My Mountain Laura is close to 100 years old; it is beautiful. But it blooms just on one side. I can't remember if it blooms on alternating sides, but the entire shrub does not bloom at one time. Is that common?: Also, is it advisable to deadhead the Mountain Laurel which is quite a job. It is in Massachusetts and is a beauty and I don't want to lose it. Thank you. I don't know how to upload; I can send photos via email if that will help.
Although a lot of the information says it will grow in part shade, it will definitely bloom better if it is in full sun. Obviously, with a plant this age, you're not going to be moving it into a sunnier spot, but perhaps there are shrubs or trees around it that could be trimmed back to provide more sunlight.
Second, don't fertilize it, especially not with nitrogen-high fertilizer, such as lawn fertilizers. The plant is a legume, and has an internal mechanism that permits it to fix nitrogen in the soil, some of which it uses itself, and some of which can be used by other plants. Many plants are adversely affected in terms of blooms when they are over-treated with nitrogen.
The mountain laurel produces flowers only on one-year-old wood. Pruning now, getting out weak branches, trimming off long, thin stems, and general cleanup should propel it into blooming on that new wood that will sprout after the trimming.