Yellow Asiatic lilies may look exotic, but like all Asiatic lilies they are tough, durable perennials that will require very little maintenance once they're established in the garden. Eventually, Asiatic lilies will multiply, creating a show-stopping clump of bright yellow blooms that will appear summer after summer. Plant Asiatic lilies in a sunny spot in early spring or autumn.
Plant yellow Asiatic lilies where they will be exposed to at least six to eight hours of sunlight every day. Although Asiatic lilies will grow in partial shade, without adequate sunlight, the stems will be tall and spindly.
Cultivate the soil to a depth of 12 inches, using a spade or garden tiller. Spread 4 to 6 inches of compost or manure on the soil, and work it in thoroughly. Asiatic lilies require well-drained soil so, if necessary, add an additional 4 to 6 inches of peat moss, compost or manure to improve drainage.
Dig a hole for each lily bulb. Plant each bulb and cover it with 4 to 6 inches of soil. Lilies will be most attractive planted in odd-numbered groups of three, five or seven. After planting, spread 2 to 3 inches or organic mulch over the area to keep the roots cool.
Water the Asiatic lily bulbs immediately after planting. After that time, keep the soil moist but don't water excessively. Water the Asiatic lilies in the morning so excess moisture will have time to evaporate before evening. Water at the base of the plant and avoid wetting the foliage as much as possible.
Begin fertilizing the Asiatic lilies when the shoots emerge from the ground, using a granular fertilizer for blooming plants. Fertilize the lilies every month during the growing season.
Mulch the Asiatic lilies in autumn if you live in a cold climate, especially if the ground won't be protected by snow. Spread 6 to 8 inches of an organic mulch such as pine needles, straw, shredded mulch or dry leaves around the lilies. Leave the mulch in place until after the last freeze in spring. At that time, spread a fresh layer of mulch around the plants to keep the roots cool.
Divide Asiatic lilies every three to four years, or whenever decreased blooming indicates that the lilies are getting crowded. Dig the clump of lilies with a garden fork. Divide the bulbs with your hands and plant the divided bulbs in a sunny spot or give them away. Discard old, woody or nonproductive parts.