Photo: Katya iz Kieva.
Starting Verbena Bonariensis: Sowing Dates, Seed Saving, and Winter Hardiness
Nadezhda 69 wrote:
When do you normally start it indoors?
Nadya, I sow Verbena bonariensis every single year. Always surface-sow, do not cover the seeds with dirt at all. I usually start mine in early March. Once up, they develop at an average pace just like standard annual flower starts.
Growth is definitely on the slower side, and it blooms late, roughly mid-July all the way into October. Pro tip: always plant several stems close together in a clump. A lone single plant looks pretty sparse and spindly on its own.
Georginka wrote:
develops at an average pace just like standard annual flower starts…
Funny, in my trays last spring verbena took its sweet time. My petunias were already growing like absolute beasts, while the verbena was still tiny little things. They were pretty small when I finally transplanted them into garden beds too.
Can you collect viable seeds from it at the end of the season, or does our short summer cut it too close? As I understand it, it won’t survive our winters and is grown strictly as an annual here, right? Read somewhere online that folks dig up the root crowns in late fall, pot them up, and stash them in a cold cellar over the winter. Anyone ever tried that?
Nadezhda 69 wrote:
Can you collect viable seeds from it…
I cut flower heads back in late September and dried them out indoors, but barely found any actual seeds inside, mostly just dry chaff. Honestly don’t even know if anything will sprout from that batch.
That said, a grower friend over in Novosibirsk swears her seeds fully mature and she saves her own every year. Maybe my season was just off, or maybe the specific cultivar I grew (Vanity) is sterile or needs more heat.
Nadezhda 69 wrote:
shelf space under grow lights is limited…
Mine stay directly under good LED grow lights, so they make steady progress. They pause for a brief moment after pricking out, but catch up quickly. By planting-out time, they are respectable, bushy little plants.
lusi wrote:
mostly just dry chaff…
I crushed seedheads straight over garden soil one fall hoping for self-sown volunteers the following spring. Not a single green sprout ever came up! That’s why I just bite the bullet and order fresh seed every year.
It is such a delicate, airy flower. I tuck it right in between my shrub roses and bundle it under the winter rose insulation covers in late fall. Believe it or not, it survived our Zone 4 winter completely intact last year! Totally caught me by surprise. We will see if it pulls off the same trick this spring.
Full Summary: Growing Verbena Bonariensis in Cold Climates
- 🌱 Sowing Method: Surface-sow only. Verbena bonariensis requires light to germinate. Do not cover with potting mix; mist lightly with water to seat the seed.
- ⏱️ Sowing Timelines: Early February sowing produces blooms by mid-July. Sowing in early March works well if provided with continuous high-intensity LED grow lights.
- 🌿 Growth Habit: Seedlings develop slower than petunias and look delicate. For the best garden display, transplant in clusters of 3 to 5 plants so stems support each other and create a full purple haze.
- ❄️ Winter Hardiness & Overwintering: Rated hardy only to USDA Zone 7. In Zones 4-5, it is treated as an annual. Self-seeding is unreliable in cold wet soils, but plants tucked into protected microclimates (such as insulated winter rose shelters) can successfully overwinter as perennials.
- 📦 Seed Saving: Short northern summers often fail to produce plump, viable seeds before frost, leaving seedheads full of empty chaff. Fresh commercial seed delivers vastly superior germination.
