How to Start Breeding Dahlias from Seed
- Jane Westoby
- Mar 20
- 5 min read
Updated: Apr 8
There’s something completely magical about growing dahlias—but breeding your own? That takes it to a whole new level.
In episode 3 of the Blooming Garden Podcast, I chatted with Pam Lyons from The Untamed Garden, a fellow dahlia addict and home breeder based just a few miles from me in Surrey. Together, we dig deep into the joys (and occasional heartbreaks) of breeding dahlias from seed—what to look for, what to avoid, and why it’s not as complicated as you might think.
Whether you’ve just bought your first tubers or you’re already knee-deep in seedlings, this episode will give you practical tips and a little nudge to start experimenting.
Why Breed Dahlias?
Breeding your own dahlias gives you the chance to create something totally unique. Every seed holds possibility—new colours, new shapes, new favourites waiting to be discovered.
Pam puts it beautifully:
“There’s so much joy in growing from seed… and you don’t need perfect isolation or a plan—you just need to start.”
Understanding the Basics
Dahlias are octoploids—meaning they have eight sets of chromosomes, which gives us all those wild, wonderful forms and colours. But it also makes the genetics… well, a bit unpredictable.
“That unpredictability puts some people off,” Pam says, “but it’s also what makes it exciting.”
You never quite know what you’ll get—but that’s half the fun.
How to Collect Dahlia Seeds
You can hand-pollinate with paintbrushes and organza bags, or you can let the bees do the heavy lifting. Either way, timing is key.
Top tips for seed collection:
Keep cutting blooms early in the season to encourage branching.
From mid-August, start letting a few blooms go to seed.
Pick seed heads before they’re fully papery (especially in the UK’s soggy autumns).
Dry them indoors in jars of water or on trays to finish maturing.
Pam’s top trick? If its a wet Summer/Autumn snip the whole stem like you’re cutting flowers, pop in water, and let the seed head mature in a vase indoors.
Ensure the seeds are fully dried out for a few weeks then store in an envelope until next season when you are ready to sow.
When and how to Sow Dahlia Seeds
Just like tubers and cuttings dahlia seedlings are not hardy so they need to be protected from frost. For this reason it's best not to sow them too early, unless of course you have a large heated greenhouse or a conservatory. You can of course keep then indoors on a windowsill but you need to ensure they do not become leggy and there's a limit to how many windowsills most of us have access to.
If you can bring then indoors overnight and on poor days then 4-6 weeks before your last frost date would be ok. That means that they would potentially be indoors for much of that time, especially in the first few weeks.
They can be started in pots or trays by simply making a small hole with a dibber or your finger, popping the seed in the hole and then covering over. Water well and keep somewhere warm, a propagator is ideal and will speed up germination.
Seeds can also be started on damp tissue paper in a zip lock bag. Check every few days and pot up all the ones which have germinated straight away. Do not be tempted to leave them to grow in the bag as they will not survive the transplanting. Grow on indoors and gradually start to pop then outside on sunny days for a few weeks before planting out after all risk of frost has passed.
Transplanting your Dahlias outside
Do not be tempted to plant out too early - Dahlias will not survive a frost. You can check your last frost date online for your area and if you are in any doubt - you may be in a frost pocket ! Just wait a few more weeks. Just because you see others planting out doesn't mean that you can too. I live near the south coast of England near Southamption, and our last frost date here is around mid April. Just 1 hour up the road where we lived up until 3 years ago in Fleet the last frost date is Mid May! A good 4 weeks later, and if you live in the north of England I'm guessing it's June.
Because of the nature of Dahlias you may find that you have a lot of unfavourable characteristics when growing from seed so the trick is to grow lots and plant them very close together.
They can be planted literally touching each other still in the plastic pots. This will enable lots to be grown in a small space, they will still grow tubers but they will be confined and smaller than they would be if planted in the ground.
Do not pinch them. You want them to produce flowers as quickly as possible so that you can see which ones you want to keep.
Any fuglies that you don't want you can easily pull from the ground together with the pot. Once you have your first flush of flowers you can cut back the stems for more.
By the end of the season they should have all formed some tubers which can be dug and over wintered. Some will be small and may not make it if they are not kept hydrated. So any which you really don't want to lose you can keep in the pot over winter, frost free with a little water every now and again to give them a better chance of survival.
What to Look for When Breeding
Everyone has their non-negotiables—mine’s red. Anything with a hint of scarlet gets pulled. For Pam, bad form is a quick no, as are downward-facing blooms and weak stems.
What we’re both looking for:
Strong, upright stems
Interesting colours (muted, muddy, or romantic tones, not neon brights)
Good vase life and form
Bonus points for unique seed shapes—because yes, seed size often mirrors petal length!
Isolation & Pollination Techniques
From hand-pollinating to bee-assisted breeding, there are lots of ways to encourage the crosses you want:
Grow different forms in separate gardens or areas.
Use natural barriers like hedges or buildings.
Consider tunnels or pollination by flies (if you’re brave!).
The key takeaway? Start simple. Don’t overthink it. Let nature take its course and save seeds from the plants that spark joy.
What You Can Expect
When you grow dahlias from seed, you’ll get a whole spectrum—from wild singles to fluffy doubles, and everything in between. The real magic is in the surprise.
“It’s like raising chickens,” Pam joked. “You shouldn’t name the ones you’re going to cull.”
Some will be beautiful but unusable. Others will be keepers. And once in a while, you’ll strike gold.
Want to Get Started?
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🎧 Listen to the Episode
👉 [Click here to listen to “How to Start Breeding Dahlias from Seed” on your favourite podcast app.]
This is a must-listen if you’re curious about seed saving, obsessed with dahlias, or just want to grow something truly your own this season.
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