Apply a balanced, slow-release fertilizer blend, such as a 10-10-10 analysis, at half the rate recommended on the label for the yucca size. Make one annual application in early summer.
Spread the fertilizer on top of the soil around the yucca plant. Leave a 6-inch space between the fertilizer and the yucca base so fertilizer doesn't come in direct contact with the leaves.
Water the soil thoroughly after applying the fertilizer. The water helps the fertilizer dissolve into the soil, where it will reach the root zone of the yucca plant.
Fertilize yuccas beginning one year after planting and continue to fertilizer once a year until the yuccas are three to five years old. Mature, well-established plants typically don't require fertilization.