The colorful and fragrant ornamental sweet pea (Lathyrus odoratus) is a favorite plant for informal cottage gardens and is easy to grow. These Mediterranean natives are full-sun plants that thrive best in moist, rich, slightly alkaline soil during the growing season, often benefitting from bone or blood meal amendments for flowering. These climbing plants are most often seen trained up trellises or fences or spilling over the sides of pots. Despite having "pea" in their name, they are not edible and are toxic to humans and pets.
Learn How to Grow Fragrant Sweet Pea Flowers
|Common Name||Sweet pea, perennial pea, everlasting pea|
|Botanical Name||Lathyrus odoratus|
|Plant Type||Annual, vine|
|Mature Size||6-8 ft. tall|
|Sun Exposure||Full, partial|
|Bloom Time||Summer, Fall|
|Flower Color||Red, pink, blue, white, lavender|
|Hardiness Zones||3-8 (USDA)|
|Native Area||Europe, Mediterranean|
|Toxicity||Toxic to humans and pets|
About Sweet Pea Flowers
Sweet pea (Lathyrus odoratus) is a climbing, flowering, sweet-smelling annual in the legume genus. Originating in the southwest of Italy and the islands of the Mediterranean, sweet pea has been used in gardens since the 17th century.
Sweet peas lend a cottage feel to gardens. Fast-growing sweet peas are an instant nostalgic reminder of the beautiful, rambunctious old-fashioned gardens. These vintage varieties were selected for their vibrant colors and intense fragrance. It reached its modern form under the work of Scottish nurseryman Henry Eckford, who developed dozens of cultivars during the late 1800s.
Modern sweet pea cultivars come in almost every color except yellow, but not all newer sweet pea varieties are fragrant. The mature size will depend on the type you choose to grow but expect the vines to reach 6 to 8 feet tall. They are often grown on bamboo tripods but typically along a trellis or fence for support.
Sweet Pea Care
Here are the main care requirements for growing sweet pea plants:
- Plant your sweet peas in late winter or early spring in a spot that receives full sun.
- Sow two to three seeds together, about 1 inch deep in compost-enriched, well-draining, moist, slightly alkaline soil.
- Keep the soil moist (not soggy); water if the soil feels dry.
- Give more phosphorus- or potassium-heavy fertilizer instead of nitrogen to encourage more blooms.
How to Plant and Soil
Plant sweet peas in the late winter and early spring. Sow three seeds together about a foot between groups of seeds. Plant sweet pea seeds about 1 inch down in the soil. Work compost into the soil about six weeks before planting the seeds for better blooms. Compost will also improve poor soil.
Sweet peas prefer rich but well-drained soil. A slightly alkaline soil pH (about 7.5) is ideal.
Sweet peas thrive in full sun, although in warmer climates, they do well in a location that receives a bit of shade in the afternoon's heat.
Sweet peas need weekly watering to moisten the soil during the growing season. Check the soil by placing your finger an inch into the soil. If it's moist, there's no need to water the plant, but if it's dry, it's time to give the plant a drink.
Temperature and Humidity
Because sweet peas originated in the Mediterranean, they can handle an occasional chill but do best if planted after the last frost and in warmer temperatures in USDA zones 3-8. Sweet pea seedlings can tolerate a light frost, but the plants dislike sweltering temperatures. Plant early to enjoy the blooms before they wither in the heat.
During the growing season, apply fertilizer for sweet peas monthly. Adding a bit of bone or blood meal to the soil can help keep the stems long and suitable for cutting. Choose a fertilizer higher in potassium or phosphorus, or consider a tomato fertilizer.
Types of Sweet Peas
Another plant sweet pea shrub (Polygala spp.) is unrelated to the sweet pea plant (Lathyrus odoratus) but gets its name from its similar-looking flowers.
Cultivars of sweet pea plants (Lathyrus odoratus) include:
- 'Old fashioned': Sweet peas labeled old fashioned should be fragrant.
- Spencer cultivars: These are exceptionally hardy vines with striking coloring, but not all of them are particularly fragrant.
- 'Bijou Group': This is a sweetly scented dwarf variety for containers.
To increase branching, which produces more flowering stems, pinch the growing tips back 1 inch when the plant reaches 4 inches tall. The more you cut the flowers, the more blooms you should get, so don't hesitate to bring some bouquets indoors. Deadhead the spent flowers to encourage continued blooming.
Propagating Sweet Pea
Sweet peas are best grown from seeds; however, you can use seedling cuttings if you do not have seeds yet and want to produce more plants. The cuttings will catch up to soil-grown plants if taken in the early spring.
- What You'll Need: Jar of water, scissors, healthy seedling segment, root hormone (optional)
- Cut a 5 or 6-inch stem segment from a healthy seedling; cut just above a pair of leaves, leaving at least a few nodes to allow for new growth.
- Optionally give rooting hormone to promote healthier, more robust rooting success. If using it, dip the cut end of the stem into the hormone for five seconds, then put the cut end in the jar of water and place it in a spot that receives indirect sunlight.
- Once you notice root growth, usually between 7 to 14 days, you can plant each rooted stem cutting in soil. It's best to give the plant a greenhouse-like environment, such as placing a plastic bag over the cutting. Give it about an hour of fresh air daily. Wait until you notice new, vigorous growth; it can take about six weeks, then transplant it into the ground or a larger container outdoors.
How to Grow Sweet Pea From Seed
Sweet peas are usually direct sown. You can get a jump start on the season by starting seed indoors about four to five weeks before your last frost date. Seed can be started outdoors when the ground has warmed to about 50 degrees Fahrenheit and is not too wet. In the South, you may have better luck seeding sweet peas in the fall to grow into winter.
- Seeds should be scarified by nicking or soaking in water for several hours to soften the seed coating to assist germination.
- They will be easier to transplant if you start them in peat pots.
- Seeds germinate in soil temperatures from 55 to 65 F. Plant seeds in holes about two inches deep. Drop two to four seeds per hole, with holes spaced four to six inches apart.
- Water thoroughly and keep the soil moist until seeds have sprouted.
- When you are ready to transplant, pinch any flowers or buds that may have formed, encouraging root development.
- Pinch the seedlings to encourage vigorous side shoots when the plants reach about 4 inches tall in the garden.
Sweet pea vines have tendrils and will attach to almost any type of support with meshing or strings.
Potting and Repotting Sweet Pea
Sweet peas can also be potted into planters and placed indoors. With just a few steps, you can have a lovely new pea plant for your home.
You must remove the nursery plant from its container and then brush off the excess soil from its roots. After most excess soil is shaken off, place the plant into a larger planter and repot the soil back into it. Feel free to tease the roots if they are clumped together.
When placing the soil into the planter, press down the soil to remove air bubbles for maximum growth.
Few pests or problems are associated with sweet peas, although aphids, mites, and pea moths are occasional pests. Slugs and snails can also eat new plants.
How to Get Sweet Peas to Bloom
Sweet peas need at least six to eight hours of sun daily; the more sun, the better. However, protect the plant from the hot, sweltering sun with shade, if possible; otherwise, it will begin to die back.
Sweet peas also prefer rich soil, so compost-enriched or add bone meal, which adds phosphorus to encourage blooms. Steer clear of fertilizers high in nitrogen that focus more on leaf production than flowers.
Sweet pea flowering time depends on your climate. These plants prefer cooler temperatures and will start to fade in high heat. Areas with cooler summer temperatures can expect flowers in late spring (May or June) or fall (September or October). Warmer regions can expect flowers in winter and spring.
Sweet pea plants are light-sensitive. They come in two types—short-day (fall/winter) or long-day (spring/summer). This day descriptor tells gardeners when the plants bloom. Short-day plants flower during months with shorter days, such as fall and winter. While long-day plants need longer days to initiate buds and blooms, such as after Daylight Savings Time when clocks "spring forward."
How Long Does Sweet Pea Bloom
Sweet peas can bloom for six to eight weeks, depending on the climate. Hot temperatures will cause the plants to decline.
What Do Sweet Pea Flowers Look and Smell Like?
They bear profuse clusters of spring and early summer flowers in various colors, including red, pink, blue, white, and lavender. Sweet pea flowers resemble fringed butterflies, while their sturdy stems appear folded. Their fragrance is sweet, like a blend of honey and orange blossoms.
How to Encourage More Blooms
Encourage more blooms by deadheading or removing spent flowers, so the plant turns its energy to produce more flowers, not pea pods. Also, use fertilizer or amendment that's higher in phosphorus (like bone meal) instead of nitrogen-rich fertilizer.
Caring for Sweet Pea After It Blooms
For Lathyrus odoratus annuals, you do not need to do anything to the plant when sweet peas have finished flowering. Once the hot weather sets in, the plant will naturally die back.
Deadheading Sweet Pea Flowers
Remove blossoms as soon as they fade to keep the plant from forming seed pods. The production of pea pods often triggers the plants to stop flowering entirely. Use sterilized pruners to snip them off or hand-pinch them off.
Common Problems With Sweet Pea
Sweet peas grow easily with suitable environmental factors. However, certain problems can arise if growing conditions are off.
High temperatures are the No. 1 reason for plant decline. However, if you notice buds dropping, check the soil; it should be moist but not soggy. Also, ensure the plant has at least six to eight hours of full sun. Do not give more fertilizer to correct the problem; sometimes, too much fertilizer is the problem.
When a plant is overwatered, it's common for leaves to start turning yellow. Reduce watering or check the soil with your finger to ensure the soil is not waterlogged. Also, giving too much fertilizer can burn the roots, resulting in yellowing leaves.
Does sweet pea come back every year?
Lathyrus odoratus is an annual sweet pea plant that is very fragrant and does not come back every year. Lathyrus latifolius is a perennial sweet pea plant; it is not scented but will return yearly.
What month do sweet peas flower?
Most sweet pea varieties will begin blooming in late spring or early summer (typically May or June). However, in Northern California, sweet peas may bloom later, around September and October.
What do sweet peas attract in the garden?
When is the best time to plant sweet pea?
Sweet peas are a cool-weather plant. Plant your sweet peas in late winter or early spring when soil is workable. These plants can endure occasional late-winter frosts. Also, follow seed packet guidance, especially if you have a long-day or short-day variety since sowing times differ.
Lathyrus odoratus. North Carolina State Extension
Sweet Pea. ASPCA.
Fragrant Sweet Peas Please the Gardener More Than the Bee. Oregon State University Extension Service.
Lathyrus Latifolius. North Carolina State Extension.
Lathyrus. North Carolina State Extension.