Sweet peas need well-draining soil amended with plenty of compost and organic matter. Work compost and aged manure into a depth of at least 1 foot. Sweet peas prefer soil a bit on the alkaline side; amend with lime if soil is acidic.
In most areas, choose a location in full sun. If your summers are very hot such as in Arizona, choose a location that gets morning sun and some afternoon shade.
Plant seeds 1 inch deep, 2-3 inches apart. Thin to about 5 inches apart when seedlings are 2-3 inches tall.