The first flowers that I successfully sowed from seeds were Sweet Peas. They were part of my first cut flower garden, where I predominantly grew Sweet Peas and Dahlias. That season, my tulips didn't come up (I’m blaming the squirrels), and many other seeds only produced a few flowers, but the sweet peas persevered. This small triumph in seed starting gave me the confidence to try it again!
I've delved deep into the last couple of seasons, studying what makes these fragrant flowers flourish, and I want to share a few crucial tips with you below.
**When to Sow:**
Timing is probably the most important aspect of growing sweet peas. They thrive in cool temperatures. There are different options for when to sow them, depending on your growing zone and your garden's microclimate.
**Fall Sowing (Zone 7 and up):**
If you are in a mild climate or an area with hot spring temperatures, experiment by sowing sweet peas in the fall and overwintering them. Sweet peas are very cold-hardy and can survive frosty days and even snow.
My first year growing sweet peas on a large scale, I pre-soaked the seeds indoors, then planted them in garden beds in September/October. We experienced quite a bit of snow and cold temperatures that year, so I covered them with frost cloth, although now I think it wasn't totally necessary. Sweet peas can handle cold snaps as low as the 20s, and snow provides a layer of insulation.
(Sweet peas are in the middle row (with t-posts) under the low tunnel right before a heavy snow fall)
They grew into a beautiful wall loved by birds, bees, butterflies, and my kids, offering a delightful shade from the hot summer sun.
**Winter Sowing Indoors (Zone 7-5):**
Many gardeners prefer to directly sow their seeds in the ground to save space and materials for an indoor setup. If you fall into this category, that's okay. Sweet peas can be started either way – directly in the ground (read below) or indoors. I prefer starting sweet pea seeds in seed trays to have better control over germination and to know exactly how many plants are going into the field.
You can start your sweet peas as early as January/February indoors! I got started last week (01/29) and will be sowing more this week.
**Early Spring Sowing (Zone 5 and lower):**
If you are in a colder zone, you can start with sweet peas in the early spring months, around the end of February/March. Start indoors to get a jump start on germinating the seeds and growing little plants that you can transplant as soon as the ground is workable. Hint: you don't have to wait until your last frost date; plant them outside as soon as your ground isn't frozen anymore.
What I love about sweet pea seeds is how versatile and easy to handle they are due to their relatively large size compared to other flower seeds. There are a few ways to kick off the germination/sprouting process:
- Soak the seeds overnight
- Plant without soaking
Both of these methods work for direct seeding outside or starting in pots/seed trays.
Soak for 1-3 days wrapped in a wet paper towel inside a ziplock bag. I simply leave the ziplock bag on the kitchen counter. Check daily to ensure the seeds aren't drying out or rotting.
(Sweet peas starting to sprout after being soaked for 3 days in a wet paper towel)
After soaking (or not), plant the seeds ¼” deep into a pre-moistened seed-starting mix and cover up the seeds.
Use deep pots, as sweet peas need lots of room for their long roots. You can place multiple seeds per pot and space them out. Gently pull them apart when transplanting.
(30 hole tray with 3 seeds in each pot)
(Pre-soaked sweet pea seeds going into pots)
Keep at 50-55 degrees for germination. Use your garage, basement, sunroom, or a cool greenhouse.
Once your seeds have germinated and have some green shoots, move them to 35-50 degrees in full sun/under lights.
If you live in a place with mild temperatures in the winter, you can set your pots outside (occasional cold snaps down to 20 are fine!). Just make sure to protect the little plants from mice and birds. If temperatures drop significantly for a prolonged period, you can move the pots somewhere more sheltered.
Transplant when the plants are a few inches tall and/or your ground is workable. Plant them in compost-rich soil in a sunny spot. Sweet peas are heavy feeders. Make sure to add some compost or manure to your planting area.
(Sweet Peas growing up a cattle panel arch)
Provide a trellis or some kind of support right away. Sweet peas use their tendrils to climb up. The support should be no thicker than a pencil for them to wrap around. You can build a cattle wire arch, use flower netting attached to a T-post, or whatever you can find googling.
Tie your sweet peas weekly to help them climb up and stay there.
The plants can grow as tall as 6ft.
To keep sweet peas blooming throughout the season, make sure to cut regularly and remove spent blooms. Harvest when half of the flowers on a stem are open. You can cut just the stem or the vine for longer bunches.
The flowers will shut down when temperatures reach 80F.
Sweet peas last about 3 days in the vase. The flowers are ethylene-sensitive, so keep them away from ripening apples. :)
My favorite varieties last year were Castle Wellan and Noel Sutton. Both had the healthiest plants with strong stems and LARGE flowers.
The subtle pink edge of Castle Wellan had a very romantic look, and the vines reached far up our cattle panel arch. Whereas I loved the deep blue coloring and abundance of flowers of Noel Sutton.