Sweet Pea Growing Guide
For many, the scent of sweet peas is what truly captures the essence of summer. The delightful Lathyrus odoratus, or sweet pea, can bloom until the first frost with just a little care and attention. To enjoy abundant flowers early in the season, it’s worthwhile to start pre-sowing and nurturing the plants properly.
Pre-Sowing Sweet Peas
Like many summer flowers, sweet peas benefit from pre-sowing. Seeds are sown in pots indoors to give them a head start before being transplanted to their outdoor growing location. Since temperatures vary by region, the right time for transplanting outdoors depends on your location. Pre-sowing typically requires 4–6 weeks. Seeds can also be sown directly outdoors in their final growing spot as soon as the danger of frost has passed. Direct sowing results in later blooms, but the plants are sturdier since they grow entirely outdoors.
Sowing Sweet Pea Seeds
Before sowing, it is recommended to soak sweet pea seeds. Soaking them in water for 24 hours helps to awaken the dry seeds and activate germination. Remember that seeds can be sown in nutrient-poor soil, such as seed-starting compost. Most seeds already contain the nutrients needed to start growing, and seed compost is gentle on the tender roots of seedlings. Since sweet peas grow long roots, handle seedlings carefully during transplanting. It’s best to sow sweet peas in individual cells so that each seedling can develop in its own space. If seeds are sown in a cluster, roots may be damaged when separating the seedlings.
Allow Germination in Cooler Conditions
Sweet peas germinate best in slightly cooler conditions. Moisture is crucial during germination, so keep the soil evenly moist. When shoots appear, move the seedlings to a cooler spot. Immediately after germination, sweet pea seedlings can tolerate near-freezing temperatures. Cooler conditions help them grow compact and strong. For dense growth, balance temperature and light, and consider supplemental lighting if needed. Higher temperatures require more light, while lower temperatures need less.
Taking Sweet Pea Cuttings
Sweet peas (Lathyrus odoratus) are usually propagated from seeds rather than cuttings, as cuttings often fail to root successfully. However, if you wish to try, it can be done with care and patience. As seedlings grow taller and outgrow the windowsill, you can prune them back, which has many benefits. Cut below the third or fourth pair of leaves, and the plant will develop multiple shoots, resulting in more compact and bushy sweet pea plants. This process, called pinching, promotes denser growth. The cuttings can be used to grow new plants—place them in a glass of water, and roots will often develop quickly, giving you twice the number of seedlings!
Harden Off Sweet Peas
After pre-sowing, you’ll have many seedlings ready for transplanting outdoors. Gradually acclimate the seedlings to outdoor conditions. This hardening-off process involves exposing plants to sunlight and changing weather gradually over a week. Once hardened, sweet peas thrive in rich soil with plenty of sunlight. In shaded areas, growth is weaker, and flowering is less prolific.
Growing Sweet Peas
Sweet peas can be grown almost anywhere—from large gardens to small apartment balconies. When planted in nutrient-rich soil in pots, they bloom for an extended time. Sweet peas can also be grown in flower beds or planter boxes. A planter filled entirely with sweet peas provides enough flowers to cut bouquets throughout most of the summer. When planting outdoors, leave at least five centimeters between seedlings. Sweet pea roots grow deep to access nutrients and moisture. During the first few days after transplanting outdoors, remember to water regularly, as spring and early summer are often quite dry.
Supporting Sweet Peas
Once sweet peas are planted outdoors, they need support. Sweet peas are climbing plants and can grow quite tall, but they still require something to cling to with their tendrils. A sturdy bamboo stick and twine structure is an excellent solution, creating a tipi-like structure. If seedlings are planted in a row, bamboo stakes connected by twine work well. Whatever support structure you use, it should be at least two meters tall.
Fertilizing Sweet Peas
Once seedlings are established in their primary growing location, start fertilizing to promote strong new shoots. Sweet peas are vigorous growers and need plenty of energy. Ensure plants receive adequate and evenly distributed nutrients to encourage growth and maximize flowering.
Regular Trimming
The first flowers typically appear in mid-summer, making it the perfect time to grab your scissors. Cutting sweet pea flowers frequently encourages more blooms. Removing wilted flowers stimulates the production of new buds, significantly extending the blooming period. Few things are as delightful as filling a vase with fragrant sweet peas—just a few plants provide a full vase of flowers throughout the summer.
Tips for Sweet Pea Bouquets
When picking flowers for vases, follow these tips. First, cut flowers early in the morning when stems are full of moisture from the cool night. Place the flowers in water as soon as possible. Before arranging them in a vase, cut new stems with a sharp knife or scissors. Ensure the vase is completely clean, and consider using a flower preservative to keep the bouquet fresh longer. If possible, place bouquets in a cool spot overnight or whenever you’re not at home.
Collecting Sweet Pea Seeds
If you have a favorite sweet pea, you can collect its seeds. Seed collection occurs at the end of the growing season. Allow seeds to develop before the first frost. Once flowers wither, seed pods will form. Label plants to distinguish the ones you wish to harvest seeds from. Record flower colors for planning next year’s planting. Once seeds are ripe, store them in a cool, dry place.
A Perennial Alternative
The fragrant sweet pea, Lathyrus odoratus, is an annual that dies off with the first frost. If you’re looking for a perennial alternative, consider Lathyrus latifolius, or broad-leaved sweet pea. It lacks fragrance but is equally beautiful. Broad-leaved sweet peas can grow up to three meters tall, creating a stunning display from mid to late summer.
