Sweet Pea Gardening Guide: How to Grow Sweet Peas

Sweet peas are fragrant flowering plants known for their beautiful pastel and bicolor petals. Historians credit Francis Cupani, a monk from Sicily, as the originator of sweet peas in 1699, but famed horticulturist, Henry Eckford, popularized the plants in the late 1800s. Selecting for only the most pleasing cultivars, Eckford created a breed of plant that is now known the world over for its impressive display of color and sweet aroma.

While the most common variety of sweet pea is an annual (Lathyrus odoratus), they also come in perennial varieties (Lathyrus latifolius).

1. 1. Annual sweet peas: Annual sweet peas complete their entire life cycle in one growing season. Like other annual crops, they germinate, grow, produce seeds, and die within the course of a year. If you want to grow them again, you’ll need to replant new plants in your garden the following year. Most sweet pea varieties are annuals.
2. 2. Perennial sweet peas: Perennial sweet peas come back year after year. You do not need to replant them after the growing season ends, and they will continue to grow for a longer period of time. Perennial sweet pea varieties may be easier to grow, but there are fewer to choose from and they tend to lack that classic sweet pea fragrance.

When you choose to grow sweet peas, your options abound. Start by familiarizing yourself with these popular cultivars.

1. 1. ‘American’: The ‘American’ sweet pea is an annual heirloom cultivar that blooms to reveal wavy stripes of red and white.
2. 2. ‘Old Spice’: ‘Old Spice’ comes in shades of pink, lavender, cream, and white. This annual sweet pea cultivar has especially delicate stems and leaves.
3. 3. 'Erewhon': This annual sweet pea cultivar features a mix of light purple-pink and deep violet flowers. It is known for being particularly fragrant.
4. 4. ‘Everlasting Pea’: As the name suggests, ‘Everlasting Pea’ is a perennial sweet pea. It grows quickly and can rapidly cover a trellis.

Sweet peas are fairly hardy plants that grow abundantly—so long as you set them up for success.

• Determine your hardiness zone. Despite their delicate appearance, sweet peas are surprisingly hardy. They prefer cooler conditions and thrive when planted in soil temperatures between 55 to 65 degrees Fahrenheit. When planted in hardiness zones 7 to 10, sweet pea seeds can be sown in the fall. In zones 6 and below, it's best to sow your seeds in late winter or early spring for an early-summer harvest.
• Choose the site. Sweet peas prefer areas that get full sun in the morning and shade in the afternoon. Their leaves love the light, but afternoon shade helps keep their roots cool and moist.
• Prepare the soil. Plant your sweet peas in well-draining, alkaline soil that is rich in organic matter. If your soil tends to be on the acidic side, sprinkle lime on the soil's surface. Sweet peas require a soil rich in nutrients and thrive in soil with a mixture of compost and manure.
• Construct a trellis. Sweet peas are climbers and require a sturdy structure on which to grow. If you have the space to plant your sweet peas in rows, place tall posts about eight feet apart along the rows. Attach netting or metal fencing to the posts for the sweet peas to cling to.
• Plant your seeds. Plant your seeds in two rows, one on each side of the trellis. Make a four-inch trench in your compost, poke holes in the soil with a pencil, and drop in your seeds about six inches apart. Press down firmly to close the soil over the seeds, blocking out any light.
• Water sweet pea seeds lightly at first. Give your seeds a light watering immediately after planting to keep them hydrated and settle the soil. It’s important to keep the soil moist but not soaking wet.

Sweet peas need regular maintenance, but with a few growing tips, they can be rewarding plants to care for.

• Water sweet peas daily. Sweet peas need lots of water, especially during hot summer months, so make sure to water them daily. Set up a soaker hose to make watering more efficient.
• Support the fast-growing vines. Sweet pea vines grow rapidly, and it's crucial that they remain tied to their trellises. Use an organic material, like twine, to keep your vines connected to their trellises.
• Add mulch. Once your plants are established, laying down a layer of mulch will help the soil retain water and keep the roots cool.
• Deadhead sweet peas. Regularly deadheading your flowers, or removing spent blooms, will promote healthy vine growth.
• Cut flowers early in the day. To show off your sweet peas in a vase or bouquet, make sure to cut your stems early in the day before the sun has dehydrated the blossoms. Only cut side growth, not the main stems. For the longest vase life, choose stems that have at least two unopened buds on them, and add plant food to the vase water.

Grow your own garden with Ron Finley, the self-described "Gangster Gardener." Get the MasterClass Annual Membership and learn how to cultivate fresh herbs and vegetables, keep your house plants alive, and use compost to make your community—and the world—a better place.