Lathyrus odoratus; photo courtesy of Flickr cc/Steven Depolo
Lathyrus odoratus is the only scented species of the Lathyrus genus, which consists of more than 150 species. The first wild sweet peas may have been found in Sicily and Malta, or China and Sri Lanka. But in 1695, Francisco Cupani recorded the sweet pea as first seen in Sicily. He gave it the rather effusive name of Lathyrus distoplatypylos, hirsutus, mollis, mango et peramoeno, flore odoro. You can still get the 'Cupani's Original' (or sometimes named 'Original') from flower seed companies today. The first sweet pea was offered for sale as 'sweet scented pease' in 1724. Called 'Painted Lady', it was a pale red.
By 1778, sweet peas were offered in white, scarlet, and purple, and in 1793 a "black" form was bred. The black color was probably a dark purple or maroon. At that time, sweet peas grew only three to four feet high and had just two flowers per stem. Today, multiflora types can have up to 11 flowers, or more commonly 4 to 8 flowers on a stem. Colors have been improved by breeders. Purer whites have been developed, as well as colors of every shade of pink to orange to red, including shades of blue and lavender.
The search for a perfect yellow sweet pea goes on. Breeders make constant improvements, producing robust climbers and tough growing dwarfs, while still maintaining the delightful fragrance of the original species.
Sweet Pea Growing Essentials
Here is a list of useful growing tips so you can grow the perfect sweet pea!
Seeds are toxic if consumed. Keep out of reach of children and pets.
Soil pH at neutral to alkaline.
Amend the area with compost or well-aged manure in fall; this will condition the soil.
Sow seeds in pots and place in a cold frame or greenhouse during October or else sow in containers indoors between January and March for spring planting outdoors. Spring-sown plants will be three weeks later than autumn-sown plants.
To provide good seed germination, nick the seed coat with a nail clipper or use sand paper to penetrate the seed coat, but don't overdo it. This is especially needed for mottled and black-seeded varieties. Soaking seeds overnight is not advised and may prevent germination. White, brown, and wrinkle-seeded varieties should never be nicked.
Sow five to seven seeds per five-inch container filled with a sterile potting mixture.
To prevent rotting of soft-seeded varieties in containers, add extra peat and perlite or horticultural sand to the sowing medium.
When planting seeds, water immediately after sowing and refrain from watering until seedlings emerge. Do not overwater seedlings.
Repot seedlings into three-inch pots before the first leaves begin to open
Pinch out the growing tip once seedlings have grown two pairs of leaves. This will encourage side shoots and bushier plants.
Prepare an outdoor garden area about three feet wide. Cultivate the soil until fine and crumbly to the touch. Early autumn is a good time to amend soil with compost and/or manure.
In spring insert a row of eight foot bamboo canes 18 inches apart along the prepared garden area. Attach string or twine to the bamboo about every three inches for seedling tendrils to climb up. From mid-March to mid-April, plant seedlings along supports.
Sweet-pea seedlings can take a light frost.
Proper placement of seedlings in the garden is essential. Bright light without too much hot direct sun is best. Don't plant in shade of overhanging tree branches. Do not place on a fence or wall with direct hot sun.
Mulch plants after planting to conserve moisture. Drip irrigation will work fine.
Sufficient light and rain must be available, but too much sun and heat can encourage mildew.
Tendrils can only grow on string, twine or netting that is not thicker than 1/4 inch thick in diameter.
Sweet peas can be grown as trailing plants in large containers, making a waterfall of color.
Protect large plantings from birds by using highly reflective Mylar ribbon or netting.
To conserve soil moisture around plants, mulch with grass clippings. Spring plantings will need more water as days grow longer and warmer.
Fertilize with manure tea or organic plant food monthly
Cut flowers every few days to promote continuous new blooms. Deadhead spent blossoms to extend the flowering time and to prevent plants from going to seed, if preferred.
Replace damaged seedlings with young seed plants, as they will soon catch up.
Gardening with Heirloom Seeds by 
