Adam’s needle (Yucca filamentosa) is a compact evergreen shrub highly appreciated by horticulturalists and landscapers worldwide. Yucca filamentosa takes the spotlight in almost every garden due to its stunning looks. It is easily recognized by its large clusters of gentle white flowers, which are in sharp contrast to the green rosettes of sword-shaped leaves.
I. Appearance and Characteristics
Yucca filamentosa, Adam’s needle and thread, is a species of flowering plant in the family Asparagaceae native to the southeastern United States. It is an evergreen shrub valued in horticulture.
This plant is most commonly found in sandy soils, especially in beach scrub and dunes, but also in fields, barrens, and rocky slopes, though it grows well also in silt or clay soils.
Usually trunkless, it is multisuckering with heads of 75 centimetres (30 inches) long, filamentous, blue-green, strappy leaves. Y. filamentosa is readily distinguished from other yucca species by white, thready filaments along the leaf margins. Flower stems up to 3 metres (10 feet) tall bear masses of pendulous cream flowers in early summer.
Y. filamentosa is widely cultivated in mild temperate and subtropical climates. A fairly compact species, it nevertheless presents a striking appearance with its sword-like leaves and dramatic flowerheads. It is naturally a focal point in the landscape, also providing a tropical touch in temperate gardens. It needs full sun and a well-drained soil, preferring an acid or slightly alkaline pH range of 5.5 to 7.5. It develops a large, fleshy, white taproot with deep lateral roots. Once planted and established, it is difficult to remove, as the roots keep sending up new shoots for many years. It is normally hardy down to −29 °C (−20 °F), or U.S. Department of Agriculture (USDA) hardiness zones of 5 to 9: UK H7).
II. How to Grow and Care
Sunlight
Adam’s Needle likes a sunny and warm environment as it grows – the plant will find it difficult to bloom in an environment with insufficient sunlight. However, Adam’s needle does not like strong sunlight. It has a certain level of shade resistance, making mild, filtered sunlight your best option. Shade should always be provided in areas receiving direct sunlight.
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 4a-10a, 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.
Watering
Adam’s needle has good drought tolerance once established and 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 if there is not sufficient rainfall.
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.
Fertilizing
The adam’s needle does not require a wide spectrum of nutrients during its growth period. However, a fertilizer can encourage better growth. It should be noted that a basal fertilizer should be applied when planting or transplanting.
A compound fertilizer should be applied once in the spring and fall, and no fertilizer should be applied in the winter. This will prevent vigorous growth in the winter, which is unfavorable for overwintering. You could also apply a compound fertilizer during the plant’s rapid growth period, so as to accelerate blooming.
Planting Instructions
The adam’s needle is easy to plant, with or without soil, and the best time to do so is in the spring or fall. Well-drained sandy soil should be selected, and you will need to prevent water from accumulating around the plant during a rainy spell.
For planting, sufficient basal fertilizer should be applied to the bottom of the flowerpot or pit (a compound fertilizer is usually selected as a basal fertilizer). After planting, if your adam’s needle has a rope binding its leaves, untie this, allowing the leaves to fully extend. Water thoroughly. A compound fertilizer should be applied once in the spring and fall – don’t use a fertilizer in the winter.
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, you can wait until their seed pods are ready to harvest. In the 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 them down close to the base of the plant.
Propagation
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:
- You’ll need a spade or shovel, a sharp, sterilized knife, a pot with many holes, and a well-draining potting mix. Also, wear sturdy protective gloves and long sleeves.
- Using the spade or shovel, dig up part of the root. With your knife, cut off a 3-inch section of healthy root.
- Transplant the section of root into a well-draining potting mix.
- Keep it in a warm, well-lit indoor room.
- In 3 to 4 weeks, the plant should produce roots, and you should notice new growth.
To propagate from a stem cutting:
- You’ll need a sharp knife or garden pruners to remove one or several stems between 5” to 10” inches long. You’ll also need well-draining potting soil and a pot with drainage holes.
- Allow the cut to dry for 24 to 48 hours before you plant the stem in well-draining sandy soil with the cut end down.
- Plant it in a shady location and keep the soil moist until roots begin to develop. Root growth can take one to two months. After two months, you can gently tug at the leaf and will feel if roots have taken hold, or you may notice new growth from the stem.
Offsets or pups grow at the base of the parent plant and are genetic clones of the mother plant. To propagate from its offshoots:
- You’ll need a new pot with well-draining soil and, optionally, a sharp knife.
- If your yucca is in a pot, remove the plant, and identify the offshoot or pup. Or, if in the ground, carefully dig around the offshoot. Most offsets will have a root system. You should be able to break it away from the parent plant easily. If offset roots are connected to the mother, gently cut them away from the parent.
- Pot the offset with its roots in its new pot. Provide water. Keep the soil moist for the first few months until you notice new growth.
- Allow the offset to root in the pot before transplanting the new root ball into the garden.
Potting and Repotting
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 root bound. 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 the 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.
Pests and Diseases
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.
Common Problems
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.
III. Uses and Benefits
- Ornamental uses
Yucca Filamentosa, commonly known as Adam’s Needle is a small clump-forming evergreen shrub with long sword-like, almost erect leaves of deep green, with small cream color filaments. In the months of July and August the Yucca Filamentosa produces these stiff upright stems with spikes of wonderful white, bell shaped flowers.
Although mediterranean looking this Yucca is suitable for planting almost anywhere, often in flower beds and borders or coastal gardens making a perfect architectural plant with the added height when flowering.
- Culinary uses
Once the seeds have been removed, the fruits can be cooked and eaten. The large flower petals can also be eaten in salads.
- Other uses
The leaves, stems and roots of this plant can be used to stun fish. The Cherokee used it for this purpose.
IV. Harvesting and Storage
The adam’s needle usually blooms at night, between summer and fall, and has a long blooming time. The flowers of most plants are large, spectacular and fragrant, making them popular for flower arranging. Its leaves contain tough fibers that can be used to make ropes.
