Yucca (Adam's needle)

About Yucca (Adam's needle)

Adam's needle is the tough garden yucca: an evergreen clump of stiff, sword-shaped leaves edged with curly white threads that sends up 5-6 ft stalks of nodding, creamy white bells in late spring and early summer (NC State, Clemson). It is native to the eastern U.S. from Long Island and Pennsylvania south to Florida and Louisiana, and soapweed yucca is native to the Great Plains from Montana and North Dakota south to Texas, New Mexico and Arizona (wildflower.org). Only the little yucca moth pollinates the flowers, and its caterpillars eat some of the seeds in return (NC State, wildflower.org). This is not the cane yucca sold as a houseplant.

Adam's needle is hardy in zones 4-10, and soapweed yucca, one of the most cold-hardy yuccas, in zones 4-8 (NC State). Native and not listed as invasive, though wildflower.org notes Adam's needle escapes from gardens in the northern part of its range.

When to plant

Timing is counted from your average last spring frost (and first fall frost). Sow & Tell works out the actual dates for your ZIP code.

Plant potted yuccas from spring through fall (Clemson) in sun and well-drained soil, 3-6 ft apart (NC State). Keep them away from walks and patios because the leaf tips are sharp. Make more by dividing offsets, by root cuttings or from fresh seed (NC State, wildflower.org).

Soil

Any well-drained soil, including clay, sand and shallow rocky ground; it can't take waterlogged soil, and wet spots bring leaf spots and blight (NC State, Clemson).

Test the soil first; yucca grows in clay, sand or rocky soil as long as it drains, with pH about 6-8 (NC State, Clemson).

Feeding

• Spring after new growth starts, only if a soil test shows a need: slow-release complete fertilizer in a 3:1:2 ratio, or what the soil test calls for. Spread it evenly over the root zone and water it in; a typical soil-test rate for shrubs is about 2 lb of 12-6-6 per 100 sq ft (Clemson). Follow a soil test.

Wet, poorly drained spots lead to leaf spots and blight (NC State, Clemson). Mature shrubs in decent soil often need no fertilizer, and too much pushes leaves over flowers (Clemson). NC State lists the yucca plant bug as its insect pest.

Harvest

Adam's needle blooms in late spring to early summer (April-June in the South); soapweed yucca blooms June to August (NC State, wildflower.org). Cut the flower stalk off at the base after bloom (Clemson), or leave it if you want the seed pods.

Varieties (6)

Clemson and NC State document 6 named cultivars; we found no others in extension sources.

Good neighbors

Baptisia (false indigo)

A design pairing, not pest control: NC State suggests a variegated Adam's needle with yellow-flowered baptisia 'Carolina Moonlight'.

Diseases and problems

Leaf spots, Leaf blight

In the kitchen

NC State lists Adam's needle flowers as edible, with a slightly bitter, artichoke-like taste, raw or cooked in soups and stews, and lists the flowers, buds and young pods of soapweed yucca as edible too. Use only unsprayed flowers you are sure of.

Safety: NC State rates soapweed yucca low in toxicity: its saponins are mostly in the roots, and it doesn't cause skin rashes. The stiff, needle-tipped leaves are the real hazard, so Clemson advises keeping yuccas away from walkways; wear gloves when working in the clump.

Pets: Toxic to dogs, cats and horses (ASPCA, Yucca species): its saponins can cause vomiting in dogs and cats, and liver disease and skin irritation in horses.