How to grow chrysanthemums for magical late season colour
It’s easy to grow chrysanthemums.
And they’ll add brilliant late-season colour. When the rest of your garden is collapsing gently into the beginnings of winter, chrysanthemums will carry on blooming.
They come in a wide range of colours and styles, from demure daisy types to vibrant swirls of outrageousness.
So I asked Dan Cooper of the online gardening shop Dan Cooper Garden for his tips on growing chrysanthemums.
(To avoid confusion, I should add that Dan doesn’t sell chrysanthemums on Dan Cooper Garden. He sells quality garden tools, accessories and furniture, plus delightful gardening themed gifts and Christmas decorations.
But he loves colourful, dramatic flowers and his Frustrated Gardener blog has become famous for its glorious accounts of tulips, dahlias and exotic planting.)
If you prefer to watch a video on how to grow chrysanthemums, see the interview with Dan Cooper here on YouTube.
Will chrysanthemums come back?
There’s a difference between florists’ chrysanthemums and the hardy chrysanthemums that grow in our gardens. Dan thinks that people have been put off growing chrysanthemums because of the confusion.
Florists’ chrysanthemums are usually grown in greenhouses, in pots. They need special treatment to ensure they flower at the right time or have big showy flowers. If you planted florists’ chrysanthemums in your garden, they wouldn’t come back.
But there are lots of hardy chrysanthemums which are like any other perennial in the garden. Although different varieties vary, many of these chrysanthemums can survive winter temperatures of minus 10C/14F or even much colder.
And if your winters are too harsh, you can lift and store them like dahlias and cannas.
Dan suggests you look for Korean, Rubellum or Hardy Spray chrysanthemum varieties. If whether it’s Korean or Rubellum etc isn’t specified, you can check the label for hardiness or find it in the information from the seller.
How to care for chrysanthemums
Start to grow chrysanthemums by getting hardy chrysanthemum cuttings in mid-spring. ‘You can buy them or get cuttings from friends,’ Dan says. Over the years he has expanded his chrysanthemum collection by trying out different varieties, then taking cuttings from the ones that do best.
Your chrysanthemum cutting will be about 4″/10cm when it arrives. Pot it up into a 9cm pot immediately. This gives it a chance to develop a good rootball before you plant it outside in the ground. Keep it in a light, cool, frost-free place.
In 2-3 weeks, it should have more than doubled in size. At this stage, Dan advises you to ‘pinch it out’, also known as ‘pinching back’.
How to pinch out chrysanthemums
‘Pinching out’ means cutting the top of the plant off, just above a leaf node. You’ll reduce the height by one third to a half, leaving perhaps only 4 or 5 leaves below the cut.
The plant will then send out both side shoots and root shoots. It will grow more bushy and sturdy. You’ll also ultimately get more flowers, although they may be slightly smaller. People who grow chrysanthemums as show flowers want huge blooms, so they don’t pinch them out.
How to plant chrysanthemums
You can plant chrysanthemums once the rootball has grown big enough to fill the pot. You’ll see little roots coming out of the bottom of the pot. Or you can slide the pot off to check.
Before planting, ‘harden the chrysanthemums off’. This means putting them outside for two hours on the first day, then leaving them outside for twice as long the following day. Increase the time again on the third day, and so on for around a week. This makes a big difference to how the plants flourish.
Dan suggests you add some compost, manure or blood-fish-and-bone to the planting hole, although he says ‘chrysanthemums don’t need anything special.’
If you have a dry, hot summer, they’ll need some watering, but Dan says they are generally resilient and drought-tolerant once established. ‘And because they flower late, they’re not trying to flower in a summer heat wave or drought, so they’ll be less affected.’
Stake or support chrysanthemums – start early!
The only other job you need to do when you grow chrysanthemums is to stake or support them. Dan recommends you do this in early or midsummer. He usually uses a single stake, then ties the plant with string. He says you can also use the metal hoop supports or any other support system you would use for perennials.
How to look after chrysanthemums in winter
Some chrysanthemums can survive really quite harsh winters in the ground. Dan says they really don’t like getting too wet, because they can rot. So if you rarely go below minus 10C/14F, you’ll probably be fine with leaving your chrysanthemums in the ground, unless you have heavy rainfall. Generally, it’s rare for UK winters to go below minus 6C/21F unless you live in the North and on much higher ground.
Different chrysanthemum varieties survive very different winter temperatures. When I was checking the hardiness of various chrysanthemums for this post, I came across chrysanthemums that apparently can go down to minus 26C/minus 15F and others that wouldn’t survive more than one night of hard frost. So you’ll have to check each variety separately and accept a certain amount of trial and error.
Dan cuts his chrysanthemums back to around 6″/15cm. He then adds a layer of garden compost or well rotted manure around the roots to help protect them. (It also feeds the soil for next year).
‘But I don’t cover the plant with compost,’ he says. ‘I find that leads to rot.’
How to lift and store chrysanthemums for winter
If your winters are regularly very harsh, then you can lift and store chrysanthemums as you would dahlias. Dan cuts them back to around 3″/8cm and digs them up. He trims the roots a little and plants them in a pot. He then keeps the pots in a cool but light place. ‘That’s the only difference between over-wintering dahlias and over-wintering chrysanthemums,’ he says. ‘Dahlias are kept in the dark over winter, while you keep chrysanthemums in the light.’
Do chrysanthemums grow well in pots?
Yes, chrysanthemums grow well in pots. Dan says that professional growers often grow them entirely in pots, because they can be moved inside more easily as winter approaches.
At Country Lane Flowers, Sue Oriel grows her Chrysanthemum ‘Seaton’s Galaxy’ in pots for exactly this reason. Seaton’s Galaxy is potentially hardy down to about minus 5C/21F, but Sue prefers to move them into her greenhouse before any hint of frosts.
Country Lane Flowers grow all their flowers in their own gardens, so although they sell flowers for bouquets and events, the way they grow them is much closer to the home gardener than to many professional flower growers.
What plants grow well with chrysanthemums?
Dan says that it looks good to grow chrysanthemums with grasses. There’s a good contrast of shape and form, and ornamental grasses are at the best in autumn too.
Other good plants include dahlias and salvias, both brilliant for late season flowering. To find out how to grow salvias, see this interview with the UK’s leading salvia expert. And for everything you need to know about dahlias, see our interview with Steven Edney.
More about Dan Cooper Garden
Dan set up Dan Cooper Garden after the success of his Frustrated Gardener blog. He’d spent many years working in retail, most recently as head of Christmas for a famous UK store chain. So he wanted to combine gardening advice and good gardening tools, accessories and clothing – and of course, with his ‘Christmas hat’ on – gifts. He also has a delightful collection of gardening themed Christmas decorations.