Lilies –true lilies of the genus Lilium, not daylilies of genus Hemerocallis–grow from unique bulbs that are composed of many individual lobes or scales which are joined together at their base like a head of garlic, which is a relative. They grow best in light, loamy, moist but well-drained soil with lots of organic matter in a spot that gets full sun or partial shade. How to fertilize lilies? There are two ways.
Fertilize When Planting
As noted above, lilies need soil that is rich in organic matter such as compost or manure. When you are preparing the flower bed in which you’re going to plant your lilies, work some aged manure or compost into the soil. This will provide a good nutrient-rich start for your new lily bulbs. Then as you make the hole for each individual bulb, add in a handful of bonemeal for even more nutrients. If you don’t have a ground-cover plant in the flower bed and it’s just bare soil around your new bulbs, add mulch over the soil to keep in moisture. Use grass clippings, chopped leaves, or straw as mulch, and they will eventually decompose and even further enrich the soil.
Fertilize After Blooming
In late summer or fall after the lilies are done blooming, add more bonemeal to the soil and rake it in around the plants. Then, mulch the flower bed with straw, grass clippings, chopped leaves, or evergreen branches. That will give the bulbs more nourishment and a nice warm blanket as they go dormant for the coming winter. Plus, the mulch will compost itself in place and become even more fertilizer next spring.