To germinate sweet peas, soak seeds in water for several hours to soften before planting, suggests Brad Allen of Fleur Jardin, a Newport Beach landscape maintenance firm specializing in providing seasonal color.
Then position the plumped-up seeds in furrows 3/4-inch to one-inch deep, spaced one inch to two inches apart. Plant directly in the garden, amending the soil first, if necessary.
Or do what Allen does and start the seeds in nursery flats filled with potting soil. "Find flats with the smallest openings in the bottom you can," he suggests.
Place the flats where they will get at least a half day of sun, he says, and preferably set on block for snail protection. Keep the soil moist.
When the young seedlings' first set of leaves develops, pinch them back and let second shoots develop. "This makes the plants stronger," Allen says.
Transfer the seedlings to the garden when they're about four inches to five inches tall and plant them 10 inches to 12 inches apart. "Closer is not better," Allen says. Or, if you planted directly in the soil, thin out your seedlings accordingly.
Provide string netting, wire, or a trellis as soon as tendril form on the plants to provide the vines support. If you plant "Bijou," "Knee-Hi," "Jet Set' or another bush-type variety, no support will be necessary.
Water sweet peas well and frequently and fertilize with half-strength water-soluble fertilizer every other week once they are well established, Allen recommends. And cut the fragrant flowers to your heart's content, knowing you're only motivating to plants to produce more.
"Once you've had success with germinating seeds--and you're almost guaranteed to with sweet peas--it becomes a tremendously satisfying, almost ritualistic thing," Allen says. "It's becomes part of the process of getting ready for spring."