Bone meal is not producing expected growth from kelp

Dig straight down at least 15-20 blocks on either creative or survival, leaving a 1x1 column of air, making sure all sides are made up of solid blocks. Place a dirt block at the bottom of the hole, and water at the top, so that the water flows directly from the top of the hole to the bottom. Place kelp on the dirt block, and use bone meal to grow it until you cannot grow it any longer. This should allow you to keep growing the kelp until it reaches the top water source block, and is a commonly used system for creating bubble elevators. The issue is that the kelp will not grow all the way to the top. It will reach a seemingly random point, and then stop growing, even as you attempt to use more bone meal.