Shepherd's needles' flowers are rather pretty, plentiful and very attractive to many species of butterflies. Click to download a large version (800x600) of this image.
Shepherd's needles or "butterfly needles" is a weedy annual or short-lived perennial herb with erect and ridged 1-4 ft (0.3-1.2 m) tall stems emerging from a strong taproot. The seedlings initially put out simple, long-stalked, opposite leaves with depressed midveins. As the plants get older, they produce upper foliage with compound leaves composed of 3-9 saw toothed oval leaflets. The leaves are 1-5 in (2.5-12.7 cm) long and up to 2.5 in (6.4 cm) wide, bright green on top and hairy on the underside. As the season progresses, the major branches tend to sprawl and root at the lower nodes where they touch the ground. The 1 in (2.5 cm) flowers, which grow in stalked clusters, look like coarse daisies with five white rays and pale yellow centers. The 0.25-0.5 in (0.6-1.3 cm) long ribbed seeds resemble flat black needles with 2-6 barbed hooks at each end. They are borne in loose round clusters that look sort of like fireworks exploding. In the tropics, shepherd's needles stays green year round, but grows and flowers most actively when the weather is hot and rainfall is plentiful. Shepherd's needles is sometimes called "Spanish needles", but that common name is usually used for Bidens bipinnata, which is a taller, darker green plant with more finely divided foliage and flowers that have no rays at all.
The shepherd's needles reach from a center point and can leap en masse up to 3 ft (0.9 m) in order grab onto your socks - that's a lie - but it sure seems true sometimes. Click to download a large version (800x600) of this image.
Shepherd's needles comes from tropical America, but it spread to Asia and the Pacific many years ago and is now widely naturalized throughout the tropics and subtropics everywhere in the world. Shepherd's needles thrives in gardens, farm fields, and disturbed sites.
Shepherd's needles does best in rich loose soil with lots of organic mater, but grows well on sand and limerock too.
Light:This species likes full sun. Moisture: Shepherd's needles prefers moist sites, but does well without irrigation through all but the most extreme droughts. Hardiness: USDA Zones 7 - 10. Plants are killed to the ground by heavy frost, but come back quickly from roots and/or seeds when the weather turns warm. Propagation: Shepherd's needles is a fast spreading weed. A single plant is capable of producing 3,000-6,000 seeds, which maintain viability for at least 3-5 years and germinate readily. They may be spread by wind or water, but are most often dispersed by people or animals who get the little seeds caught in their clothing or fur. It is seldom necessary to intentionally propagate shepherd's needles. Seedlings are usually abundant wherever plants have grown. Cuttings from mature stems would probably root easily, but why bother? Plants are easy to transplant.
A total weed, these roadside clumps of shepherd's needles grow back green and invigorated by the monthly mowings.
Shepherd's needles is sometimes planted in butterfly gardens or wildflower meadows, but is usually regarded as a weed. In South Africa, Zulus and Indians eat the fresh or dried leaves. They are boiled in a little water and eaten alone or with cornmeal when more palatable and nutritious foods are scarce.
Shepherd's needles will thrive, flower, and reseed profusely whether you want it to or not -- but nothing attracts more butterflies! The blossoms are a favored nectar source for many species including the great purple hairstreak (Atlides halesus), the dogface (Zerene cesonia) the red-banded hairstreak (Calycopis cecrops), the lantana scrub hairstreak (Strymon bazochii), and the gray hairstreak (Strymon melinus), and many others. Give shepherd's needles some space off along the far side of the yard where you can see the butterflies without getting the needles in your clothes and you won't have to pull zillions of seedlings out of the vegetable garden.
This is one of the world's worst annual weeds! If you don't want them by the dozens next year, you have to be diligent about pulling the plants up before they go to seed. If you neglect those growing alongside a trail, you will regret it come fall. The aggravating little needles will embed themselves in your clothing by the dozens every time you brush past the stems. Then, six months later, you'll go to wear that laundered sweater and there'll still be a few of the nasty little surprises hiding in the wool.