I'm having the worst time with this. They come up in the garden every year eventually, but I want them earlier and where I want them.
I cluster sow in a 2" pot on the surface of seed starting mix, water with 9:1 peroxide mix and a drop of Superthrive (first time using this year, it's been fab!), and put the pot inthe Biodome over a heat mat. Soil temps hover between 70-80 degrees. Nearly everything else loves it, germinates early. I know Verbena Bonariensis is a slow starter, but it's been nearly 3 weeks. Does it need darkness? Cold? Is Deno better? The seeds seem too small to soak, but should I? Any help greatly appreciated!
Pam, I'd also watch your temperatures closely. Some species really like the warm, but for many getting towards 80 degrees is too hot. If it is really cool in your house where you are germinating, I'd put pots of cool germinators next to flats that are on a heat mat to give them a little warmth without getting them too hot.
Also if you don't have one, I'd recommend you look into getting a thermostat for your heat mat to prevent them from overheating. I just bought a digital one from Amazon for under $30. (Hydro Farm brand)