Spineless yucca

Identification and origin

Yucca gigantea belongs to the family Asparagaceae. It is still very often sold under its old names, Yucca elephantipes and Yucca guatemalensis. Its native range runs from central Mexico through Central America (Guatemala, Belize, Honduras, Nicaragua, Costa Rica and Panama), in tropical habitats with a marked dry season. It has naturalized in Ecuador, El Salvador, parts of the Caribbean and southern Europe (Spain, Portugal and Italy).

It is the tallest of the yuccas. It usually forms several trunks whose bark thickens and roughens with age; elephantipes means “elephant-footed.” The leaves, arranged in spiral rosettes at the tops of the trunks, are leathery, smooth, sword-shaped and pale to blue-green, ending in a soft tip without the sharp spine of most yuccas; they are usually 12–18 in long and up to 4 ft on mature plants. As it ages, the plant sheds its lower leaves, exposing the trunk. In the ground it reaches 15–30 ft tall; in a pot it stays far more compact, and the size of the container limits the size of the plant. It grows quickly. Large plants send up tall stalks of creamy white, bell-shaped flowers in the warm season, but almost never indoors.

Light

It loves full sun, at least six hours a day, and tolerates partial shade. Indoors, keep it in a south-facing window in winter; in summer, an east- or west-facing window, or a sheer curtain against direct midday sun, keeps it from overheating. Ventilate the room well in hot weather. Turn the pot regularly: the plant leans toward the light and quickly gets lopsided. In too little light, the leaves sag and droop.

Watering

It handles drought well and fears overwatering most. During the growing season, from spring through late summer, water generously but let the mix dry out between waterings. In winter, when the plant is not growing, wait until the top 2 in of the mix is dry, then water thoroughly and let the surplus drain away; in a cool room, give only enough to keep the foliage from deteriorating. Lower leaves that suddenly turn yellow and limp point to overwatering; crisp, brown lower leaves point to underwatering. The gradual loss of a few lower leaves is normal.

Potting mix

Excellent drainage is essential. For a potted plant, mix one part potting soil with three parts perlite or sand, or add 20 to 30 percent grit to a loam-based potting mix. It tolerates acid, neutral or alkaline soil. Use a pot with drainage holes that is stable and heavy enough not to tip under the weight of the trunks. While it is growing, a balanced liquid fertilizer every two weeks is plenty; do not feed in winter.

Temperature

It likes warmth, 70–90 °F in the warm season. Do not let it drop below 50 °F: that is the recommended minimum for a houseplant and the point at which to bring in a plant that has summered outdoors. During its winter rest, kept nearly dry, it tolerates nights of 45 °F with slightly warmer days, which makes it a good plant for a cool sunroom. It can go outside from late spring to late summer in a spot sheltered from wind. Outdoors year-round, it is grown in USDA zones 10a to 12b.

Repotting

Repot in spring, when growth resumes, into a pot only slightly larger: a large volume of soil stays wet, and the size of the container partly determines the size of the plant. If the roots have started to rot, unpot the plant, remove the excess mix and damaged roots, and replant in a pot just big enough for the reduced root ball, using a little fresh mix; keep it warm and water very sparingly until it recovers.

Pruning

Pruning is not normally needed: in spring, remove damaged leaves and spent flower stalks. If the yucca gets too tall, you can cut a trunk back by half in spring as growth resumes; there is a slight risk, but a healthy plant responds well. The top you cut off can be used for propagation.

Propagation

In spring, take stem cuttings 8–10 in long, measured from the tip, and set them in a coarse, sandy rooting mix in partial shade, in a propagator with bottom heat of at least 64 °F. Offsets that sometimes appear at the base root easily: in early spring, expose them, cut them off where they join the parent, let them dry for a couple of days, then treat them like cuttings, or cover them with plastic in a warm, bright spot out of direct sun. Sow seed in spring at 66–75 °F, after soaking it for twenty-four hours.

Common problems

The same symptom can have several causes: check watering, light and temperature before treating anything.

• Root rot: in a mix that is kept too wet.
• Lower leaves suddenly yellow and limp: too much water. Cut back and let the mix dry out almost completely.
• Crisp, brown lower leaves: too little water, or simply the natural turnover of foliage.
• Sagging leaves: too little light, but also check for over- or underwatering.
• Pests: mealybugs, scale and aphids, especially on flower stalks; outdoors, black weevils and yucca moth borers can tunnel into roots and stems, and snails chew the leaves.
• Leaf spot: brown fungal spots sometimes appear, especially in wet weather; they usually do little harm.

Toxicity

Toxic to dogs, cats and horses. Saponins, concentrated mainly in the leaves and roots, cause vomiting in dogs and cats, and liver disease and skin inflammation in horses. In people, eating the plant can cause nausea, vomiting, diarrhea, headaches and dizziness; the sap can also cause minor skin rashes, so wear gloves when handling and pruning it. Keep it out of reach of pets and children and, if it has been eaten, call a veterinarian or poison control.