When I first heard the term cool hardy flowers, I was intrigued. Even though I have been gardening for many years, I had never heard of them until recently. I often find that when the spring bulbs are done blooming, there’s a lull in the garden before the summer flowers begin blooming.
If there were flowers that could handle cooler temperatures and would allow me to get in the dirt earlier then I was willing to give them a try. I quickly learned early on that there is not a lot of information out there on this topic with the exception of the book: Cool Flowers by Lisa Mason Ziegler.
My goal today is to make your journey to planning, planting and growing easy; this is the quick how-to guide on cool hardy flowers that I wish I had.
One of the joys of gardening is learning by experience. It’s not a large investment to put a few seeds in some soil and the pay back will be sure to be rewarding.
The information here may depend on what hardiness zone you are in. You can easily look that up here:
I live in the northern hemisphere in zone 6a with my average last frost date around May 20. I begin hardening off my cold hardy flowers around March 20 to plant outside in the garden by the first week of April.
No matter what zone you’re in; you’ll want to start hardening off your cool hardy flowers 2 months before your last frost date to be able to plant them out 6 weeks before your last frost date.
The information below is based on Zone 6a with a last frost date of May 20:
A List of 5 Cool Hardy Flowers to Plant for a Spring Garden
and when to plant them outdoors
- Bells of Ireland Store seeds in refrigerator | Sow in the beginning of March | Harden off around March 20 to plant out the first week of April
- Bachelor Buttons Store seeds in refrigerator for cold stratification | Sow in March Harden off around March 20 to plant out the first week of April
- Orlaya sow in February Harden off around March 20 to plant out the first week of April
- Feverfew direct seed 4 to 6 weeks before the last frost
- Sweet Peas sow the beginning of March. Can tolerate temperatures as low as -4 Celsius (24 Fahrenheit)
More Cool Hardy Annuals To Try!
This list is not exhaustive but these are some more flowers I have successfully grown in my spring garden. I would love to hear what flowers you have tried.
- Nigella “Love in a Mist” sow in February
- Snapdragons sow the end of February
- Bupleurum sow in March
- Dara sow in February
- Ammi sow in February
- Yarrow sow in February * not an annual but likes a cold start
- Chinese Forget me Not
It’s still important to harden off your Cool Hardy Annuals even though they can handle cooler temperatures. Here’s the easy day by day method for hardening off that I use:
How To Harden Off Spring Cut Flowers Seedlings
- Day 1: place the plants outdoors in the shade for 2 hours
- Day 2: place the plants outdoors in the shade for 4 hours
- Day 3: place the plants in dappled shade for 6 hours
- Day 4: Place the plants in dappled sun/shade for 8 hours
- Day 5: Place the plants in dappled sun/shade for 10 hours
- Day 6: Place the plants in sun for 12 hours
- Days 7-14: Keep the plants outside unless the temperatures go below freezing 0 C or 32 F