The sweet pea (Lathyrus odoratus) became a mainstay of the Victorian cutting garden because of its delicate flowers and its heady perfume. As with modern-day hybrid flowers, today's sweet pea varieties possess little fragrance, having lost one of their finest qualities in the breeding process. Martha grows heirloom varieties of this annual vine - 'Lord Nelson,' 'Mrs. Collier,' 'Flora Norton,' and 'Painted Lady' -- that still retain their charming scent. All sweet peas are descended from a fragrant wild flower native to Sicily, first recorded by Father Francis Cupani in 1697.
Because sweet peas perform best in cooler temperatures, sow the seeds in very early spring, before the ground temperature reaches 40 degrees. Where you live determines when you should plant sweet peas: for most areas of the country, February through April; in California, August to September if you want an early spring bloom, November to December for summer bloom; in the Southwest, southern Texas, or southern Florida, September to October; for the lower southern states, November to January.
For best results, soak the seeds in water before sowing; treating seeds with a dose of inoculant powder before planting will increase the crop's yield. You won't need to use much inoculant for it to be effective, but you can't use too much -- it's harmless. Plant sweet peas in a sunny spot and in compost-enriched soil with good drainage. (Be aware, though, too much nitrogen in the soil results in viney plants with few pods.)
Erect slatted folding trellises about four feet high to support the plants while they grow. You can also make trellises from netting stretched between posts or twiggy tree branches saved from pruning. Use a garden reel to mark the rows with string. Then use a hoe to make trenches for planting. Sow the seeds thickly (about an inch apart). Water well, about one inch a week, and keep the soil moist throughout the growing season. Fertilize every two weeks with organic fertilizer or manure tea. Cut flowers every few day to encourage continuous blooming.