Double fuchsias have an extra frilled row of petals under the sepals. A fuchsia flower has flanking sepals that are usually white, and a corolla of colored petals under the sepals. Double-petaled fuchsias have excess petals or a double corolla. The flowers may be up to 3 inches long and start out as a tight capsule of closed white sepals. As the flower opens, you get a peek at the color inside, which is usually darker than the flower will be at maturity. The sepals open up to reveal the ruffled petals and dangling stamens with one really long pistil. All fuchsia flowers are attached to their stem or pedicel by a tube that houses the ovary.
Fuchsia plants are big feeders and need a steady supply of nutrients. This is hard to provide in pots and containers because most of the nutrients are gone in six weeks. Fertilizing is helpful, but the plant needs the proper pH in order to uptake nutrients. Fuchsia perform best in a pH of 6. A potting soil that has been inoculated with mycorrhizae, or beneficial fungi, will help the roots bring up nutrients. The fungi form a symbiotic relationship with plant roots that assists both species.
Plentiful water is necessary for fuchsias, and especially for potted plants because containers dry out quickly. Your soil mix should have generous amounts of compost, coir or vermiculite for water retention. Compost both holds moisture and helps with tilth, and therefore drainage. Vermiculite is useful for both as well, while coir is an organic matter that will retain moisture. Double fuchsias make excellent plants for hanging baskets, where the constant flow of air around the pot will dry it out if the soil mix doesn't contain some water-retaining composite.
You can use a standard potting mix to grow fuchsias, but be aware of the plant's food and water needs. A good homemade fertilizer is two parts loam, one part compost and one part peat. You can incorporate chicken manure or some other natural fertilizer at planting. A feeding program every two weeks with a diluted plant food or a granular time-release food is a great way to give the plant the nutrients it needs to continue blooming. Fuchsias start easily from cuttings, which should be rooted in a half peat and half sand mixture.