Lily bulbs may be planted in spring or in the fall, usually from mid-September through mid-October. If you find hardy lilies growing in containers, you may add them to your garden throughout the growing season. When buying locally, select firm, plump bulbs with roots attached. Plant them as soon as possible. Bulbs never go completely dormant so they must not dry out before planting. Plant mail order bulbs as soon as possible, also.
Asiatic and Oriental lilies grow best in full sunlight. In Minnesota, they need six to eight hours of direct sunlight in order to perform well. They’ll grow taller, more spindly, and floppier in reduced light. Martagon hybrids, a group of turk’s-cap lilies, are prized for their ability to bloom well in shadier conditions.
For best effect, plant lilies in groups of three or five identical bulbs. Space them eight to twelve inches apart, keeping groups three to five feet apart, depending on the vigor and size of the lilies. Plant small lily bulbs two to four inches deep and large bulbs four to six inches deep, measuring from the top of the bulb. Divide and replant large clusters of bulbs every three years or so – or when it seems they are not blooming as well as originally.
Never plant lilies where standing water collects after heavy rainfall. Well-drained soil is an absolute must. Add lots of organic matter to clay soil to create a raised area with improved drainage. Incorporate organic matter into light, sandy soil also, to help hold onto nutrients and prevent it from drying too rapidly.
Before winter, mulch over newly planted bulbs with four to six inches of loose, weed-free compost, leaves, or wood chips. This delays soil freezing and allows roots to continue growing longer. Mulch also insulates the soil against fluctuating temperatures, delaying the emergence of frost-tender shoots in spring.
Hardy established lily bulbs don’t need winter protection where good snow cover is dependable. Considering Minnesota’s weather history, however, it’s always safest to apply a winter mulch. Wait until some time in November when the ground begins to freeze, before spreading it.