of 7 and I will show you the man’. You know I’d never thought about my cosmos differences as being caused by ‘childhood deprivation’. The self-sown orange beauties often grow to well over a metre with tens of flower heads. The miserable little white ones I planted form an abused punnet grew into a single stalk with a single flower. I will only grow any of them from sown-in-place seed in future to see if your predictions come true.

    1. That’s exactly what it’s like. How fabulous would it be if there was some financial imperative, somewhere in the world, to sort out all these sorts of triggers? That’ll never happen, so it’s up to we gardeners to speculate, generation after generation..

  2. I do wonder if these failures relate to a compromised root system. Maybe , if at any time during the very early exponential growth phase (even at dicot stage) the plant is stressed, the roots dry out or they touch the sides of the containers , a memory is imposed that influences the growth there after. No amount of later compensational care seems to alter the outcome. The effort is put into flowering as even a few flowers will ensure the next generation. Just a theory as it seems that consistent care of youngsters is an imperative . No attempt to be anthropomorphic!

    1. Love the idea of root-memory. But we’re all just guessing, aren’t we. My imagination sees a stress-induced physiological trigger that predetermines an early shift from vegetative stage to flowering stage – almost like that which happens in biennials over winter. But who knows? Who will ever know?

  3. Thank goodness someone else admits to leaving their poor spontaneous plant buys in the punnet to wither to an agonising death/temporary re-birth.. I’ve lost count of the punnets of basil I’ve sacrificed to the snail colonies in my back yard and the poor frustrated flowery things that are currently getting a squirt of water in their little rock hard punnets before they die. One day I’ll have tilled garden spots ready and waiting before I make a plant purchase (and I may have a pig fly past me on that day too!)

    1. I’m also waiting for that day, Penny. It’s very lovable of us, isn’t it – that we (despite sharing 100 years between us this year), continue to anticipate, with unwavering faith, the arrival of such a day.

  4. I have just been thinking the same thing about my Cosmos, Michael. In November, I had a large patch of self-sown ones from the last season, but there was a gap, so I planted a punnet of them from the nursery. All the seedlings were about the same height at that stage, but now, the nursery ones are about 30cm tall with one flower on each plant, whereas the self-sown ones are heading for shrub status and full of flowers.

    1. A perfect illustration. Same growing conditions. Different early upbringing.

  5. I had just been out inspecting my cosmos seedlings when I read your post and, depressingly, they look pretty much the same as you have described. Ever the gardening optimist I can only wait for them to undergo some sort of late summer resurrection and admire the rampaging sweet peas instead!

    1. I’m beginning to suspect that optimism and a love of gardening are genetically linked.

  6. I understand what you’re saying about transplanting punnet stock and am always amazed that carrot seedlings are supplied and purchased by the unwary. Perhaps the key to buying and planting punnet seedlings is to buy them small before the roots are tangled with each other and thus tear when separating them.
    But I have to say that this year’s cosmos – self seeded – are making a very poor show in my garden this year and am heartened to hear others are having the same experience. Of course, it’s the weather…!

    1. I know!!! Carrots! The rule of thumb, generally, is that tap-rooted stuff is difficult to transplant without substantial compromise, whether thats carrots or poppies. I’ve managed OK with poppies over the years, but I’ve never tried, and don’t intend trying (though having made that statement so emphatically, I can feel a weakening) carrots.
      I agree with your point about buying punnetted seedlings small, but still maintain that the inevitable shock is fully recoverable in some species, but silently and subtley damaging in others. Cosmos is of the latter category. I’d love to know of others.

  7. I planted (red) cosmos seeds from Diggers. Then potted them on into a double laundry trough to grow on, away from dogs/kids. There they stayed and are now 2 meters tall from the soil surface with magenta colored flowers. Wish they were in the garden however they add a certain eccentricity to the view immediately out of the window, waving about high above their trough. Julie

    1. I notice that red is – quite correctly – in parentheses. Wish there was such a thing. They’re pink, as you discovered. A deep rich pink maybe, but pink nonetheless

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