Magic Dahlias: Creating your own unique flower - Gardening with Brendan

The vast majority of people grow dahlias from tubers bought as bare roots or in pots at garden centres or online. There’s no shortage of variety when it comes to colours, size and flower shape with open centred single petal, pompom, cactus, star, collarette, tall and dwarf varieties to name just a few. If you want to know what colour, size and shape your dahlia will be, then tubers are the way to go.

But did you know dahlias – native to Mexico and Guatemala – are extremely easy to grow from seed? In fact, they are one of the easiest plants to germinate and need no special treatment. And the fascinating part about dahlias is that from one seed head of one plant you could get numerous different colours, shapes and sizes.

This is because unlike most plants, which have two pairs of chromosomes, dahlias are octoploids, meaning they have eight pairs and 64 in total compared to 28 in most other plants. This results in incredible diversity when it comes to growing them from pollinated seeds and if you have a few dahlias in the garden, or your neighbours have some too, and you collect the seeds to grow the next year then the chances are you are going to end up with some unique variations.

Last year I only managed to get two dahlias to flower from bare roots. One of the drawbacks of dahlias from seed or tuber is that the tender young growth is an absolute magnet for snails and slugs. The four others I planted in the ground were devoured within days, while the two survivors grown in pots were a yellow star-shaped one and a giant pompom-headed red and white one.

I took seeds from the yellow dahlia last autumn and planted them one centimetre deep in small pots of compost in February. I have now ended up with over 20 plants and a few more from shop-bought dwarf dahlia seeds.

With a bit of light they have grown rapidly indoors on windowsills and some are really tall and fine leaved while others are sturdy and squat.

There’s at least five distinct variations and all are thriving. While they are not frost tolerant I’ve also taken a risk and put some outside in pots sheltered by a porch and they are really taking off.

If there is a hard frost forecast I’ll move them into the greenhouse overnight just to be on the safe side.

The beauty of starting them early is that most slugs and snails are still dormant and the plants have a better chance of growing to maturity, by which stage they are far less attractive to them.

I’ve also pinched the top growth off all of them to encourage bushier plants after they had around four sets of true leaves.

When you do this the side shoots take over and you get a lot more flowers in the summer.

If you don’t pinch them, dahlias will grow one thick woody main stem with less branching and less flowers.

With limited dahlias last year, I’m not sure if I’ll get much variety, but chances are at least some of them will be very different from the mother plant.

Best of all with dahlias from seed, if you do manage to a unique flower, you get to name it. As a perennial, you can also then save the tubers and regrow it next year, or take cuttings and multiply it to get more carbon copies, as cuttings and tubers will be identical to the original plant, unlike seeds.

Or you can just keep on collecting seeds each year and create more and more magical, pot luck dahlias unique to you and your garden.