By Julie Pramuk, UC Master Gardener of Napa County

When subtle signs of spring appear in mid to late February, I'm reminded that it's time to start thinking about planting sweet peas. My spring garden is not complete without a row of these fragrant flowers recalling old-fashioned gardens of my youth.

Sweet pea is a flowering plant in the genus Lathyrus and in the Fabaceae family, so it is related to fava beans and other legumes. It is native to Sicily, Cyprus, southern Italy and the Aegean Islands.

The sweet pea became a floral sensation in the late Victorian era. In the language of flowers, a bouquet of sweet peas meant “goodbye” or “thank you for a lovely time.” English gardeners fondly call the sweet pea the “Queen of Annuals.”

Now sweet peas are grown all over the world and found in every color of the rainbow except orange and yellow. Sweet peas bloom from spring to early summer and they prefer cool, moist soil.

Sweet peas can be started early indoors. To do so, place a dampened paper towel flat in a container. Spread the sweet pea seeds on the damp paper towel. Cover the container with plastic film and leave overnight. The next day the seeds should be moist. This process softens the seed coat and speeds up the sprouting process.

At this point, if you wish to start your seeds indoors, fill your seed tray or planting pots with good potting soil. Sweet peas produce abundant roots, so deep four-inch pots are ideal. Sow two seeds per pot, poking the seeds 1/2 inch into the soil, then press to firm the soil. Water carefully so as to not dislodge the seeds, then cover with plastic film to increase humidity and speed up germination.

When your plants are 2 1/2 to 3 inches tall you can plant them in your prepared garden bed outdoors. In the Napa Valley, winters are relatively mild so we can sow sweet peas in late fall.  Recently, while walking to the Napa Farmers Market, I caught sight of a beautiful stand of sweet peas in the Copia growing grounds. I spoke with Jon Brzycki, the Copia gardener. He planted his sweet pea seeds directly into the ground in October.

No matter how you start your seeds, sweet peas are vigorous climbers that can reach seven feet in height. Provide a wire fence or netting for them to scramble up. Sweet peas are happiest with their heads in the sun and their roots deep in cool, moist soil. When possible, plant low-growing annuals in front to shade their roots.

Choose a well-drained site and prepare the bed by applying a thick layer of compost and a natural fertilizer. Mix these ingredients well into your soil. Sweet peas are heavy feeders and require a little more attention to produce abundantly.

Plant your seeds or seedlings six to eight inches apart down the row. Train the vines up the netting or other support. Sweet peas love consistent moisture. Without it, they will fail to thrive.

Feed them throughout the growing season with a light fertilizer. Sweet peas will flower longer if you pick them regularly— a good excuse to have a bouquet in your home or to share with friends.

At the end of their season, usually by early to mid-June, the vines will go to seed and make pods. Although sweet pea pods resemble edible peas, sweet peas are toxic and not edible. If you intend to collect seeds, leave the pods on the vine. If you harvest the pods before they are completely mature, the pea seeds will not germinate. I usually let the vines remain until they are dry and then harvest the pods and bring them indoors.

The dried pods release the seeds quite easily. I leave the seeds out to dry completely and then store them in jars for next year's planting. If you don't harvest the pods, the dried pods will eventually break open and the seeds may self-sow the following fall or early spring. What possibly could be wrong with that?

Sowing a row of sweet peas is well worth the time and effort. Even though I harvest these fragrant, beautiful flowers continuously throughout their growing season, I never tire of them. I'm never ready to say “good-bye and thank you for a lovely time.”

The UC Master Gardeners of Napa County are volunteers who provide University of California research-based information on home gardening. To find out more about home gardening or upcoming programs, visit the Master Gardener website (napamg.ucanr.edu). Our office is temporarily closed but we are answering questions remotely and by email. Send your gardening questions to mastergardeners@countyofnapa.org or leave a phone message at 707-253-4143 and a Master Gardener will respond shortly.