Sweet peas must be kept nice and wet throughout the summer. Water them lightly every day it does not rain. Check the soil surrounding the sweet pea stems often to make sure it doesn't dry out. Sweet peas are quite prolific, and a monthly application of mild fertilizer will keep them blooming for many weeks. It's not mandatory, but it's helpful if you want to make the most of your flowers. Use compost, manure or a high-potassium commercial fertilizer application. Cutting the flowers promotes new growth, so don't hesitate to bring in some fresh blossoms or make a bouquet for a friend. Wait until the flowers have reached their fragrant and colorful peaks before cutting. You should also remove faded blossoms, which sap energy from the plant and prevent more flowers from growing. These annuals won't come back on their own next year, but you can enjoy them again if you save the seed pods and plant them again in the winter or spring, depending on where you live. This will encourage new growth in the form of more side-shoots and flowers. You can just use your fingernails to pinch off the shoots.
Water them often during the hot months. Fertilize once a month. Harvest the flowers regularly. Save the seed pods from your plants for next year's crop. Pinch off the shoots once your peas are 6 inches or longer.