Ready to embark on the wild and wonderful journey of dahlia breeding? Growing dahlias from seed is an adventure full of surprises, one-of-a-kind blooms, and—let’s be honest—some quirky oddballs that pollinators will adore. Unlike predictable tubers, dahlia seeds are a genetic lottery: every plant is unique, bringing its own special charm to your garden. Here’s everything you need to know:
P.S. Don’t miss our free printable guide for starting dahlias from seed—download it below. Plus, we’ve included videos of our dahlia seed grow-along for even more insights and inspiration!
Why grow dahlias from seed?
Growing dahlias from seed is more than just gardening—it’s an art form, a science experiment, and a daily surprise rolled into one. Here's why it's worth the effort:
Endless Variety: Each dahlia seed holds the potential to create a flower that is totally unique. If you grow one you love you can name it and even register it with the RHS. How cool is that?
Showstopping blooms: We collect our seeds from specific, isolated, flower forms, to improved the odds of growing your next garden superstar. It's impossible to avoid a few oddballs but that's all part of the fun!
Thrill of the Unknown: Every plant is a surprise and waiting for the first buds to open can become quite addictive. Who knows you might just grow the next Café au Lait.
What You’ll Need
A warm spot, around 18–21°C (65–70°F)—basically, not the fridge!
Light—natural, artificial, or the glow of your good intentions (hint: grow lights work best in the UK?).
A shelf (no need to raid IKEA; any surface will do).
Seed-starting compost
Dahlia seeds (obviously).
Kitchen roll (the trusty hero of this operation).
Cling film, sandwich bags, or a takeaway container (yep, it’s as glamorous as it sounds).
Seed trays with lids.
10 cm (4”) nursery pots.
A watering can (or a recycled milk jug if you’re thrifty).
A balanced organic fertiliser (and maybe a pinch of luck).
How to sow dahlia seeds
Step 1: Get Set Up
Find a warm spot indoors and assemble your seed station. If it’s a bit dark, grab some LED or fluorescent grow lights. Got a spare shelving rack? Perfect. You’re basically running a mini greenhouse now. Dahlia seeds need a head start, so plant them indoors 4–8 weeks before the last frost.
Step 2: The (Kitchen Roll) Magic Method
Here’s where it gets fun:
Tear off a bit of kitchen roll—those perforated half-sheets are genius. Wet 3–4 sheets under the tap, then gently squeeze them out. You’re aiming for “damp,” not “wring it into a bucket.”
Lay the seeds on one side of the damp kitchen roll. Fold the other side over the seeds like a little duvet.
Plop the folded kitchen roll into a sandwich bag, a takeaway container or onto a plate or tray, cover it with cling film, and stick it in a warm room (18–21°C). Too cold? Use a heat mat, but don’t go above 24°C—dahlia seeds are divas and will sulk (rot) if it’s too hot.
Check daily from Day 3 onwards. Sprouting can happen sporadically, so be patient. If the kitchen roll dries out, give it a spritz of water (don’t drown it, though!).
Arrange on damp kitchen roll for germination. 
Dahlia seeds in moist kitchen roll, germinating on a warm window sill.
Step 3: Planting the Little Darlings
Once you spot tiny white roots, it’s time to act. Carefully peel the seedling off the kitchen roll (if it’s stuck, snip the paper around it and plant that too). Pop the sprouted seeds into seed trays filled with moist compost—roots down, obviously! We like to put pencil holes where we plan to place seeds, allowing us to see where we've placed a germinated seeds, as seed trays will fill slowly over the course of 1-2 weeks, as seeds germinate.
Step 4: Keep Them Alive
Here’s where you channel your inner plant whisperer:
Give them light—13 hours a day under grow lights will keep them happy. Position the lights close to the plants, but not so close they get a suntan.
Keep the temperature around 18°C (65°F).
Water sparingly from the bottom, which means placing water in the tray to be soaked up, rather than on top of the soil—think “Goldilocks soil”: not too dry, not too soggy.
Once they’ve grown five sets of leaves, pinch them back to four sets. This makes the plants bushier and gives you more flowers. More flowers = more seeds.
Dahlia seedlings under a grow light. 
Transfer dahlia seedlings to larger pots when roots begin to emerge from the bottom of the seed cells.
Step 5: Moving Out
When the frost has cleared off for good, your dahlias can finally go outside. But don’t throw them straight into the wild! Harden them off first by putting them outside in a shady spot for a week. If the temperature drops below 7°C at night, bring them back inside—they’re not fans of cold snaps.
If they’re getting too big for their pots before the weather warms up, pot them into something larger (4" pots work well) to avoid root issues. Pro tip: some garden centres give away used pots—check their recycling area!
Fertilising and Other Fancy Stuff
Once your dahlias are in their final home (pot or garden), give them a little snack—a balanced organic fertiliser works wonders. Feed them again in July and August to keep them blooming their socks off.
Oh, and don’t forget to deadhead. The more you snip, the more they flower—it’s basically free bouquets for months, then of course, let a few blooms go to seed to feed your growing dahlia addiction.
The Rogue Method: For Bold Gardeners Only
Feeling adventurous? Skip the pampering and plant seeds directly in moist soil indoors. This natural-selection approach lets the strongest seedlings thrive. We have done this and found that a similar amount of seeds germinated to the kitchen roll method. However, this wasted seed cell space on the duds, as dahlias typically have lower germination rates. By starting in kitchen roll, you can save the VIP seating for those that are committed to life in our gardens.
Share Your Untamed Dahlia Journey
Your garden isn’t just a project; it’s a story. We’d love to see how it unfolds!
Show Off: Share your progress and blooms on Instagram @The_Untamed_Garden.
Celebrate Together: It’s not a competition (but okay, maybe just a little).
Let’s flood the world with untamed beauty—one bloom at a time
Got questions, complaints, or a slug-related horror story? We’re here for you—just drop us a message!
— Pam & Claire
FAQ - Your Dahlia Dilemmas Solved
Q: How long do dahlia seeds take to germinate?
A: Most sprout in 2–14 days. If you’re growing double blooms, expect a bit more waiting—it’s worth it!
Q: Can I plant seeds directly outdoors?
Q: When can I plant seedlings outdoors?
Q: When should I plant the seeds in soil?
Q: Why don’t my dahlias look like the seed packet picture?