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Growing Delphiniums from Seed

Growing Delphiniums from seed.

Table of Contents

Why Starting Your Own Seeds Makes Sense

Until I retired, I didn’t even realize how hard it was to buy all the different Delphinium plants I’ve grown for decades myself. Luckily with a lifetime of experience in starting delphiniums from seed, I can share with you what I’ve learned. I’ll take you through each step of the process, from choosing quality seeds to transplanting in the garden bed.

delphiniums in full bloom and grown from seed.When you start plants yourself, you will be able to choose from a much wider selection of delphinium varieties compared to what you might find at the nursery if you even could find any at all. In the long run, starting your own plants from seeds indoors is cheaper than buying plants from a nursery.

Choosing the Right Seeds

The first and most important step is to choose high-quality delphinium seeds. Look for seeds from reputable suppliers to ensure the seeds are fresh and viable. Older seeds may have reduced viability and germination rates. Delphinium seed varieties are diverse. Each type exhibits distinct features, such as flower color, height, and stem strength. Tailoring your choice to your garden’s needs ensures further success. If you know that you are not the type to get out and stake your delphiniums then choose from the shorter varieties!

Growing Delphiniums from seed produce amazing blue flowersHere are some of my favorite and reliable delphinium seed vendors:

  • Katrina and Jason Hindmarsh of New Zealand Delphiniums are amazing growers and breeders of Delphiniums. Their New Millennium Delphiniums are known for being reliable performers, strong stemmed, vibrant colors and heat tolerant.
  • Burpee is renowned for their high quality seed and I’ve always gotten terrific germination from their seed. They don’t offer a lot of delphinium varieties but do have some unique offerings that include a red delphinium!
  • Geoseed is a small company out of South Carolina. They offer the most variety of Delphinium seed that I have seen and also sell in wholesale quantities. 
  • The seed from True Leaf Market has been exceptionally good for us. They have large selection of colors for both the Pacific Giants and the shorter Magic Fountains. Their prices are excellent and the seeds can be bought in larger quantities.

Once you receive your seeds its important to store them in the freezer for at least 48 hours and keep them there until you are ready to begin. This will help stimulate the natural conditions that these seeds need to germinate.

Essential Tools For Starting Delphiniums

Soil mix

We use a germinating mix that is fine textured and contains natural microbes called Mycorrhizae that help support root growth. We found that once we switched the plant growth had more vitality and strength. When seedlings are healthy, they are less prone to disease. 

Seed Trays

Delphinium seedlings growing in the greenhouse.When we were commercial growers and needing to start 1000’s of seeds we used what is commonly called “288 plug trays”. They have very tiny cells for germinating seeds in a small space. Once the seedling had its true leaves, we would transplant them into 32 cell trays that could be separated into 4-cell packs and grow on until ready for shipping. As a home gardener it would be much easier to start with a 32-cell tray that contains individual pots. I’ve found this sturdy and reusable tray, with inserts and cover is just the ticket to get my plants started. 

Heat mat

A heat mat will accelerate seed germination and encourage root development by maintaining soil temperatures at approximately 70º F. It really is a game changer for germinating any plant you want to grow from seed. You may not have a lot of control over the air temps but these mats will give consistent heat where it counts: at the root system. 


Don’t forget to label your plants! You’ll never figure it out later. Just some 4” wooden markers will do the trick. We always put the name of the plant and the planting date on the tag. 

Watering Tools

When the plants are young or still germinating, I would use a mister to keep the soil mix damp. After the plants have some strength you can use any watering tool that has a soft flow nozzle on it. We use the Dramm 1” diameter nozzle. It can saturate the soil without disturbing the plants and soil.


The soil mix has enough starter nutrients for germination. Once the plants have their first or second leaves it’s time to feed the seedlings for good strong growth. We’ve always added liquid fertilizer to our watering regiment. There are two basic options: the first is using an organic fertilizer like FoxFarm Big Bloom® Liquid Plant Food Concentrate or non-organic but very effective Miracle-Gro® Water Soluble Bloom Booster Flower Food. Both work great but Miracle-Gro is more cost effective if you are on a budget.

Creating the Ideal Growing Environment

Magic Fountain Delphinium Grown from seed.The perfect environment would be to have a greenhouse but I am going to assume you don’t have one. Never the less, you’ll need to consider some factors to incorporate into you indoor growing plan.

Light Requirements

Lighting is essential! Healthy growth is dependent on the delphinium seedlings getting enough light. So if you don’t have a spot where they can get 8 hours of sun a day, you will want to add supplemental light by using LED Grow Lights. These cost-effective light bars offer energy-efficient, full-spectrum lighting ideal for germinating your seeds.

Temperature Considerations

We have always germinated our delphinium seeds using a heat mat to maintain a temperature of 70 degrees until they have their first true leaves. After that initial phase we keep temperatures between 60°F and 70°F to foster healthy seedling development.

When To Sow Delphinium Seeds

New Zealand Delphiniums grown from seed.Sow delphinium seeds at the right time for your climate. Plan your planting to start about 6-8 weeks before you plan on transplanting. Keep in mind you will also need 3-5 days to condition your plants to the harsh realities of outside living by hardening them off.

This is what we do to start our Delphiniums from seed:

  • Fill your seedling packs to the brim with your soil mix. Then water the soil. It may take a few attempts before the soil will start absorbing the water.
  • Once you see the water has moistened the soil through to the bottom, you can make simple impressions on top with your finger in each cell. Just a 1/8” deep. Place one or two seed on each impression.
  • Sprinkle more soil mix on top to just cover each seed. Mist the new soil and cover with a humidity dome or a sheet of plastic.
  • Don’t forget to label your plants and then place the tray on the heating pad in a well-lit area.
  • Seedlings will begin to emerge in 10-21 days, sporadically after that depending on the vigor of the seed.

Caring for Seedlings

After germination and the seedlings have their true leaves, continue to be vigilant.

  • Strike a balance between keeping the soil consistently moist and preventing water-related issues such as damping off. Damping off is a fungal disease that affects young seedlings. It typically manifests as a sudden collapse of the seedling’s stem near the soil level, causing it to wither and die. 
  • Regularly check soil moisture levels to ensure a Goldilocks scenario—not too wet, not too dry. Delphiniums are sensitive to overwatering, which can lead to root rot.
  • Fuel the growth of your delphinium seedlings with proper nutrient management. Choose a balanced fertilizer and apply it judiciously to provide the necessary nutrients without overwhelming the delicate roots.
  • Nurture your seedlings with care and attention. Regular monitoring, proper nutrition, and a vigilant eye for any signs of stress contribute to the overall health and vigor of your delphiniums.
  • At some point you will need to thin your plants down to one plant per pot. Adequate spacing allows each seedling to receive sufficient light, air, and nutrients. 

Addressing Common Challenges

Attentiveness is key in identifying potential threats. Regularly inspect your delphiniums for problems. Recognizing signs of nutrient deficiencies is crucial for maintaining the health of your delphiniums. Adjust nutrient levels as needed, but avoid over-fertilizing, as this can lead to nutrient imbalances and leggy growth.

Transplanting Seedlings

Delphiniums and PoppiesTiming is of the essence when transplanting delphinium seedlings. Wait until they have reached a sufficient size, typically with several sets of true leaves, before considering transplantation.

Accurately gauge seedling maturity by assessing factors like leaf development, root growth, and overall vigor. You should be able to see white roots when removing the seedling from the pot. Well-established seedlings are better equipped to handle the stress of transplantation.

Prepare both your delphiniums and the transplanting site for a seamless transition. Water the seedlings thoroughly before transplanting, and ensure the destination soil is well-prepared. See my post about growing Delphiniums in the garden here.

Proper transplanting techniques minimizes stress on your delphiniums. Handle seedlings carefully, disturb roots as little as possible, and ensure they are planted at the same depth as they were in their previous containers.

Protect the delicate root systems of your delphiniums by exercising caution during the transplantation process. Minimize root disturbance to facilitate a smooth transition and prevent transplant shock. Shield newly transplanted delphiniums from extreme weather conditions and monitor them closely during the initial days to ensure a healthy adjustment.

Hardening Off Process

Gradually expose your delphiniums to outdoor conditions through a hardening off process. This acclimatization period toughens the plants, reducing the risk of shock when permanently planted in the garden. Sudden exposure to harsh outdoor elements can stress your delphiniums, compromising their overall health and resilience.

Post-Planting Care

Provide a thorough watering to settle the soil and encourage root establishment. While consistent moisture is crucial, avoid waterlogged conditions, as these can lead to root rot. Establish a consistent watering routine to sustain your delphiniums throughout the growing season. Water deeply and consistently, especially during dry periods, to promote healthy growth and vibrant blooms.

Keep a keen eye on emerging leaves, stems, and the formation of buds as your plants progress toward maturity. Vibrant green foliage, sturdy stems, and well-formed buds are positive signs of a robust and flourishing plant.

In a Nutshell

Cultivating delphiniums from seed grants you access to a wider array of varieties and proves cost-effective in the long run. By adhering to key steps such as selecting quality seeds, utilizing essential tools like heat mats and proper soil mixes, and creating an ideal growing environment, you can successfully nurture your delphinium seedlings from start to finish.

Throughout the process, from germination to transplantation and beyond, careful attention to detail and proactive care are essential. With patience, diligence, and a touch of green-thumb finesse, you too can grow delphiniums from seed. Happy gardening!


Why should I consider starting delphiniums from seed?

Starting delphiniums from seed grants you access to a wider variety of options compared to purchasing established plants. Additionally, it proves to be more cost-effective in the long run.

How do I choose the right delphinium seeds?

Select high-quality seeds from reputable suppliers to ensure freshness and viability. Consider factors such as flower color, height, and stem strength to tailor your choice to your garden’s needs.

Can you recommend any reliable delphinium seed vendors?

Certainly! Some reliable delphinium seed vendors include New Zealand Delphiniums, Burpee, Geoseed, and Mountain Valley Seed Company. Each offers a diverse selection of quality seeds.

What essential tools and materials do I need for starting delphiniums from seed?

Essential tools include soil mix, seed trays, heat mats, labels, watering tools, and fertilizer. These items create an optimal environment for successful seed germination and seedling growth.

How do I create the ideal growing environment for delphinium seedlings?

Ensure adequate lighting, temperature control, and proper timing for sowing seeds. Supplemental light sources like LED grow lights and maintaining soil temperatures with heat mats are essential for healthy growth.

What are some common challenges I may encounter when growing delphiniums from seed?

Common challenges include maintaining proper soil moisture levels, preventing water-related issues like damping off, and addressing nutrient deficiencies. Regular monitoring and proactive care are key to overcoming these challenges.

How do I transplant delphinium seedlings successfully?

Wait until seedlings have reached a sufficient size with several sets of true leaves before transplanting. Handle seedlings carefully, minimize root disturbance, and provide post-transplant care to ensure a smooth transition and prevent transplant shock.

What is the hardening off process, and why is it important?

The hardening off process involves gradually exposing seedlings to outdoor conditions to toughen them up before permanent planting in the garden. This reduces the risk of shock and ensures healthy adaptation to outdoor elements.

How do I care for delphiniums post-planting?

Provide thorough watering to encourage root establishment and maintain consistent moisture levels. Monitor plant growth, address any issues promptly, and nurture plants with proper nutrition to promote healthy growth and vibrant blooms.

4 Responses

  1. Oh how I miss you and those trays of beautiful, healthy plants!

    Your delphiniums were/ are my favorites!

    Our growing time here in zone 5 is so short, but spring seems early.
    Yesterday I ordered 8 delphinium plants from Burpee.

    Thank you for your wonderfully understandable and encouraging instructions for growing delphiniums from seed. I may dare to try!

    Thank you so much!

    1. Thanks so much Angela! I hope your garden flourishes and I really think you’ll find starting delphiniums from seed more of a fun challenge. You can do it!

  2. I’m so glad you’re enjoying retirement, and just as glad you’re sharing your expertise with your old customers. Your gorgeous delphiniums were always the highlight of my garden. This is my first year trying to grow my own from seed and the seedlings are just starting to emerge, so I’ve ordered grow lights and will follow your feeding and transplanting advice. Fingers crossed I get at least a few healthy plants this year. Thanks so much!

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Welcome Gardening Friends!
Amanda in Greenhouse with blooming Delphiniums. She loves growing flowers!

Amanda Shenstone

Flower Lover, Grower, Gardener

As part of Graceful Gardens for decades, I’ve garnered a wealth of knowledge about growing Delphiniums, perennials and annual flowers, and I am eager to share these insights with all of you.

Amanda Shenstone


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