Double petal daylilies occur when the reproductive parts of the flower appear as an extra set of petals. The second set grows as a tuft in the middle of the flower or as a full flower set. These flowers grow as perennials in USDA zones 3 to 10, almost throughout the entire United States. Knowledge of how to grow these plants will help you produce an attractive addition to your garden.
Plant double petal daylily seeds about 1/8-inch deep in a seed flat filled with a mix of half peat and half perlite. Keep the seeds moist and place in a partially shaded area until the seeds germinate. This should occur in about two weeks.
Find an appropriate area to plant your daylily plants with full sun and well-drained, fertile soil. If the soil fertility is low, mix in 1 to 2 inches of organic compost about 6 inches deep.
Plant the double petal daylilies 18 to 24 inches apart to prevent crowding. Place them so that the point where the roots meet the foliage lies about an inch deep.
Water deeply after planting. Place a 2-inch layer of mulch around the base of the plants to keep down weeds and to provide even moisture for the double petal daylilies.
Water once a week to a depth of 10 to 12 inches when it does not rain. This will promote deep root growth and keep the tree moist.