The same cooling weather that is initiating fall color is what finishes the zinnias that bloomed so colorfully through summer. Like tomatoes, they can stay out in the garden until they succumb frost if they continue to perform, and if the space they occupy is not needed for something else. There should be no guilt with replacing them sooner. After all, they are technically warm season annuals.
Some of the more popular types of zinnias are identified as Zinnia elegans or Zinnia violacea. Most are known merely by their variety name. They have been bred so extensively than it is difficult to assign any of them to particular species. Most are susceptible to mildew if crowded or watered from above. They want full sun exposure and rich soil. Seed can be sown immediately after frost.
Zinnias are crazily variable. Some get more than three feet tall. Others are less than a foot tall. They can bloom in every color except blue. Some resemble other types of daisies, with distended centers. Others are as fluffy as African marigolds. Some bloom with small but profuse flowers. Others have fewer but bigger flowers that are wider than three inches. Most are excellent cut flowers.
Tony Tomeo 
Just planted some dwarf, 20cm, bright orange zinnias as a border. Hoping they will last all summer
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They do very well for some. I do not grow them because the few I tried years ago were so susceptible to mildew. Snapdragons do the same. I do not grow them because of rust, but they do very well in other gardens.
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I’ve not grown them in Australia I had reasonable success in NZ but I’m on this cottage/native garden make over obsession at the moment. May regret the change when the hot dry humid weather of summer kicks in….
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Especially since you are away form the garden while traveling. It is not easy to tend to the garden while away.
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That’s why it was all broms and no care plants before, but not so much travel now
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Also – they make excellent, long lasting cut flowers, and the single varieties (not the frilly doubles with a gazillion petals) are very popular with certain butterflies – especially Swallowtails and Monarchs –
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The space for my gardening column is quite limited, which is part of the reason I prefer to discuss simpler and less interesting flowers. This short article is the second part of my gardening column for today. The first part was yesterday. I post them here just as they appear in the newspaper, except cut into two pieces.
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That’s an old time flower that not many people grow around here any more. It was one of my grandmother’s favorites: her zinnies.
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That is sort of the impression that I get. Although, they seem to be getting popular again. In fact, a few flowers of that family were popular over the summer. Rather than marigolds and petunias, there are zinnias, black-eyed Susan, blanket flower, coneflower and tithonia. Tithonia was something that only recently became available here.
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I have some hollyhocks here; another old time favorite.
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Yes, but another that can be susceptible to disease in some spots. It gets rust very badly. I do not know how it can be so easy to grow in more humid regions.
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It does get rust and there are also some kind of bugs that eat the leaves. I can never figure out what’s doing that. Some years they do better than others, but being bi-annual, I always have some blooming.
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Biennial? We do not keep ours around that long.
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Yes, they grow as biennials here. The first year we get short plants, the second year those come up again, get taller and flower. I thought they all grew that way. They always have here.
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That is how they grow naturally. However, no one here keeps their ‘annuals’ for more than one year. Landscape ‘maintenance’ companies can charge more for constantly replacing annual color. Many of what we consider to be annuals are actually biennials or perennials. It seems odd that zinnias would be allowed to regenerate for a second year in your climate, which is not as hospitable as ours is.
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Wait, sorry, evidently I confused you by not explaining well. It’s hollyhocks we have that grow as biennials. Zinnias reseed naturally and produce new plants, or I save seed if I want to control where they grow,
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Well, that makes more sense. Not only do the survive winter better, but some may not even bloom in their first year. They are grown as annuals here, but only because the plants are mature enough to bloom when purchased. I think that they can grow as a perennial, but I have not paid that much attention to them.
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