Dahlias are beloved for their stunning diversity of colors shapes and sizes. But when is the optimal time to sow dahlia seeds to get these spectacular blooms in your garden? Here is a complete guide to understanding when and how to plant dahlia seeds for success.
An Overview of Dahlia Seed Germination
Before diving into planting times, it’s helpful to understand some basics about dahlia seed starting:
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Dahlia seeds have relatively low germination rates, typically 30-75%.
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They take 1-2 weeks to germinate after planting Germination is sporadic over this time,
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Seeds need warm soil temperatures around 70°F to germinate well.
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Starting dahlia seeds indoors is recommended. Direct sowing outdoors is difficult.
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Give seedlings 14-16 hours under grow lights or sunlight daily.
Knowing these key facts provides helpful context for determining the best planting time based on conditions in your region.
When to Start Dahlia Seeds Indoors
Dahlia seeds should be started indoors 4-8 weeks before the intended planting date. This gives enough time for the seeds to germinate and seedlings to grow large enough to transplant.
Here are some general indoor starting guidelines based on your zone:
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Zones 3-6 – Start seeds indoors 6-8 weeks before your last expected spring frost date.
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Zones 7-9 – Start seeds indoors 4-6 weeks before your average last frost date.
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Zones 10-11 – Start seeds in late winter, 8-10 weeks before your spring planting timeframe.
You may want to begin on the earlier side of these ranges if hoping to get earlier blooms. Just be prepared to provide supplemental lighting and warmth.
Transplanting Dahlia Seedlings Outdoors
The ideal window for moving dahlia seedlings into the garden is typically 3-4 weeks after the last average spring frost date for your area.
Some guidelines for transplanting seeded dahlias outside include:
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Harden off seedlings for 7-10 days first to transition them to outdoor conditions.
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Wait until nighttime temperatures remain above 50°F consistently.
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Plant in full sun in fertile, well-drained soil.
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Space plants 12-18 inches apart in rows or clusters.
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Provide support for stems immediately after transplanting.
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Pinch out the center stem once seedlings reach 6 inches tall.
With proper hardening off and spacing, your seedling dahlias should thrive when moved outdoors at the right planting time for your zone.
Direct Sowing Dahlia Seeds Outdoors
Direct sowing dahlia seeds into garden beds is possible but more challenging than starting seeds indoors. Here are some tips if you want to try direct sowing:
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Wait 2-4 weeks after your average last spring frost to sow.
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Choose the warmest, sunniest part of your garden.
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Prepare soil by mixing in extra compost to retain heat.
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Sow seeds 1/4-1/2 inch deep in rows 18-24 inches apart.
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Water gently daily until seeds sprout, which takes 10-15 days outdoors.
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Use row cover to maintain soil warmth and moisture.
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Thin seedlings to 12-18 inches apart.
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Provide support for plants immediately after thinning.
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Pinch out center stem once seedlings reach 6 inches.
Even when direct sown, be prepared to protect young dahlia seedlings from any late frosts with coverings as needed.
Fall Planting of Dahlia Seeds
In frost-free climates (zones 9-11), dahlia seeds can be planted in late summer or early autumn to produce winter and early spring blooms. Follow these fall planting guidelines:
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Sow seeds 8-10 weeks before first expected fall frost.
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Choose warm, protected planting sites against south-facing walls or structures.
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Use cloches, cold frames, or mini-hoop houses over seeded areas for extra cold protection.
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Transplant seedlings to protected areas of the garden once they reach 6 inches tall.
With proper timing and protection from cooler weather, you can enjoy unique winter-blooming dahlias from seeds planted in the fall.
Adjusting for Your Microclimate
Always take your specific garden microclimate into account when deciding planting times. Gardens in cooler pockets or zones should wait a week or two longer when scheduling both seed starting and transplanting dates.
Likewise, warmer sites can often safely move up timelines by a week or two for earlier blooms. Pay attention to weather patterns in your area, and adjust dates accordingly for planting success.
Get Ready to Plant Dahlia Seeds!
One of the joys of starting dahlias from seed is discovering the variety of colors and forms that develop from your planting. Just be sure to provide warm growing conditions, consistent moisture, and protection from frost when starting and transplanting dahlia seeds.
With the right timing for your climate, you’ll soon be rewarded with vibrant, diverse blooms unlike any other flower. So get your seeds and supplies ready to plant dahlias at the perfect time this season!
What is the difference in growing dahlias from seed vs dahlia tubers?
Traditionally people have multiplied their dahlia tuber stock by dividing their dahlia tubers. This method produces new plants that are identical to the parent plant or “mother tuber. ” Growing dahlias from seed is very different from growing dahlias from tubers. If you grow dahlias from seeds, no two plants will ever be the same! That’s right, when you grow dahlia flower seeds, you make a new kind of dahlias that has never been grown before.
When you leave a dahlia flower on the plant, it will eventually go to seed. The flower head turns into a seed pod that gives rise to seeds that you can plant again the following year. Each seed contains it’s own DNA and will grow a new and unique variety. Usually, these seed pods are picked at the end of the growing season, when the seed heads are fully grown and ready to produce ripe seeds. Then after harvesting the seeds, you store them over winter and grow them the next spring.
Dahlia flower seeds get their genes from both the parent plant and the bees that pollinate them. Yes, bees and other garden pollinators really do have a big say in what kinds of plants your dahlia seeds will grow. Bees move pollen from one dahlia plant to the next, and in the process, they change the seeds’ genes. Most open pollinated dahlia seeds will grow single or semi-double blooms with an open-center. To improve their chances of getting a fully double dahlia, many breeders get rid of open-centered dahlias or hand-pollinate their dahlias.
There are some amazing dahlia breeders like Kristine Albrech of Santa Cruz Dahlias who specialize in dahlia breeding. Kristine focuses on hybridizing new dahlia varieties from seed. If you are interested in learning more about breeding dahlias, you should check out Kristine’s book.
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How To Plant & Grow Dahlias From Seed
Once you decide to grow dahlias from seed, you will want to start your dahlia seeds indoors. Start your seeds indoors 6-8 weeks prior to your last frost date. You will have enough time for your dahlia flower seeds to grow so that they can bloom in the summer. Dahlias will bloom until your first frost. It takes about 100-120 days for the seeds to produce flowers.
There are several ways you can get your dahlias seeds to germinate. Dahlia seeds have pretty poor germination rates with 20-80% germinating. The most reliable way for getting your dahlia seeds to germinate is with paper towels. The other method involves direct seeding into cell plugs. For best results, I recommend germinating your seeds with paper towels.
How To Grow Dahlias From Seed
FAQ
What month do you sow dahlia seeds?
Are dahlias hard to grow from seed?
Can you plant dahlia seeds straight in the ground?
When should I start dahlia seeds indoors?
How do you grow dahlias from seed?
To grow Dahlias from seed, start by sowing them indoors 6-8 weeks before the last expected frost. Use a seed tray with well-draining soil and keep it moist but not waterlogged. Once seedlings have at least two leaf sets, transplant them into individual pots. Move outdoors after the danger of frost has passed.
How do you plant a dahlia in the winter?
Sow in flats or trays indoors, 4-5 weeks before the final frost date of the Spring. Transplant outdoors after the threat of frost, when soil temperatures are consistently 65-70°F. Choose a Full Sun location with well-draining, low nitrogen soil. Dahlia seeds require light to germinate, so be careful not to cover them when planting.
When should I plant dahlia seeds?
When growing dahlias from seed, you want to plant dahlia seeds indoors about 6-8 weeks prior to your last frost date. If you do not know your growing zone’s last frost date, you can find it here. This will give your dahlia seeds time to start growing and to be ready to plant outside.
How long do dahlia seeds take to grow?
This will give your dahlia flower seeds enough time to get growing so that they can flower in the summer months. Dahlias will bloom until your first frost. It takes about 100-120 days for the seeds to produce flowers. There are several ways you can get your dahlias seeds to germinate.
