Tree lilies are not trees, nor are they woody perennials. Like other lilies, they are bulb plants -- but these are bred to grow very tall and strong. Although they won't grow to tree height, they can reach heights of about 8 feet. Tree lilies are "Orienpet" lilies (Lilium henryi --- Lilium speciosum "Rubrum"), a hybrid of the showy trumpet lily and the hardy Oriental lily. The result is a fragrant, tall, sturdy lily crowned by large, showy flowers. Like most lilies, they are relatively easy to grow.
Choose a location that is exposed to morning sunlight but is protected from hot afternoon sun. A well-draining location is a must, as standing water will cause the bulbs to rot. Oriental lily hybrids also prefer acidic soil, according to the University of Minnesota extension. Acidic soils have a pH level of 7.0 or below.
Amend the soil with phosphorus-heavy, slow-release fertiliser (5-10-10). This will encourage the lily bulbs to develop strong roots. Work the fertiliser into the soil with a shovel or till. Follow the instructions on the package, which will specify amounts for your planting site and the number of lily bulbs you are planting.
Plant the bulbs in a hole that is at a depth equal to three times the diameter of the bulb. Use a bulb planter, shovel or trowel to dig the holes. Plant individual bulbs at least 4 inches apart. Fall planting will yield midsummer blooms.
Cover the entire planting site with 4 to 6 inches of straw mulch.
Keep the soil slightly moist, but not soggy or waterlogged. Do this once the bulbs have sprouted above ground. Water when the top layer of soil feels dry to the touch, and water at the soil level to avoid wetting the foliage or blooms. Many fungal diseases, such as botrytis blight, spread on water and can develop when water is left to sit on plant leaves.
Use string to tie the plant to a stake, trellis or other support structure once it gets too tall to support the weight of its flowers.
Cut off the spent flowers with pruning shears, but leave the foliage until it fades. This usually happens after the first hard frost. Once that happens, cut the tree lily back to the ground.
Tree lilies are hardy in USDA Plant Hardiness Zones 3 through 7, according to the "Fine Gardening" magazine website.
Rabbits and deer love to nibble on these plants. Rabbits will even dig up the bulbs. For these reasons, consider planting them in a protected area if you have a population of these animals.