Let your annuals seed themselves
By Oregon State University Extension Office 
CORVALLIS, Ore. – If you let nature take its course, it will sow next year’s annuals in a “Darwinian” garden. Instead of planting flowers every spring, you can let some of your annuals go to seed each fall, explained Barb Fick, Oregon State University Extension horticulturist.
Self-sown seedlings will come up in the fall or early spring, when and where they are best suited to grow. Then, you can thin these annual flower seedlings to allow survival of the fittest and to sculpt the lines of color in your garden.
“In other words, plant where you want flowers, and thin out where you don’t. Let serendipity play a role,” Fick said.
Sweet peas, sunflowers, calendula, nasturtiums and annual delphiniums make perennial appearances in Oregon gardens. Bread seed and Shirley poppies, Clarkia, alyssum, even petunias will come back year-to-year, depending on winter’s severity.
Herbs and greens such as lettuce also are willing self-sowers. Dill, fennel and cilantro may come back every year from seed heads left to overwinter.
Annual plants are programmed by nature to set seed in one year, Fick said. Most of the summer we deadhead and fertilize annuals to keep them blooming and to postpone seed development.
“But come September, try the Darwinian approach, by letting meticulous care go. Allow a few of your annuals to go to seed. Let the flower heads dry and droop. The wind, the birds and the plants themselves will scatter ripe seeds.”
Some cultivars will not come back the following year “true to type” because hybrids do not produce uniform offspring. “For most people, that isn’t a problem.” Fick said. “It means that instead of a pure stand of all-white alyssum, you may see splashes of purple. That’s serendipity.”
A word of warning: Beware of fennel. “It has become a noxious weed, and I would not recommend that anyone plant it,” Fick said. “I made that mistake and I keep pulling out fennel.”
By: Judy Scott
Source: Barbara Fick