Deadhead your lily when the plant is in bloom. Growing in soil does have some advantages for tree lilies. Canna grow as perennials in areas with mild winters. Thanks in advance, ... Hi Jennifer,I cut mine back each year and I don't know why but they come back bigger and more beautiful each time. Each year for the first 3 years that Althea has been planted, cut the shrub down by 1/3. The soil should not be soggy, but it should never be completely dry. Lilies: growing in containers. Water your tree lilies regularly throughout the growing season. Plant tree lily bulbs in autumn for blooms the following summer. An althea cut down to the ground will re-grow. Don't be tempted to cut back lily stems completely until they have yellowed in the autumn. It's always advisable to cut lily stems down to about 6 inches after they die. Cut off the flowers as they fade and let the stalks die back naturally as this lets the bulb build up for next years flowers. In mid-spring cut back last year's shoots to one or two pairs of buds from the base. Water the bulbs deeply after planting. If you’re growing lilies, you probably want to keep the foliage around through the summer so the plants will come back the following spring. The anthers can be removed as soon as flowers open. Tree Lily Bulbs/Orienpet Lilies Information. You should deadhead blooms and cut back stems as the lilies bloom during the growing season, and again let the foliage die back, but once it has died back in the fall, it can be cut off at this point. But when and what to prune depends on the type of plant and the climate you live in. As the bulbs multiply, it causes overcrowding in the growing area. Another reason to leave the foliage in place until spring is to mark... Diseases. Step 1. Leaving faded blooms on a lily flower discourages proper growth. After blooming, the foliage begins to yellow and fade. Make the cuts at the base of the flower stem, where they join the plant. If it doesn't, cut it to 1 to 2 inches long. Pruning shrubs Gardening Guides from BBC Gardening. Look for branches that cross one another, and cut the branch that will best open that area of the shrub.