Answer: As you've discovered, sweet peas are not very heat tolerant. To enjoy the beauty and fragrance of sweet peas, plant the seeds in late February or early March. The plants will grow and bloom before the summer wether gets too hot. You can sow a second crop in late August and enjoy flowers throughout the fall. Straw mulch will help keep the roots cool and stretch the bloom season.<br><br>Sweet peas like ordinary garden soil and at least one inch of water per week - more when the weather begins to warm. An added benefit of growing sweet peas (or any member of the Leguminosae family) is that the roots can help fix nitrogen in the soil. Little nitrogen-rich nodes grow on the roots. If you cut the old plants off at soil level and leave the roots, the nodes will decompose and release nitrogen into the soil.
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