Figuring Out So Cal Flowers

What’s “Early Spring”?

I’ve been reading a book called Cool Flowers by Lisa Mason Ziegler. It’s a wonderful introduction to the practice of overwintering flowers (those that will tolerate it) so the plants can develop strong roots and stems over the winter and bloom earlier and more profusely than their siblings planted in spring.

One example of this, which I’ve been practicing for a few years now, is sweet peas. I plant them in October and over the winter they develop strong, deep roots that support thick stems. Come spring I get a February/March bloom, with healthy, vigorous plants producing through April and early May.

Why, then, was I so frustrated the other night when I tried to apply the Cool Flowers calendar to other flowers in my garden? (By the way, “overwintering” is for “hardy annuals”–those annual plants that can withstand cold winter temps. There are plenty of them here in Zone 10a because our winters are so mild.)

Here’s what it looked like:

Me: Okay! Let’s do this.

Book: Find your first and last frost date.

Me: I have no frost date. It’s San Diego. Rarely do we see frost near the coast.

Book: Now, subtract six to eight weeks from your last frost date to find your “early spring.” Early spring is a great time to plant flowers for strong and early blooms!

Me: Like I said, I have no frost date.


Me, frustrated, checking my math: Let’s see here, my last frost date is never. “Never” minus eight weeks is…”never.”


Me, researching on my computer: Okay, I see that there’s a 50% chance of frost in the month of January and that’s about it, so let’s pretend my last frost date is January 31, because that’s the closest thing I have to a frost date.

Me, calculating: January 31 minus eight weeks is…December 6. Cool! I have a date. Except, well, wait.

December 6 is “early spring”? I think San Diego temps in December are probably similar to zones 6 through 8 in February and March. However, if any of these plants care about daylight hours, December is when our daylight hours dip below 10 hours/day, which is the minimum for most flowers.

So, while a lot of books or instructions might say they’re good for zones six and up, they’re kind of lying. It’s different here in San Diego and I’ve set out on a quest to create a calendar for flowers year-round in Southern California. Especially zone 10a like me.

A Cool Key to Snapdragons

Once I narrowed my problem, I began to get answers. Let’s start with an email I sent to Johnny’s Selected Seeds and their reply. By the way, Johnny’s has a wonderful feature called “Ask a Grower,” and so that’s what I did. I told them about my “never frost date” predicament and begged for help on figuring out when to start snapdragons. Johnny’s sells snapdragon seeds across these groups:

  • Group 1: Winter and early Spring harvest seasons. These consist of the Legend varieties.
  • Group 1-2: Winter and early Spring harvest seasons. Chantilly varieties.
  • Group 2: Spring and Fall harvest seasons. Bridal and Costa varieties.
  • Group 3: Spring, early Summer and Fall. Costa Summer, Early Opus, Early Potomac varieties.
  • Group 3-4: Late Spring, Summer, early Fall. Orleans, Potomac, Rocket Mix (Summer only).

The dates can overlap a bit, so the grower gave me my very own calendar for Zone 10a. Here it is, below, after I prettied it up a bit.

Amazingly, I already have Chantilly, Costa and Early Opus seedlings planted out in the garden. So this makes me feel better about my decision to do so. I was planning to seed my Early Potomac Sunrise seeds sometime in March or April, but clearly I need to do that earlier, so I’ll start seeds in early February. The Johnny’s grower advises against growing snapdragons here in summer, even though they have heat-tolerant varieties like the Potomac Series. She notes that the plants will grow but their stems will be weak and thin. I’ve actually grown Potomac Lavender here in summer, not knowing what I was doing, and they did quite well (they’re pictured at the top of this post). But I’ll chalk that up to some beginner’s luck and will stick with the chart moving forward. After all, I can live with eight months of snapdragons!

Chantilly Light Salmon Snapdragon
Opus Early Bronze Snapdragon
Costa Velvet Snapdragon

I’m planning to do this type of research on every cut flower I grow. Because I want to know exactly the best time to grow each variety and why. Next on my list will likely be zinnias. I know they’re an easy warm-season flower to grow, but I’ve seen some varying guidance on exactly when they should first go into the ground, either direct seeded or transplanted. So stay tuned!