CORVALLIS - Ever since Keats described sweet peas, with their "taper fingers catching at all things, o bind them all about with tiny rings," the English have been mad for the tendrilled vines.
Sweet peas are a classic flower in English gardens since they were introduced in the 17th century from southern Italy. The first sweet peas had relatively small flowers but possessed a powerful and attractive fragrance. The peas themselves are inedible and even toxic if ingested in quantity.
"Oddly, sweet pea flowers naturally self-pollinate while still in bud, and it would seem that their color and perfume are there to please the gardener more than the bee," said Ross Penhallegon, horticulturist with the Oregon State University Extension Service.
Sweet peas flourished in English gardens, and have transplanted well to all parts of the world, especially throughout Oregon, he said.
Shorter bush or dwarf varieties, including "Supersnoop" types, make a colorful hedge in a flowerbed, along a walkway or in planters. Taller climbing varieties, such as "Old Spice Mix" or "Royal Family" can be trained to cover fences and trellises.
"Both types make wonderful cut flowers with sweet, old-fashioned fragrance with a variety of colors," Penhallegon said.
Sweet peas grow best when planted during the early spring in western Oregon and a little later in the higher elevation areas east of the Cascades. Sweet peas are susceptible to powdery mildew, a fungal disease that can infect crowded plants or those growing in damp shady places. They may also suffer from pea enation, a mosaic virus that can develop in the heat of summer. Some varieties are powdery mildew resistant.
The best way to avoid these diseases is to plant sweet peas in a well-drained, sunny location with good air circulation before mid-March and to protect the seedlings from frost.
To ensure success, Penhallegon recommends preparing a 10-inch deep trench, filled in halfway with well-rotted manure or compost. Top off the trench with soil mixed with a small amount of super phosphate or bone meal, a well-balanced fertilizer such as 15-15-15, or other organic fertilizer.
Plant the seeds 3/4 to one-inch deep, spaced two inches apart. Germination may be quicker and more uniform if the seeds are soaked for 24 hours just before sowing. Slugs can be a problem, so take precautions before planting.
Seedlings should be thinned to five or six inches apart. When the seedlings are about four inches tall, pinch off the tip of the stem above the topmost leaves to help create a bushier plant with several flowering branches. As the plant grows, mulch around the base to keep the ground cool.
Water when needed and remove the spent flowers before they set pods. By removing the spent flowers, sweet peas should blossom all summer with long-lasting, sweet-smelling bouquets.