Last Updated on September 15, 2022 by Plant Mom Care
Lathyrus odoratus or the sweet pea, a flowering plant from the genus Lathyrus of the Fabaceae (legumes) family, is native to the Aegean Islands, Sicily, and southern Italy at present, hundreds of varieties have been developed and cultivated by gardeners and the horticultural industry.
These plants have been cultivated in gardens since the 1600s. Henry Eckford, a Scottish nurseryman, worked on crossbreeding and developing several hybrid cultivars of their modern forms in the late 1800s.
It is an annual climbing plant, reaching heights of 6-8 feet, with suitable support. It has two pinnate leaves with a tendril, which can twine around plants and structures and help the plant climb.
The flowers look like fringed butterflies and are purple and ¾ – ½ inch broad in wild plants, while they are larger and variable in many hybrid cultivars and grow in colorful clusters of pink, red, lavender, blue and white with a strong fragrance. The seeds are housed in a hairy pop about 2 inches long, splitting open when it dries to spread the seeds.
Older varieties were chosen for both their effervescent colors and strong fragrance. Several modern hybrid cultivars sold these days come in several more shades except yellow, but not many of the newer varieties are as fragrant. Currently, efforts are being made by cultivators to develop plants with yellow flowers without any success.
These beautiful and fragrant plants are popularly grown in gardens and parks. It is often seen growing on trellises or fences but is comparatively easy to cultivate in containers or hanging baskets to spill down the sides.
Cultivating these plants in vegetable gardens helps to attract bees along with other pollinators. They can also be grown with pole beans. However, these plants are vulnerable to ethylene-producing plants and shouldn’t be grown near fruit trees.
Sweet Pea Light Requirements
They thrive under full sun, although they need some afternoon shade in warmer climates.
Sweet Pea Watering
These plants need watering every week to keep the soil damp during their growing season. Plants growing in warmer weather might need extra water, particularly in summer.
Sweet Pea Humidity
These plants can tolerate a variety of humid conditions.
Sweet Pea Temperature
They prefer a temperature range between 55-65°F. They can tolerate a little frost, but don’t like very hot temperatures and stop flowering when the temperature rises above 65⁰F.
Plant them at the start of spring to enjoy the flowers before they wither in summer. They need 50 days of temperatures under 60⁰F to flower well.
Sweet Pea Soil
They prefer rich soil that drains well and a slightly alkaline pH of 7.5. Add compost if the soil is of poor quality.
Sweet Pea Repotting
Repotting these plants is unnecessary as they are annuals. However, several plants can successfully be grown together in containers, provided the containers are large enough – 5 gallons is the minimum. Their root systems grow large, so only a maximum of 8 plants grow together in a container of that size, as they can easily get root-bound.
Sweet Pea Propagation
They are usually sown directly in gardens or containers. Scarify the seeds by nicking and/or by soaking in tepid water for some hours to soften the coating. Seeds can be planted outdoors when the ground warms up to about 50°F and is not very wet, you could also start seeds indoors during winter in peat pots to start early; however, in warmer areas, the seeds can be planted outdoors or started indoors in the fall. When the plants grow to about 4 inches tall, nip off the top to promote branching and more flowering.
They need steady and regular monthly feeding during their growing season. Use a fertilizer with more potassium, like a tomato fertilizer.
Most varieties will start flowering in late spring or so, forcing the plants into producing more flowers by harvesting the flowers for flower arrangements and deadheading spent flowers.
Sweet Pea Common Problems
Damping-off usually happens when plants are grown from seed. What happens is the seedling appears to be growing well but then it suddenly withers and dies. This is due to a fungal infection affecting the seedling when the soil is excessively damp and temperatures are more than 68°F or if the fertilizer contains excess nitrogen.
Seedlings need water but the soil also has to have a good draining capacity and mustn’t be over-fertilized. Avoid overcrowding and space out the seeds when planting to ensure the plants will have good air circulation.
Downy mildew is initiated by a fungus that creates white/grey areas on the leaves. Avoid watering the plants overhead and ensure the plants have good air circulation. Don’t work near the plants when they are wet.
Several pathogens can initiate root rot in seedlings and mature plants. Make sure you don’t over-water and discard affected plants.
Several types of fungi can cause diseases that create rust or brown spots on leaves and stems. Remove infected plants and treat nearby plants with a fungicide.
Aphids often transmit disease when they attack the leaves and suck sap from them. They also produce a sweet liquid that attracts ants; they can be washed off with water or treated with insecticidal soap.
Leafminers bore inside the leaves and cause irregular twisting lines. The adults are tiny yellow and black flies and their larvae are yellow maggots, they don’t generally kill the plants but can disfigure the leaves, remove affected foliage and keep the areas around the plants clear of debris.
Slugs chew out large holes or eat whole leaves leaving a slime trail, generally attack the plants at night, and are usually a problem in wet weather. Handpick them off the plant at night and place a barrier of diatomaceous earth to prevent them from crawling over near the plants.
Spider mites are minute pests and maybe red, brown, black, or yellow. They suck on sap and remove chlorophyll and inject toxins that create white dots on leaves, making the foliage yellow and dry. They can multiply fast in dry conditions. Insecticidal soap will control them.
Thrips are tiny black or yellow insects that suck the sap of plants and attack the flower and foliage, leaving a mottled, discolored spot or silvering on leaf surfaces. They can spread several diseases between plants. Remove weeds near the plants and clear away debris. Treat the plants with a suitable pesticide.