Your Show-Me Garden: MU Extension brings you gardening tips from experts around the state.

MARBLE HILL, Mo. – Most people don’t think about planting flowers until May, but don't wait until then if you want to grow sweet peas, notes a University of Missouri Extension horticulturist.

“It is best to plant seeds outdoors as soon as the ground is workable in very early spring,” said Donna Aufdenberg.

Sweet peas are cool-season plants that can reach 4-6 feet and bloom from May to June, Aufdenberg said. Most sweet peas are annual flowers. There are a few perennial varieties, but they lack the fragrance of the annual varieties. They can be planted in full sun to partial shade (afternoon shade is preferable). They need moist, well-drained soil with a neutral pH of 7.0-7.5. If you have heavy, clay soil, you will need to amend it with organic matter for sweet peas to grow well.

Sweet peas are easy to start indoors, she said. Scarify (nick or scratch the seed coating) and sow several seeds in individual pots and keep in a warm location (60-75 degrees). Use a good-quality potting soil and keep the soil moist but not drenched. Once the seedlings sprout, give them as much light as possible to avoid leggy growth. Thin to one plant per pot after true leaves form. Keep seedlings cool and do not coddle or overfertilize. Harden the transplants before moving them outdoors.

Pinch the growing tip on young plants to encourage branching. “For vine-type sweet peas, provide support such as a trellis at the time of transplanting,” Aufdenberg said.

Place plants in a location with good air circulation. Water in the morning time to avoid powdery mildew. Mulch plants well after planting to keep the roots cool. Water regularly to keep plants thriving and blooming.

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