Sweet Peas Won't Germinate

Temperature

• As a cool-season flower, sweet peas need a soil temperature between 55 to 65 degrees Fahrenheit to achieve germination -- whether started indoors or out, sown in the spring or fall. Start planting your seeds up to six weeks before the last frost date. Sweet peas tolerate light frost.

Indoors

• Starting your seeds indoors gives you a chance to get ahead on growing when the outdoor conditions prevent you from planting. Moisten your growing medium, plant your seeds and then cover your containers in clear plastic and store them in a cool, dark place, or start your seeds between two paper towels and transfer the seeds that emerge successfully to your growing medium.

Outdoors

• A common method for planting outdoors involves filling a 1-foot-deep trench with a balanced fertilizer and compost. Plant several seeds per hole, or place your seeds 1 to 2 inches deep, 2 inches apart. Protect your seedbed from animals or birds that may try to steal them, and keep it moist. After they sprout, thin the plants to 5 to 6 inches apart or as directed for the variety you select.

Scoring

• Several anecdotal tricks exist to trigger a better, faster germination of sweet pea seeds, including storing the seeds in the freezer just before planting, but there is only one tried and true method suggested by extension resources such as the Washington State University Extension: nick the seed coating. Whether you score your seeds with nail clippers, scratch them with sandpaper or rough them up with an emery board, you will both speed and increase germination results in your sweet peas.

Soaking

• Do not bother soaking your seeds overnight or for up to 24 hours before planting. There is no evidence supporting the theory that soaking the seeds will increase germination or speed the process, according to the Texas Cooperative Extension, which notes that the seed coat of the sweet pea is water insoluble.

Considerations

• Sweet peas require 10 to 21 days to germinate. The seeds don’t need light to trigger emergence, but the plants will need sun exposure as soon as they appear. Select a site that provides full sun and has good drainage to prevent issues with rot. Plant in a rich soil, or add amendments to improve the soil. Mulch your plants’ roots to keep them moist and cool. To prevent disease issues in young plants, the University of California Integrated Pest Management Program warns against planting sweet peas in locations where legume crops were previously grown.