Sweet peas (Lathyrus odoratus) are cherished for their delicate, ruffled blooms and intense, sweet fragrance. While traditionally grown in garden beds, cultivating them successfully in containers requires specific techniques to manage their vigorous root system and feeding requirements. Growing sweet peas in pots allows gardeners with limited space to enjoy their beauty and scent on patios, balconies, or small decks. Tailored care is key to maximizing their colorful and fragrant display.
Preparation and Selection
Selecting the right variety is the first step toward a successful container display, as not all sweet peas are suited for pot culture. Highly vigorous climbing varieties quickly outgrow containers, so choosing dwarf or semi-dwarf types is recommended. Look for names like ‘Cupid,’ ‘Bijou,’ or ‘Little Sweetheart,’ which are bred to remain compact, typically growing only 10 to 18 inches tall. The container choice is paramount because sweet peas develop a long taproot.
A container should be a minimum of 12 inches deep and 10 to 12 inches in diameter to provide adequate root volume. Deeper pots are preferable, as they help keep the roots cool and prevent rapid drying. Excellent drainage is mandatory, so ensure the container has generous drainage holes. The potting medium should be a high-quality, peat-free, well-draining mix, not garden soil, which compacts too quickly. This specialized mix offers the necessary aeration and moisture retention for a container-bound root system.
Sowing and Initial Growth
Sweet pea seeds have a hard outer shell that delays germination. To speed up uniform sprouting, pre-treatment is highly beneficial. Gardeners can gently nick the seed coat using fine-grit sandpaper (scarification) or soak the seeds in room-temperature water for 12 to 24 hours. Seeds that swell should be planted immediately.
Start seeds indoors six to eight weeks before the last expected frost date. Sow two or three pre-treated seeds per cluster, planting them one-half inch deep into the potting mix. Place the pots in a cool, bright location, ideally around 50°F (10°C), to encourage strong root development. Once seedlings reach about four inches tall, gradually acclimate them to outdoor conditions over a week (hardening off) before moving them to their final sunny spot.
Care, Feeding, and Support
Container-grown sweet peas require more attentive care than those planted in the ground, especially regarding water and nutrients. Due to limited soil volume and exposure, pots dry out rapidly, often necessitating daily watering during warm periods. Consistent, deep saturation is necessary to keep the root zone evenly moist; drying out stresses the plant and causes buds to drop. Sweet peas are heavy feeders because nutrients in the potting mix are quickly depleted.
Once plants set flower buds, they benefit from regular applications of liquid fertilizer. This feed should be high in potash (potassium) to promote abundant flowering, but low in nitrogen, which encourages leafy growth over blooms. A diluted tomato fertilizer, applied every one to two weeks, serves this purpose well. Even dwarf varieties benefit from support; install a small trellis, cage, or tripod structure within the pot. This allows tendrils to climb and keeps foliage off the moist soil, improving air circulation.
Maximizing Bloom and Season Extension
The most effective technique for a prolonged flowering season is the consistent removal of spent flowers, known as deadheading. If faded flowers remain, the plant redirects energy toward setting seed pods, signaling the end of its life cycle and halting new production. Harvesting sweet peas for bouquets accomplishes this goal; the more flowers cut, the more the plant is stimulated to produce. Cut stems as long as possible, right back to a leaf joint, and harvest them in the cool morning for the best vase life.
To encourage a bushier plant with more flowering side shoots, pinch out the growing tip when the young seedling reaches about six inches in height. Pinching redirects growth hormones, forcing energy into lateral branching rather than a single main stem. Monitoring for common pests, such as aphids, is also important, as they quickly colonize new growth. A strong jet of water or organic insecticidal soap can manage small infestations, keeping the sweet peas flowering healthily.