Mature plants about four or five years old will send up large flower stalks from the center of the foliage in late spring or summer. These stalks can be as tall as 8 feet, and are topped with numerous bell-shaped, creamy white flowers that attract butterflies and hummingbirds. Adam’s needle can be planted almost any time, though it is most commonly available at nurseries in the spring. Humans can eat the fruits and flowers of this plant; however, it is toxic to cats, dogs, and horses. Though this is a slow-growing plant, it’s best to give it 2 to 3 feet of open space, which will make it easier to work around the sharp, spiky leaves. Create a planting hole about twice as deep and wide as the nursery container, and plant the specimen at the same level as it grows in the container. Take care not to plant the yucca deeper than it sat in its nursery container, as this can lead to rot. You can also grow Adam’s needle in a large container. Yucca filamentosa has few severe diseases or pest issues. Adam’s needle attracts yucca moths at night, which are the main pollinator for this plant.
Light
This plant grows best in full sun but will tolerate a little shade. In low light conditions, however, yucca will stretch toward the sun.
Soil
Adam’s needle needs well-drained soil, and you should keep it a bit on the dry side. It does not require fertile soil, so it is a good choice for poor, rocky, or sandy soil areas. It also does not seem to mind pollutants or salty soil, making it suitable for roadside plantings. Yucca is a great choice when growing a rock garden, and it works well on a slope to provide valuable soil erosion control.
Water
Adam’s needle has good drought tolerance once established. It is often used in xeriscape landscaping. In its first year, water it lightly every week—depending on the size of the plant, light watering can mean a few ounces to a cup—but after its first growing season, it should not need supplemental watering at all. Container-grown plants will continue to need a small amount of weekly water, however, if there is not sufficient rainfall.
Temperature and Humidity
Although native to the southeastern U.S., this hardy succulent has naturalized farther north. You can plant Yucca filamentosa in USDA hardiness zones 5 to 10, as it readily adapts to all climate variations within those zones. This plant can handle temperatures down to 5 degrees Fahrenheit but may also survive temps of -10 to -20 degrees Fahrenheit if covered with mulch over winter. Adam’s needle grows best with moderate humidity but can acclimate to low humidity conditions.
Fertilizer
Adam’s needle usually does fine without any feeding, but if the plant is languishing, feed it once in spring with a granular, balanced, general-purpose fertilizer mixed into the soil around the base of the plant. For the amount to use, follow the product label instructions. You can give it an additional feeding after about three months if required, but don’t feed this plant too much, as it does best in somewhat poor soil.
Types of Adam’s Needle
‘Bright Edge’: Bicolored type of Adam’s needle; well suited for zones 4 to 9 ‘Golden Sword’: Bright variation with gold in its leaves ‘Garland’s Gold’: Golden and bright variety Yucca flaccida: Looks similar to Adam’s needle but leaves appear limp; grows in zones 4 to 10 Yucca glauca (Soapweed or Spanish bayonet): Grows about half the size of Adam’s needle; easily confused with soap-tree yucca; suitable for zones 3 to 10
Pruning
Wear long, sturdy gloves when working with this plant. It has sharp, spiky ends; a prick from this plant can cut you and some people experience a skin reaction when exposed to its sap. Overall, little pruning is required. Trim flower stalks down once the blooms have faded. Or, after the flowers fade, you can wait until their seeds pods are ready to harvest. In fall, remove yellowing leaves after they have dried. If you notice branching from the trunks, remove it in late winter or spring. Use sharp garden shears to prune away leaves by cutting down close to the base of the plant.
Propagating Adam’s Needle
Adam’s needle can be propagated by several methods: seed, stem cutting, rhizomes, or basal offshoots. It is best propagated in spring or summer unless you plan to propagate by division, then winter is best. Pruning yucca is sometimes necessary to keep a plant from growing too tall and unruly; pruned healthy stems are perfect for stem cutting propagation. Rhizomes are the underground root system of the yucca plant. Here’s how to propagate by rhizome division: To propagate from a stem cutting: Offsets or pups grow at the base of the parent plant and are genetic clones of the mother plant. To propagate from its offshoots:
How to Grow Adam’s Needle From Seed
Sow more seeds than the number of plants you ultimately want since germination is unpredictable. Start the germination process indoors in March. It can take four to five weeks for seeds to germinate. For best results, many gardeners soak the seeds overnight before planting.
Potting and Repotting Adam’s Needle
Adam’s needle does not need a large container; it can grow suitably in an 18-inch pot with ample drainage holes. It prefers to be slightly rootbound. Roots growing out of the drainage holes are signs your yucca is ready for a new home. You shouldn’t need to transplant it often—only every three to four years into the next size pot. Ideally, transplant your yucca during the winter months. To repot, use a porous succulent or cactus potting mix. Adam’s needle generally prefers to be alone in its pot, but it blends well with other large potted plants arranged on a patio or deck or around a sunny entrance. Adam’s needle needs a pot that’s only slightly larger than its rootball.
Overwintering
Yucca plants will stop storing water in their leaves during dormancy over the winter, protecting the plant from deep freezes. Winter burn may affect some of the leaves in regions with cold, windy winters. By late summer, start to reduce the amount of supplemental water the plant receives, if any. Stop watering entirely by September. Let the stalks naturally die back before cutting them. This allows the plant to store needed nutrients in the roots for next season’s growth. Adam’s needle can withstand 5 degrees Fahrenheit but will benefit from some winter protection. Insulate and protect it from the cold winter weather by cutting the stalks to the ground and applying a 6- to 8-inch layer of mulching material over the plant in late fall before the first frost. Cover the mulch pile with plastic sheeting or burlap to provide further insulation in the coldest areas. Hold the sheeting down with stakes or large rocks placed around the edges. Remove the sheeting and the mulch in the spring after the chance of frost has passed.
Common Pests
Yucca plants can fall victim to insect activity much like other plants, but their woes are generally easier to handle. You can dispatch pests like aphids and mealybugs with blasts of water from your hose. Scale bugs will fall away with neem oil. Agave plant bugs and mites will disappear after several applications of insecticidal soap. The only genuinely problematic pest that can kill your plant is an infestation of yucca weevils. Yucca weevils burrow underground and feast on the rhizomatous root. If you notice tell-tale holes in the leaves, pull up the root to inspect it. If weevils ravage the root, you may need to destroy it. But, if you can find a healthy, untouched portion of the rhizome, you can cut it off and repot it in a separate container.
How to Get Adam’s Needle to Bloom
Yucca plants may bloom from June up to September. However, if grown from seed it may not bloom until it fully matures, which can take four to five years. The flower stalks can grow up to 5 or 8 feet high, developing creamy-white bell-shaped flowers. Regular fertilization and trimming of the old flower head and stalk from the previous growing season will keep the plant healthy and encourage more growth and flowers in the following season. Adding phosphorus-rich fertilizer or bone meal to the soil can also encourage flowering. Also, if your plant is not flowering, it may need to be hand-pollinated. Yucca’s sweetly-scented flowers bloom at night, attracting the plants’ only pollinator, the yucca moth. If these moths are not present, you might need to provide a helping hand.
Common Problems With Adam’s Needle
Yucca is an easy plant to grow and maintain. Its pest problems are minor, and it’s cold-hardy and drought tolerant.
Leaves Turning Yellow
If you notice that the plant’s leaves turn yellow, you may be overwatering your plant. Other signs of overwatering include a spongy or soft trunk or a sour odor to the soil or the plant’s roots. Pull up a bit of the plant, and examine the roots. If they look black and mushy, root rot is present. If caught early, you can reverse root rot if you cut away the damaged part of the root and apply a fungicide. Also, reduce the water significantly. Yucca should only be watered when the soil dries out. A few yellowing leaves at the plant’s base are normal at the end of the growing season, however. Allow those leaves to dry out and then remove them.
Leaves Turning Deeply Green
If a yucca plant develops dark green leaves, this sign is usually a welcome sight. However, in an indoor yucca plant, or a yucca in too much shade, it can mean that your Adam’s needle is starving for more light. If your yucca plant’s leaves start to turn unusually deep green, the plant is trying to compensate for the lack of natural light by producing more chlorophyll to keep it alive. If the plant does not get more light shortly after that period, you may notice its leaves turning yellow and falling off.
Browning Leaf Tips
Browning leaf edges and tips combined with slow growth, leaf drop, and wilting leaves could signify that your plant is getting too much fertilizer. These symptoms describe fertilizer burn. Adam’s needle doesn’t need fertilizer, but if you provide it, only give it once at the start of the growing season, and maybe again three months later. If you think you might have over-fertilized your plant, the best action is to flush the fertilizer salts out of the soil with water.
