Sweet pea (Lathyrus odoratus) is a captivating annual plant that produces vivid flowers as well as an enticing aroma. It makes a showy addition to any border garden, trellis, or potted arrangement. The climbing nature of sweet peas makes them an ideal choice for adding visual height to your landscape.
These delicate flowers are quite hardy, but it can take a bit of skill to grow them successfully.
Grow your sweet pea from seeds in the winter. Promote sprouting by placing the seeds in a damp paper towel. In a small pot or seed tray, place nutrient-rich potting compost and add two sprouted seeds per pot, pushing them down until they are 3 cm below the surface. Place the pots along a windowsill, and the sweet peas will sprout in 10 to 14 days.
A month after germination, transfer them to a larger pot and continue growing indoors until April or May, then transfer them outside.
For the best results, plant your sweet pea seedlings in high-quality alkaline soil. Place each one 7 to 8 inches apart to allow space for them to grow. When you transfer them from their indoor pots, remove the plant with the full root system intact to avoid damage.
For container planting, choose a pot that’s between 10 and 16 inches wide to accommodate the roots. You may want to put a trellis or other structure nearby to give the sweet pea support as it climbs.
Sweet peas love to bask in the morning sun and should receive about six hours of sunlight daily. Try featuring them in a place that receives full bright sunlight in the early and middle part of the day and shade in the afternoon when temperatures reach their peak.
This is especially important in warmer climates; sweet peas may begin to fade when temperatures climb above 65 degrees Fahrenheit.
Sweet peas are susceptible to root rot, so take care not to over-water them. If you’re getting a lot of summer rain, only water the plants if the soil is dry about one inch down.
When they do need water, it’s best to water them at the soil level in the morning to give the plants the moisture they need while allowing time for the warm part of the day to dry up some of that water.
Sweet peas prefer well-drained and nutrient-rich soil. If you mix in aged manure, your plants shouldn’t require additional fertilizer. If you don’t have aged manure, try using a potash fertilizer to make the sweet peas more drought resistant.
Nitrogen and phosphorous fertilizers can encourage larger plants and more flowers in many species, making them ideal for mixed flower beds that include sweet peas.
Sweet peas prefer cooler climates and do well in USDA hardiness zone 7 and lower. If you live in zones 8 through 10, try planting your sweet peas in November instead of spring to take advantage of the cooler months and promote a period of flowering that will last throughout the winter and spring.
Promote flowering with proper pruning throughout your sweet pea’s life cycle. As it grows, remove any dead leaves or branches. Snip off seed pods when you find them. If they go unattended, your sweet peas won’t produce many flowers.
Use sharp snips and prune at a 45-degree angle, as jagged cuts can invite disease. Finally, prune any areas that do display signs of disease to prevent the spread of infection.
Sweet peas are grown in part because they make such a beautiful addition to floral arrangements. Pick your sweet peas when there are still a couple of unopened flowers near the tip of the stem — they will last longer in the arrangement as they continue to bloom.
Adding floral food to your vase will help keep cut sweet peas flowering for longer.
Propagating sweet peas is easy. Simply cut a branch and dip the end in a bit of root hormone before placing your cutting in water. Once roots appear, you’re ready to put the new plant in soil. Propagation is a great way to spread the visual impact of sweet pea across your yard.
Sweet peas are prone to a variety of diseases, including blight, mildew, rot, rust, virus diseases, leaf spot diseases, and pea enation mosaic. The best way to protect your plants is to maintain a clean garden and water regularly. If your plants look unhealthy, a good fungicide can cure many of these diseases.
It’s also important to trim away any parts of the plant that show signs of disease.
Pea plants are susceptible to insect infestation at almost any stage of growth. Aphids, caterpillars, leaf miners, snails, slugs, and spider mites top the list. Keep them away from your sweet pea by spraying insecticidal soap on the leaves as per the manufacturer's instructions.
The delicate and eye-catching sweet pea flowers are show-stoppers while they’re growing outdoors and in your favorite vase after harvest. These vining plants are ideal for the back row of an ornamental garden where they have a trellis or other structure to climb. They also thrive in containers with poles and trellises.
Eastern redbud (Cercis canadensis) has pink flowers that look like sweet pea flowers. The major difference is that the leaves have a slightly different shape to them, and the stems are not quite as prickly.
While sweet pea is a member of the legume family, all sweet peas plants are toxic. Eating them in large quantities can result in a condition called lathyrism, which can lead to paralysis and convulsions. For this reason, consider alternatives to sweet peas if you have pets or young children that may try to ingest the plant.
Sweet peas are available in many varieties, allowing you to showcase white, light pink, purple and even fuchsia blooms in your garden. The vast majority of sweet pea varieties are annuals, but Lathyrus latifolia is a perennial.