Yucca plants have tall blooming spikes and broad, sword-like leaves. Although native to desert climates, their hardiness and size have made them popular landscaping plants in other regions. If your yucca plants have grown too large for their space, you can cut them back while still maintaining their beauty.
Yuccas are drought-resistant and easy to take care of. Yucca plants grow by sending out rhizomes from the main stalk. The rhizomes sprout new baby plants, which is why yucca spreads so efficiently that some people consider it a pest. One way of propagating yuccas is to cut the rhizomes with baby plants from the main root. Dividing yuccas to control their growth works on the same principle. As the yucca plant grows, it's necessary to thin it out by dividing it because the plant can begin to crowd itself with too many clumps packed closely together.
You might be able to divide the yucca plant without digging it up. If you look around the base of the plant, you will see the smaller clumps of baby plants on smaller rhizomes, called offsets. Rhizomes look more like twisted underground branches than roots, and you don't have to be as gentle with them as you do with exposed root systems. Use a saw, shovel or a strong knife, such as a machete, to break the offsets of the main rhizome. Don't be afraid to use force---rhizomes can be quite difficult to break apart, and it's unlikely you'll hurt the main plant.
Propagating Yucca From Divisions
Divide yuccas for propagation in late fall or early winter, when the plant is dormant. If you want to propagate your yucca plant with the divisions, be a little more careful when separating the offsets from the main plant. To better see where the offsets are attached, you should dig up the whole yucca plant. You will still need to use a shovel, saw or strong knife to detach the offshoots from the main stem, but take care to preserve as much of the offset rhizome as possible.
If your yucca plant has grown so large that it needs to be divided, you probably have several viable baby plants there. This means that even if you damage a few offsets, you will have plenty more that can be planted. Before planting the offsets, put them in a cool place to dry off for a few days. Plant them in sandy, well-drained soil. Bury the rhizome up to the base of the foliage, and water it in well. Keep the plant well-watered for at least three months until it's established.