Sweet peas are a cool-season flower, so plant them early in the growing season. In Southern California, I start my sweet peas October through December.
Choose a sunny spot to plant!
Plant in fertile soil with ample compost or manure (horse, chicken, or rabbit) gently worked into the top few inches of the soil before. Sweet peas are heavy feeders.
Provide a trellis of some sort preferably on the North side of your plants, for the plants to climb. I put my trellis up BEFORE planting my peas. Our trellis is 7-feet tall, and my plants will grow even taller than 7-feet if I let them! Keep in mind that you must be able to reach the top of your trellis to harvest the flowers, and it isn’t that fun to stand on a ladder and harvest sweet peas.
Space plants 8-inches apart directly next to the trellis. A tighter spacing than 8 inches isn’t ideal as it will decrease airflow and promote fungal diseases such as powdery mildew.
Decide how you will go about watering your plants regularly.
Autumn-sown sweet peas will naturally branch so you do not need to pinch them. If for some reason a plant fails to branch, then pinch (or snip) out the growing tip above a set of leaves.
You must tie your sweet peas up the trellis as they grow, or they’ll topple. Compostable twine or garden Velcro (that can be reused yearly) works great! Stay up on this weekly, or you’ll have a real mess on your hands that can’t be remedied.
Once your sweet peas reach the top of your tall trellis, I suggest you “top-them,” instead of letting them grow over the top of the trellis. This will actually activate side shoots and produce more flowers in the long-run.
All parts of the sweet pea plant can be poisonous, so use care around children and pets. I give my kids a rundown several times a growing season about which plants currently in the gardens are toxic for added safety.
Once your sweet peas begin blooming you must harvest all of your blooms at least twice a week so the plant will continue blooming. If you do not, and instead let the flowers remain on the plant, it will trigger the plant to begin producing seed and eventually stop flowering.
Visit your sweet peas daily. Watch for aphids and mildew. Inhale deeply and appreciate the sweetest fragrance, and some of the most beautiful flowers, a cut-flower garden has to offer.