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 up my trellis before planting my peas. Our trellis is 7 feet tall and these will continue growing 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, but you can do as little as 4 inches if you’re out of space.
Decide how you will go about watering your plants regularly.
Feed your plants every 2 weeks until they are looking lush and full and at least knee high, and then you can stop. Some good options for fertilizer would be easy homemade compost teas or fish emulsion. You can also side dress them (which just means to place on the soil near the roots) with fresh compost.
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 have to tie your SPs 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” or give them a haircut instead of letting them grow over the trellis. This will actually activate side shoots and produce more flowers.
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 poisonous.
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 set seed and 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 the garden has to offer.