Hmmmm.....I have always found sweet peas work best when direct sowed in place outside. And they can be planted in the ground as soon as the soil can be worked (no longer frozen or water-logged) - no reason or need to wait for last frost :-) You can do the same with garden peas.

You can get a slight jump on the season if you start seeds indoors but they develop a long tap root and can be difficult to transplant for that reason. Again, no need to wait for last frost date but harden the starts off for at least a week before planting out.

These are cool season annuals that need to get established and growing well before warm weather hits, hence the early planting date. And they can take a good amount of cold, as well....even light frosts. President's Day weekend is the trigger date for sweet peas in the PNW and I am getting ready to plant mine now (last frost date here is end of March- early April).

Yup, that was my thought last year, and I planted dozens of fresh seeds last year outside in various beds around my yard. Did I not water enough? Or too much rain? Don't know what happened but I got very little germination. So I bought two Rootrainers which are just for this purpose and want to try to start the seeds inside this year.

It is important to soak the seeds overnight or for at least 8 hours before planting. This softens the seed coat and makes germination faster and easier.

Sweet peas like a deep and very fertile soil wth good drainage. They need regular fertilization and watering during the growing season and it helps to shelter/shade the root zone with some other low growing annual if possible.

I had a bumper crop going last spring........until the deer found them and munched all the buds and vines back to about 6 inches :-(

Thanks. Whatever it was last year, there was something I didn't do right. I think sometime around June (three months after sowing!), I got a measly little seedling showing up in one flower bed.

Ouch about the deer.

Anyway, what are your thoughts about how many weeks before average last frost I should start the seeds indoors? I'll probably shoot for 6.

I started mine indoors four weeks ago. It depends on your climate but in mine if you wait for the soil to be warm enough for the seeds to germinate outdoors it will be well into the season before they flower. I germinate them in the kitchen and then move to my unheated greenhouse. I don't soak the seed. Start them in long pots or toilet roll cores to get around the taproot issue.

Floral, they will germinate in very low soil temps......even as low as 40F. If I waited for the soil to warm up adequately here before planting, it would be June before anything happened!! But germination IS much slower in colder soils. That's what the soaking will pre-empt.

FWIW, in my climate it is even suggested that the seeds be planted in late fall. They should be up and growing by early to mid March if you follow that practice. My garden is just too vulnerable in winter....the deer were checking out that bed yesterday.......and my pea area too shady until well into spring for me to have good success with that practice.

They germinate quicker in warmer soil. The RHS recommends 59f. I never soak seed because I cannot guarantee that I will have the time or theweather to be able to sow once they're soaked. Autumn sowing is also used here but in containers which are then overwintered in a cold frame.

Link for Rick: https://www.rhs.org.uk/advice/profile?PID=464