It is generally recommended to cut the grass before fertilizing, as this can help the fertilizer to reach the soil more effectively. When grass is long, the fertilizer can get caught in the blades and may not reach the soil where it is needed. Cutting the grass to a shorter length can also help to stimulate growth and allow for more even distribution of the fertilizer. Additionally, when grass is cut, the clippings can be left on the lawn to decompose and provide natural nutrients to the soil, which can complement the effects of the fertilizer. Overall, while there is no hard and fast rule, it is generally a good idea to cut the grass before fertilizing to ensure the best possible results.