Zinnia zone

It’s pretty widely known that zinnias (unlike the cosmos discussed in the post here, for which it’s never mentioned) are best when direct sown.

That’s all well and good where you’ve got the length of season to get away with it, but way down here where that’s not assured (low latitude, and a bit of altitude – bad combo), you’re sorely tempted to stick some seeds in a pot in mid-spring, and protect them from the coldest o’night temperatures to see if you can get a head start.


So far I haven’t made this work for me.  But admittedly, there’s more than just root disturbance issues to get in the way.  This year I sowed the seed early.  I wasn’t to know, of course, that we were going to have a cold spring, and even a cold start to summer, so it turned out that I wasn’t really able to keep the plants moving through the processes of potting up and planting out as smoothly as they really need.

The self-sown zinnias, with an oil jar for size comparison (and to hide the lame surrounds)
The self-sown zinnias, with an oil jar for size comparison (and to hide the lame surrounds)

The literature tells us that they really won’t grow until the temp minimums reach about 10C (which is slightly different to being frost tender, though the distinction is never made) and they don’t like sitting around waiting. This may have been as big a factor in the relative failure of these plants as the inevitable root disturbance upon planting.  Who knows.

The pot sown plants, sown at six to eight weeks earlier, and planted at the same time as the seeds that were direct sown
The pot sown plants, sown at six to eight weeks earlier, and planted at the same time as the seeds that were direct sown

But having sown them in early October and grown them on, I planted them out in early December, and at the same time sowed some seeds directly into the soil around them.  Within about a month, you could barely tell the difference between them size-wise. The direct-sowns quickly took over for size,  while the earlier-sown plants started to flower much sooner.

The direct sown plants just continued to get bigger and fatter, and once flowering finally started, produced much larger flowers.  They also look like they’ve got loads more flower-power in terms of branching power, and therefore more flowers to come. Conditions since planting have continued to favour the self-sown plants – particularly the outrageously hot dry few months we’ve had, and the total lack of water I’ve had to give them.  The total integration of their root systems with the local conditions seems like a great advantage when it gets tough.

But comparisons aside, I’ve really gotta doff my hat to these zinnias and their resilience in the face of relentless heat and absolutely no water.



  1. That’s odd, I’ve only started growing zinnias this year, and my experience was exactly opposite.
    I had a packet of a green flowered zinnia form a nursery, and also my friend gave me some seeds she collected in her own garden. The green ones were the ones I was really looking forward to, just because I like weird plants. Obviously, the green zinnias were given a nice fluffy patch of soil where they could be looked after and watered, and pampered, and I followed the instructions to direct-sow the seed, at the end of November. Not a single one came up. I wouldn’t blame the quality of the seed, because I’d never ever been disappointed with anything else purchased from this nursery.
    The multicoloured zinnias from my friend’s seed germinated very nicely in their tubes in the greenhouse, they were planted out into pretty poor soil some time just before Christmas, were watered once or twice at the start, and that’s it. I was away from home when the first heat-wave hit us this summer. The “garden-sitter” was asked to water only the vegetable garden and the greenhouse, therefore I expected to see just scorched stalks in my zinnia patch upon return. Not a single one of them had even wilted! They keep flowering with a riotous abandon, and, needless to say, I’ll be looking to get more and more of all my favourite colours, and I’m thinking of planting them among grasses, to achieve a delightful meadow look that is virtually zero maintenance. I simply can’t wait for next spring.
    May be the secret is to have one single plant in a tube, to minimise the root disturbance? I had part-filled the tubes with ordinary garden potting mix, then added about a tablespoon of seed raising mix on the top, placed the seed, and sprinkled with more seed raising mix.
    I have to take a disclaimer there: if any of my zinnias get a chance to self-sow, I’m certain they will outperform anything else. There’s this mystery about self sown plants that I can’t quite fathom– they seem to have a wisdom and a strength that is all their own.

    1. I’m not at all surprised with your experience, Adele, for reasons I’ve put in my reply to Catherine. Without a doubt the Zinnia ‘Green Envy’ (what a great plant, and a great name) seed was dodgy. I’ve had trouble with it in the past myself. Guaranteed your friends seed was fresher.
      But of course that says nothing about how successful your transplanting was. All my trusted sources (older books in every case – I’m pre-lamenting the fact that we’ll possibly never see really good stuff written from direct, slow experience ever again) say that they don’t like being transplanted, but that the climate in which all these authors garden dictate that they start them in pots/tubes/peat pots before its warm enough to direct sow. An enforced compromise. And clearly given your experience, and theirs, not that much of a compromise, perhaps.

  2. I completely forgot to sow the zinnia seeds my friend Peter gave me, and reading this has just reminded me that they’re sitting in an old envelope at the side of my kitchen bench. Damn. Too late now! But it reminds me of another friend’s experience of buying 2 similar packets of seed, but from different companies, and sowing them side by side in the garden. “Chalk and cheese” she said, when comparing germination, growth rate and even flower colour between them. But why do you need to start your zinnias early? Do the mature plants succumb to autumn frosts otherwise? Or is it just impatience?

    1. Yep to the frost question. I know its hard to believe, but we only have four frost-free calendar months here in Woodend (actually, if you count from the date of the last frost to the first of the following season, its five months, but given that they finish and start approximately mid-month, I can overstate the case and remain truthful).
      The point is that the season is just too short for many annuals – you just get them going, and they turn to kelp overnight. Only by starting them under cover (which means firmly indoors for me – just sticking them under the verandah or under a tree isn’t nearly enough) can we get enough of a display out of them to make them worthwhile growing.
      I’m not at all surprised about the chalk and cheese experience of your friend. In my case it was the exact same seed. But the sad truth is that there’s a lot of dodgy seed sold here and gardeners (particularly beginners) nearly always blame themselves for the failure.

  3. It took me many years to really like Zinnias, probably because I bought some seedlings years ago from a nursery and the plants looked quite pathetic all summer. Then last year I decided to try some seeds in a new area I’d developed. I literally threw the seeds down in October and very soon the plants were growing like topsy. I had installed irrigation on this area and with a 2 month drought was using it. The Zinnias were incredible, they grew so fast and flowered for months. I was so excited by this I kept buying seed packets and sprinkling them everywhere. I had zinnias flowering from Dec-April. I’ve since ordered different varieties from Lambleys so will be interested to see how these perform. I love their bright, cherry blooms…the only issue I have in Sydney’s wet summers is they do get mildew on the leaves towards the end of their flowering period.

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