Dahlias are stunning flowering plants that add a burst of color and elegance to any garden. While they are commonly propagated from tubers, growing dahlias from seed can be a rewarding and cost-effective way to introduce unique varieties to your garden.
In this blog post, we will walk you through the process of growing dahlias from seed.
Materials Needed:
- Dahlia seeds
- Seed trays or pots with drainage holes
- High-quality seed starting mix
- Vermiculite
- Watering can, spray bottle, or hose with mister attachment
- Clear plastic covers or plastic wrap (for the paper towel method)
- Labels for identifying seed varieties (optional)
- Grow lights (optional, but helpful for early growth)
Step 1: Seed Selection
Choose dahlias seeds from reputable suppliers, or collect from your own dahlias at the end of the season.
Method One: Seedling Tray or Pot Method
Step 2: Seed Starting Mix
Fill your seed trays or pots with a well-draining seed starting mix. This mix provides a balanced environment for the seeds to germinate and establish healthy roots.
Don't fill the tray all the way to the top - leave a little lip to act as a resevoir so it is easier to water the trays and not have the water just run off.
Avoid using regular garden soil, as it may be too heavy and retain too much moisture. This can lead to damping off disease or other problems.
Step 3: Sowing the Seeds
Dahlia seeds are best sown indoors, about 6-8 weeks before the last frost date in your area.
I aim to plant out my seedlings in mid-October to early November which means I don't start my seeds until early September. Dahlias grow better under longer day conditions so there's not much point starting them early if you aren't using grow lights.
Plant the seeds on their sides about 10mm deep.
It can be easier to part fill the tray, sow the seeds, then add a little more seed raising mix on top.
I always put a thin layer of vermiculite over the top. This can help to retain even moisture on the seedling tray.
Step 4: Watering
After sowing the seeds, gently water the trays or pots to ensure the seed starting mix is moist but not waterlogged. You can use a watering can or a spray bottle to water the seeds, preventing them from being disturbed. If you have a mister setting on your hose this can also be an easy way to water until you see shoots - then you can switch to sprinkler.
You will want to keep he trays damp but not wet. Too wet and the seeds can rot. Too dry and they may not sprout.
Continue watering after germination.
Step 5: Keep Warm and Light
Using Seed Trays Place the seed trays in a warm and brightly lit area. A bright bathroom is ideal, or a small greenhouse outside. Keep the temperature around 18-21°C for optimal germination.
Make sure to water the trays regularly to maintain consistent moisture levels. Germination should occur within a few days.
As soon as the seedlings emerge, they will need plenty of light to grow strong. If you don't have access to sufficient natural light, consider using grow lights to provide 12-16 hours of light per day.
Step 6: Transplanting
When the seedlings have developed several sets of true leaves and the risk of frost has passed, it's time to transplant them to their final growing location. Choose a sunny spot in your garden with well-draining soil.
If the seeds have been started entirely inside they may need to be hardened off before planting. Over a few days put them outside in a protected spot for a little while before bringing them back in, increasing the time they are left outside each day.
This will help them acclimatise to being outside and reduce shock when they make their way outside.
Plant them to the same depth they were in their pots.
Spacing for seedlings is variable. If you want them to grow the entire season plant them at least 40cm apart (or the spacing you prefer for your dahlias).
If you are planning a breeding program and will be thinning out your unsuccessful seedlings as they bloom you can plant them much closer.
Step 8: Grow and Enjoy
Your seedling babies may need some protection from pests (especially slugs and snails) so use your method of choice.
Unlike tubers, seedlings will need watering from when they are planted so ensure moisture levels are sufficient - especially if you aren't getting any rain.
Dahlias are hungry plants and seedlings don't have a food reserve like tubers. You might consider giving them a foliar feed, or other fertiliser, to help give them a boost. I like to use neutrog products, Charlie Carp, and Powerfeed.
Alternative Germination Method - Using Paper Towel Method
Alternatively, you can germinate dahlia seeds using the paper towel method.
Moisten a paper towel, wring out excess water, and place the seeds on one half of the towel.
Fold the towel over the seeds and place it inside a clear plastic bag or cover with plastic wrap.
Keep the bag or wrap in a warm location, checking the moisture regularly and ensuring the towel remains damp.
Once the seeds sprout, carefully transfer them to individual pots or into a seedling tray with the seedling roots facing downwards.
Using a skewer to make a little hole that the seedling can slide into may be helpful. Be sure to water well after tranplant/potting up.
Allow to grow on as in steps above and plant out after danger of frost has passed.
Alternative Method - Direct Sowing
If you don't want to bother with the hassle of starting seeds indoors you can direct sow your dahlia seeds.
It is best to wait until all danger of frost has passed and the soil has warmed up.
I direct sow around the same time as I plant my tubers - early November.
Sow in position about 10mm deep and keep moist until germination.
Newly germinated seedlings are very tempting to pests so be sure to have a management plan in place.
*I will update this post with pictures as I start my seeds this year