Some plant seeds are difficult to germinate even though they are fresh and viable. This trick works particularly well for delphiniums to get better germination rates—and faster.
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
• 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
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 they do all have a common ancestry as a mountain plant that needs a cool winter 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.
After wasting a few packets of seeds on failed attempts in my early years, I stumbled upon a trick that both improves germination rates and timing.
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, also known as stratification, before you sow the seeds.
How to Improve Delphinium Germination
I have done all sorts of tests to figure out what works best. This article has been updated over the years to show the most informative results.
This next part shows how I compared different methods.
I always use seeds from the same pack for all 3 options so I know it’s not an issue with the actual seeds.
- Sow straight out of packet | 20% germination rate after 16 days. Did not improve after that time period.
- Chill seeds in fridge for 1 week | 50% germination rate after 16 days (no change after that).
- Place seeds on moist towel in bag 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. 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!
Cold Stratification Trick for Wildflower Seeds
This method shown by Miriam Goldberger of Wildflower Farm has a similar process perfect for tough-to-germinate seeds.
Are These Seeds Still Good?
Seed Viability and Germination Test
- First, follow any recommend preparations for sowing such as scarification (roughing up seed coat) or stratification (e.g. pre-chilling).
- Place 10 seeds at least an inch apart on moist paper towel, coffee filter, or cloth. Fold over and insert in labelled plastic bag.
- Keep in warm, dark place. Most need a 65-75°F | 18-25°C temperature range. Do not allow paper towel to dry out.
- After expected germination period (number of days), check how many seeds sprouted (e.g. 8 out of 10 = 80% germination rate). You can sow any seeds that have germinated. If nothing sprouted after an extra week, the seeds are probably toast.
Keep reading for seed sowing tips.
Sowing Seeds After Moist Chilling
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.
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.
The optimum temperature range for germinating delphinium seeds is 60-68° F (15-20°C) . Also, be sure to keep the potting mix or soil moist.
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.
- How to Read Seed Packets
- How to Troubleshoot Seed Sowing Problems
- How to Give Your Seeds The Best Start
Seed Starting for Beginners
Everything you need to get started with indoor seed starting for indoor and outdoor plants.
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Do Your Own Experiments
Experimenting 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 temperature and humidity levels), your circumstances are not going to be exactly like mine.
Divide your seeds into several groups and compare dry chilling versus chilling while exposed to moisture over various time periods (3 days, 1 week, 2 weeks, 3 weeks).
Whatever you do, start by photographing the seeds and check on them daily for any visible changes.
Take notes and tag everything so you know what’s what.
Find what works best and run with it.
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. It’s a faster way to multiply your plants but the window of opportunity is brief.
These are some of my favorite books on plant propagation. They have photo tutorials for growing plants from a variety of methods. Once you know the basics, it’s super fun and addictive.
Grow Your Own Garden by Carol Klein was the first one I bought and still the one I refer to most.
~Melissa the Empress of Dirt ♛