Over the centuries, sweet peas have garnered the reputation of being the divas of the cottage garden: difficult to germinate, slightly finicky, and tough to grow. While there may be a grain of truth to this, sweet peas can still make a wonderful outdoor addition when the conditions are right.
Sweet peas (or Lathyrus odoratus) are native to Sicily and have been grown in gardens since the British horticulturist Henry Eckford began cross-breeding them in the 17th century. Since then, these plants have become famous for their delicate flowers, intoxicating scents, and pastel shades. Modern varieties are available in several colors, including white, blue, purple, red, and pink. Some sweet peas even feature beautiful bi-colored flowers. While some varieties only give off a subtle scent, most boast a full-bodied, sweet, and sensuous perfume that's difficult to duplicate.
Why Plant Sweet Peas
While most plant enthusiasts would agree that sweet peas are beautiful, the special care required to start them from seed can be intimidating to new gardeners. Still, those who've made the effort will tell you that sweet peas have added color, fragrance, and overall visual interest to their gardens. Plus, they flower profusely, making it easy to create a ton of bouquets for you and your friends, family, and neighbors to enjoy! Sweet pea flowers continue to fill a room with their heavenly scent long after they’re cut — especially if you cut them in the morning when the aroma is at its strongest and sweetest.
Although they can technically grow anywhere, sweet peas tend to do better in places with cooler weather. Specifically, they prefer mild winters and cooler summers. Sweet pea seeds have to be sown in cool weather, and their flowers typically bloom right before the temperature starts to climb.
How to Grow Sweet Peas
Sweet peas are annual plants and will readily self-sow. The flowers go to seed if left uncut and form pods that vaguely resemble the pods of edible peas. While they are similarly shaped, sweet pea pods can be distinguished by their fine, white "hair."
Unless you’ve saved seeds from the previous year’s flowers, you’ll likely have to purchase some from your favorite local or online seed retailer. If fragrance is one of your top priorities, consider growing heirloom varieties that bear a more traditional scent, such as Cupani (the original sweet pea) and Butterfly Old Spice. Painted Lady, a bi-colored variety, features pink and white flowers that emit a strong scent. If you're looking for unique colors, check out Henry Eckford, Electric Blue, and Velvet Elegance, but remember that these varieties may not be as sweet-smelling as others. While sweet peas are great attention-stealers, they can also complement some of the showier blooms in your garden. For example, Dorothy Eckford is a sweet pea variety that produces subtle white flowers. Just imagine how they would look alongside some vibrant plants and flowers.
Sowing your sweet pea seeds will require a bit of preparation, but it’s more than worth it. Pre-soak the seeds for 24 hours, and nick the surface each one with a sharp blade. Although sweet peas are traditionally sown in the fall, people who live in colder climates (zone 7 or colder) might want to plant them in the late winter or early spring before the last frost. Sow the seeds in indoor pots to get them off to a great start before planting them outside. Be sure to harden the seedlings off for a week or so and place them in the garden when the soil is warm enough to work. When it comes time to plant, dig a trench about four inches deep and use a dibber or pencil to create small holes in which to drop the seeds.
In milder climates, you'll want to plant sweet pea seeds in the fall. Although you’ll have to wait all winter to see your first blooms, your plants will have developed a strong root system and begin to explode with delicate flowers by the early spring. Flowers often last throughout the summer if you live in a cooler area like the Pacific Northwest, where I live.
Helping Your Sweet Peas Thrive
Regardless of when you sow, be sure to prepare the soil with compost or finished manure. Sweet peas need fertile, loamy, well-drained soil to thrive, as well as plenty of sunshine. You'll also want to protect the seedlings from slugs, birds, and other pests that may see them as tasty treats. Create a barrier around them using cloches or the small plastic produce baskets from cherry tomatoes, berries, and strawberries you’ve purchased at the supermarket.
Sweet peas are vining plants that can grow up to 10 feet tall, so be sure to give them plenty of support using trellises, fences, arches, or bamboo stakes. If you prefer the plants to bush out, pinch the tops of their sprouts when they’re approximately six inches tall. Once flowers begin to appear, you'll want to regularly deadhead the plants to encourage more blooms. The more you harvest, the more they'll produce! However, sweet peas love cool weather and may start to produce fewer flowers when the temperature reaches above 70 degrees.
To keep your plants and flowers as healthy as possible, don’t let the soil dry out. While sweet peas don’t exactly like having "wet feet," they definitely won’t grow well if the soil is dehydrated. To prevent this from happening, try planting some low-growing flowers or plants at the base of each sweet pea plant.
If you want to save a few seeds for next year, leave the flowers on the vine until they've had enough time to form seed pods. If the pods burst, they’ll often self-sow the following year. If you want more control over this process, simply collect the seed pods when they’re full.
Pests and Diseases to Watch Out For
Sweet peas can be damaged by a variety of pests, including caterpillars, aphids, and greenflies. The latter have even been known to spread mosaic virus. Pollen beetles can also create problems for sweet pea flowers, and, as mentioned above, slugs and snails can terrorize young seedlings. Sweet peas are also susceptible to diseases such as powdery mildew, Pythium root rot, gray mold, and rust. Luckily, you can prevent bug infestations and diseases by protecting your seedlings, watering them correctly, and promoting good air circulation as they continue to grow.
Sweet peas are beautiful and rewarding plants to include in your garden. Although they may need special attention when they're young, the wonderful scent and bountiful bouquets they produce are worth the effort.