If your yucca plant is overgrowing its boundaries, of if you want to share your yucca with gardening friends, it's easy to divide the yucca to create new plants. If you live in a climate with hot summers and mild winters, divide yucca during the fall so the roots have time to establish before the next summer's hot weather. If you live in a cold-weather climate, divide yucca in late spring.
Dig the yucca with a garden fork. Insert the garden fork straight down into the soil 6 to 8 inches from the yucca, and rock the fork back and forth to loosen the yucca's roots. Repeat in a circle around the yucca until you can lift the yucca from the soil.
Rinse the soil from the roots with a garden hose, then cut the yucca clump apart into divisions 3 inches or larger with a clean, sharp knife. Discard any tough, woody sections in the middle of the clump.
Put the remaining divisions in a shady area for a few day so the cut areas can seal. This will prevent rot on the cut edge, and will promote better rooting.
Dig a shallow hole in a sunny, well-drained spot for the newly divided yuccas. The hole should be the same depth as the yucca's roots, but no deeper.
Plant the yucca in the hole. Fill the hole with reserved soil, along with a handful of compost. Tamp the soil lightly to remove air bubbles and prevent settling.
Keep the soil moist until you notice the emergence of new growth, which indicates that roots have developed. After this time, water yucca only occasionally. Once a month is generally sufficient.