Germination Trick for Delphinium Seeds (Cold Stratification in Fridge)

Delphinium seeds are difficult to germinate without extra help. This method shows how to use your fridge to cold stratify delphinium seeds prior to sowing to ensure better germination rates.

If you are new to growing delphiniums, also see the guide, How to Grow Delphiniums.

How to Germinate Difficult Seeds

Delphinium | Genus: Delphinium

Delphinium Growing Guide
Herbaceous perennial
• Hardiness zones 3a to 8b
• Full or part sun
• Well-draining loam is best
• Native to North America and African mountains and considered non-invasive
• Chill dampened seeds for better germination

Shop Online: Buy delphinium seeds at Botanical Interests (US shipping)

Over the years I have grown a lot of delphinium plants from seed but it has not always been easy.

There are lots of varieties with different characteristics and temperaments. You’ve probably noticed that the instructions on seed packets can vary quite a bit as well.

But, if you think about it, delphiniums all have a common ancestry as a mountain plant that needs a cool winter to precede germination to later produce those gorgeous summer blooms.

And that’s a big hint about how their germination works too as you’ll see.

Each year I start a bunch of delphinium plants indoors from seed and transplant them outdoors when the risk of frost has passed.

Some seed packets mention the seeds need cold stratification prior to sowing, but usually do not provide any helpful tips on how to do this.

After wasting a few packets of seeds on failed attempts in my early years, I stumbled upon a fridge method that both improves germination rates and as well as improving the time it takes for the seeds to sprout.

This is by no means a scientific study—just my own anecdotal evidence—but it has proven consistently reliable and is now part of my routine.

The trick is a combination of moisture and cooling using either of the methods below.

Contents

How to Improve Delphinium Germination

Fridge Method

I have experimented with various methods to encourage delphinium seed germination for years.

This next part describes some of the things I have tried (with varying success).

I always use seeds from the same pack for all 3 options so I’m fairly confident it’s not an issue with the actual seeds.

1. Sow straight out of packet | 20% germination rate after 16 days. Did not improve after that time period.
2. Chill seeds in their packet in fridge for 1 week | 50% germination rate after 16 days (no change after that).
3. Place seeds sandwiched between sheets of moist paper towel in a bag or food container in fridge for 36 hours | 90% germination rate after 11 days (no change after that).

After trying this with numerous varieties, it seems the combination of exposing the seeds to moisture along with the chill is the winner. Most seed packets just advice a dry chill, which is not as effective as a wet chill.

Why 36 hours?

It works. I realize some seed packets advise a much longer chill period (up to several weeks) but I’ve found that after just 24-36 hours—if moisture is present—the seeds are ready to sprout. I do this with a standard fridge temperature is between 34 to 39°F (1 to 4°C). Again, it’s just my experience so try it yourself to find out. Your conditions may be different and give different results. But faster is fine with me!

Alternate Method

This method shown by Miriam Goldberger of Wildflower Farm has a similar process perfect for tough-to-germinate seeds. It’s a good one to try for various native plants.

Miriam’s Fast Cold Moist Stratification Method

1. Moisten loose growing medium (or a small flower pot filled with moist growing medium) in labelled ziplock freezer bag.
2. Add wildflower seeds.
3. Place in fridge for 24 hours.
4. Next, place in freezer for 24 hours.
5. Next, place back in fridge for 24 hours.
6. Continue for 3 to 4 cycles (4x each in fridge and freezer).

As you can see, we’re not scientists but just gardeners who like to experiment. And, when we get good results over and over again, we repeat what works.

Seed Germination Test

After cold stratification, you can check your delphinium seeds for viability prior to sowing in soil. This is particularly helpful for older seeds you are unsure about since viability diminishes as time marches on.

See How To Check If Seed Are Viable for step-by-step instructions.

Sowing Seeds After Moist Chilling

The optimum soil temperature range for germinating delphinium seeds is 60-68° F (15-20°C).
Also, be sure to keep the potting mix or soil moist.

Once you’ve given the seeds a jump start with the cool/moist fridge method, be sure the rest of your seed starting process is sound. You will get the fastest seed germination if you can start the (already chilled) seeds in the optimum soil temperature range: 60-68° F (15-20°C).

Depending on the time of year, you may be sowing the seeds directly outdoors, if there are at least 6-8 weeks before first frost, or indoors.

Sowing indoors means using a proper seed starting mix, and providing light, moisture, air, and warmth just how they like it.

I have a complete guide to indoor seed sowing here with lots of detail.

Read your seed packet for specific instructions and be a good plant caregiver.

Winter Sowing

Winter sowing delphinium seeds is another option. While you can direct sow the seeds outdoors in fall—and hope nature provides what’s needed—you can also use the “milk jug” method.

This explains winter sowing in detail. Basically, you sow seeds in reused plastic containers like milk jugs, food clamshells, and plastic bins—anything clear or translucent that lets light in. Placed out in the garden in the snow, the seeds are first chilled and then begin to act like mini greenhouses as the light and warmth increases in spring.

You do have to monitor your seeds with this method, watering as needed and venting the containers if they get too warm inside. It’s fun to try and a great way to keep the garden endorphins going year-round.

Resources

Ebook

Seed Starting for Beginners
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by Melissa J. Will

Everything you need to get started with indoor seed starting for indoor and outdoor plants. Grow what you want—any time of year!

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Do Your Own Experiments

Experimenting—along with reading trusted sources (not folklore)—is a big part of becoming a great gardener.

For seeds like this, I encourage you to set up your own experiment.

With different seeds and conditions (fridge or fridge and freezer and exposure to moisture), do some tests.

Divide your seeds into several groups and compare ultimate germination rates over various time periods (3 days, 1 week, 2 weeks, 3 weeks).

See if you too find cold + moisture is the key to success.

This has more tips on various cold-moist stratification methods.

More Propagation Tips

Basal Root Cuttings

Another little-known method for propagating delphiniums is to take basal root cuttings in spring.

This is done in spring outdoors when the new shoots are just a few inches tall before the stalks get hollow.

I don’t have a tutorial here but do google it or get a good resource guide on plant propagation methods (see below). It’s a faster way to multiply your plants but the window of opportunity is brief.

Spring Sowing Tips

Spring gardening in general can befuddle us—what can we plant or sow before the last frost of the season?

This is a helpful guide:

~Melissa the Empress of Dirt ♛

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