Description

• Perennial sweet pea (Lathyrus latifolius) is a tall, vining plant with flowers in shades of red, purple and pink. Unlike the more familiar annual sweet pea, this perennial cousin is not fragrant. It grows in moist, well-drained soil. It grows 4 to 8 feet tall and attaches to its support by curly tendrils. Blooming in June and July, it doubles the sweet pea season when following the annual species. It grows in U.S. Department of Agriculture zones 4 through 7.
  
  

Culture

• Give this perennial a sunny, well-drained site. Compost or leaf mold mixed into the soil before planting ensures good drainage as well as moisture and nutrient retention. Like most sweet peas, the perennial should be be staked so it has something to climb on. Temporary trellises made of stakes and jute twine are ideal. So do bamboo tepees. Water when the top of the soil gets dry. A single fertilization in early spring with a balanced fertilizer -- 8-8-8, for instance -- is all that is needed.
  
  

Problems

• Perennial sweet pea is easy to grow and has few insect and disease problems. While it prefers evenly moist soil, it tolerates moderate drought. The plant will let you know when it's drought-stressed by wilting. Water deeply when the top of the soil is dry and use 2 inches of mulch to conserve moisture and shade tender roots. Refrain from overhead watering to keep the plant dry and mildew free.
  
  

Companion Perennials

• Brazilian verbena (Verbena bonariensis), also known as tall verbena, grows 4 feet tall and has bare stems and little lilac clusters. It makes an impact in front of sweet pea because it's easy to see through. If you'd like to compensate for perennial sweet pea's lack of fragrance, plant oriental lilies in shades of white (Casa Blanca) and pink (Star Gazer). Lavenders in different sizes add a spicy, sweet fragrance and strong texture with their gray mounds and spiky flowers. Plant them in the front and middle of the perennial border.