Growing Sweet Peas (Lathyrus odoratus)
The lovely sweet pea was widely grown in English gardens in earlier times and are still more popular there than here. However, if you have a cottage garden some of these fragrant old fashioned beauties are sure to be a hit. If you are into nostalgia or heritage plants sweet peas will also charm you. They are fairly easy to grow and come in a wide range of colors. While sweet peas are related to garden peas, their pods and peas shouldn’t be eaten but only admired.
Sweet peas are native to the Mediterranean and Aegean Islands. The wild sweet pea is lavender in color and fragrant but early English and Scottish gardeners worked with the plants to develop a wide range of colors and to intensify the fragrance. Cultivated varieties also have larger flowers than the native plants. A Scotsman named Henry Eckford, was famous for developing many sweet pea varieties and starting a craze for exhibiting the plants in the late 1800’s and early 1900’s.
In Victorian times sweet peas were widely grown for bougets and they are still grown in greenhouses for the floral trade. White sweet peas are often found in late spring and early summer wedding bougets. In the language of flowers the sweet pea signifies blissful love. But sweet peas do well in the garden also.
Sweet peas have spade shaped leaves of blue-green to gray green. Each leaf consists of two leaflets, which look like a pair of leaves on opposite sides of the stem. Stems can look flattened or ridged. Stems also have tendrils which wrap around a support to pull the plant up and into the sunlight. The flowers are typical of the pea family. They have two larger, backswept petals, two smaller petals in front and another petal in front of them which is tube like and curled toward the back. Cultivated sweet peas come in almost every color except yellow, from white to scarlet, shades of blue and purple, and interesting cocoa and other colors.
How to start sweet peas
Gardeners will almost always start with seeds, rarely one may find small plants offered at a nursery. Sweet Peas can be planted where they are to grow early in the spring. In zone 5-6 mid-to late April is usually best. They take 75-85 days from germination to bloom. To get them growing well in time to beat the heat of summer some gardeners start them in pots inside 2-4 weeks before planting is feasible outside. A cool greenhouse or cold frame can work. In warmer climates they are often seeded where they are to grow in the fall and they sprout and bloom in early spring.
Sweet peas don’t transplant well, so they should be started in pots that dissolve, only a few weeks before they can be transplanted outside. You want to disturb the roots as little as possible and the plants should only have 2-3 sets of true leaves. Paper pots work well. Peat pots or Velcro pots that open are other ideas.
Whether you start them inside or outside the seeds need to be soaked in warm water for a few hours and then nicked for the best germination. A pair of toenail clippers works well for nipping the seed coat. You only want to crack the coat or take a small bit out on the side away from the seed scar. This allows moisture to penetrate the seed coat and stimulate the seedling to begin growing. Seeds treated this way should germinate in 7-14 days. If not soaked or nicked germination can take much longer.
The trick to growing sweet peas is the timing. Sweet peas like cool weather but don’t survive hard frosts. They are a cool weather annual, that needs to be started early for early summer bloom. When summer turns hot they fade and die. But if you allowed pods to form and dry you can collect seeds for the following season.
Sweet peas are a vining plant and need to be trellised, staked or grown against a fence. They range between 3-6 feet in size depending on variety. They will grow in full sun to light shade and in almost any soil, but the area must be well drained. Fertilizer generally isn’t needed. Don’t crowd them as this tends to increase powdery mildew. Space them 6-8 inches apart.
Sweet peas will flower for a longer time if the dying blooms are pinched off and not allowed to make pods. Some people also pinch the ends of growing stems when they reach about 3 feet long to encourage side growth and bushier plants.
One of the best ways to display sweet peas in the garden is on a fence or trellis where later blooming vines will take over and cover the dying foliage and continue the bloom. Good pairs are hyacinth or scarlet runner beans, cypress vine, morning glories and moon flowers. Some people make teepees for them or allow them to climb up suspended strings.
Other problems for sweet peas other than powdery mildew are snails and slugs in some places. Deer and rabbits will also eat sweet peas. Grown inside aphids can be a problem, but in the garden that isn’t usually a problem.
Varieties of sweet pea
While there are perennial sweet peas offered, (usually Lathyrus latifolius) the full range of color and fragrance is only realized in the annual varieties of sweet pea, Lathyrus odoratus. Wildflower and native plant companies sometimes offer vetches and similar pea type plants that are US natives but they should not be confused with sweet peas. Occasionally garden sweet peas re-seed and turn up in odd places but that is rare in zones 5-6.
Some varieties of sweet peas that are easy to find include; ‘Old Spice mix’, ‘Mammoth mix’, ‘Knee High mix’,( shorter stocky vines) ‘Royal mix’, ‘Elegance series’- (single colors are often offered in this series), and ‘Spencer Ripple Mix’, bi-colors and streaked flowers. There are some older, rarer varieties still being grown but they can be hard to find. Some places offer dwarf sweet peas, these grow about 2 feet long. Two seed catalogs that carry sweet pea seeds are Johnny’s Seeds (www.Johnnyseeds.com ) and Pinetree Garden seeds,www.superseeds.comYou can save seeds if you allow the pods to dry and ripen on the vine, then collect the peas and save them in a dark, cool place. The flowers probably won’t look like the parents but will be pretty.
Don’t eat sweet peas
While sweet peas may resemble garden peas they are not good to eat. Some people giving out sweet pea growing advice confuse the flowering sweet pea with edible peas and this isn’t a good thing. While you may not feel sick immediately the sweet pea contains substances that inhibit collagen formation and may cause neurological and muscle problems. Sweet pea consumption has been linked to aortic aneurysms also. The illness caused by sweet pea consumption is called Lathyrism. Animals should not eat the seeds either.
Why not try some sweet peas this spring in your garden? They make long lasting, sweet smelling cut flowers and can provide a pretty vertical accent in early summer. The sweet pea is a flower that all gardeners should try at least once in their lifetime.