Gardeners have been growing lilies for a long time–paintings of this lovely flower have been found on ancient Minoan frescoes dating back to 1580 BC, and gardeners in Pompeii grew lilies with oleanders, pinks, and morning glories. In full bloom, dangling from tall thin stems, they almost look like small birds hovering above the garden, and are delightful.
But once the flowering is over, I always experience a moment of befuddlement. The withered flower leaves behind a stark structure of flower stems and the flower pistil, and it doesn’t look good. But since the lily is a bulb, we know we shouldn’t cut the plant back at all, right? Or can we cut off just the stark top structure that bore the flowers? Lily information in books glides over this. So I decided to seek out an authority on lilies, and contacted Mr. Larry Diehl, who is a Past President of the North American Lily Society. (Their website is at http://www.lilies.org and has links to regional lily societies, as well as more info on lily care.) Mr. Diehl very kindly sent me the following description of lily aftercare. Fortunately, it looks like we can snip off that top structure but we do need to leave the rest of the plant to wither. Here is what Mr. Diehl has to say:
Once lilies have flowered they devote their energy to two things. If a wandering pollinator (a human by design, or an insect by chance) has produced a successful fertilization they will devote some energy to producing seeds. For the average gardener who does or should not care about this,they should snap off any developing seed pods so that the plants total energy can be devoted to building up the bulb for next year’s season. No additional fertilization should be given at this time (after flowering). If the grower’s climate is humid or if there is wet weather the grower should be on the lookout for botrytis and at the first sign of brown spots should spay with their favorite fungicide. Susceptible plants can quickly turn brown and deprive the bulb of full nourishment required at this time.
As long as the stem and leaves are green they should be kept in place as they are feeding the bulb. Only after the plant has fully senesced (turned brown) should they be removed. A fully dried stem can be pulled away from the bulb by pulling and applying a slight twisting motion. However, the proper time for this is not easy to judge and it is quite likely that the inexperienced gardener may pull up the bulb roots and all. If this should occur continue to remove the stem and then replant the bulb at a depth about 3X the diameter of the bulb. Water immediately to compact the soil around the bulb.
For the inexperienced it may be better to simply cut off the stem at ground level. Let me add a couple of other thoughts at this point. The old stem left in the ground may be a barrier to the stem coming up next year. This can be especially true if the stems have been cut and the stub left in place over a few years. It is good practice to see if the old stub can be carefully removed in the spring before the new stem appears. (I mean carefully! For almost every lily the new stem has the flowers for the year in its tip and damaging the emerging stem can result in no flowers for the year. Or if the new stem is broken off the plant will produce nothing for the year and the bulb will be set back (but may still survive)).
Over time well grown lilies may form a clump and become crowded. If the plants seem less vigorous or produce less flowers per stem it is probably time to dig the clump and divide them. This should be done as soon as the plant has senesced. The bulbs may have split apart naturally or it will be easy to see where they can be split. Dust any bulb parts that are damaged in the splitting with a garden bulb dust and replant as soon as possible. True lilies are never dormant and have no protective tunic (like say tulips) so they should spend as little time out of the ground as possible. Replant bulbs 9-12 inches apart and water in.
Another thought. Many lilies produce stem bulblets that cluster around the stem and may be evident as bulbs themselves or by small leaves that surface the ground around the stem. These small bulbs can accumulate and also produce crowding. The fall cleanup time is the ideal time to relocate them away from the parent bulb. Plant them at a depth of 2-3X the size of the bulb. Lilies that produce bulblets allow you to build up impressive amounts of lilies in a pretty short time!