Spanish Needle Control: Tips On Managing Spanish Needle Weeds
What is Spanish needle? Although Spanish needle plant (Bidens bipinnata) is native to Florida and other tropical climates, it has naturalized and become a major pest across much of the United States. Spanish needle weeds aren’t all bad; the plants display attractive foliage and tiny yellow centered white flowers that attract honeybees, butterflies, and other beneficial insects.
The downside is that the plant is extremely aggressive and produces needle-like seeds that cling to everything they touch, including hair, fabric, and fur. When you consider that one plant can produce 1,000 prickly seeds, you can understand why Spanish needle plant isn’t a welcome visitor in most gardens. If this sounds familiar, keep reading to learn about Spanish needle control.
Controlling Spanish Needles
Young Spanish needle weeds aren’t difficult to pull when the ground is moist, and unless you have a huge infestation, hand-pulling is the most effective and safest solution. Work carefully and use a shovel or spade, if necessary, to get the long, tough taproot. The key to success is to pull the weeds before they have a chance to go to seed – either before the plant blooms or shortly after – but always before the blooms wilt.
Don’t expect to eradicate Spanish needle plant at first try. Keep pulling the seedlings when they are young and tender; you’ll eventually gain the upper hand.
If you have a large infestation, mow the plants periodically so they have no opportunity to develop flowers and go to seed. You can also gain Spanish needle control by spraying individual plants with products containing glyphosate.
Alternatively, spray large infestations with a herbicide that kills broad-leaf weeds, such as 2,4-D. Keep in mind that due to high toxicity and dangers to people, animals, and the environment, herbicides should always be a last resort.
Note: Any recommendations pertaining to the use of chemicals are for informational purposes only. Specific brand names or commercial products or services do not imply endorsement. Chemical control should only be used as a last resort, as organic approaches are safer and more environmentally friendly.
Needles og seeds
Aster family (Asteraceae)
Description: This plant is a summer annual about 2-5′ tall; it is more or less erect and branches occasionally. The stems are green or reddish green, angular, strongly veined, and hairless (or nearly so). The leaves are mostly opposite; their blades are up to 8″ long and 4″ across, while their petioles are up to 2″ long. The leaf blades are double- or triple-pinnate, medium green, and hairless (or nearly so). The segments of the blades are ovate, lanceolate, or oblanceolate with blunt tips and wedge-shaped bottoms; the margins of these segments are irregularly cleft or dentate. Overall, the leaf blades have a fern-like appearance. The upper stems terminate in individual flowerheads on long peduncles. Each flowerhead is about �” long and �” across; it has numerous disk florets in the center and 0-5 ray florets along its upper margin. The disk florets have corollas that are golden yellow and tubular in shape; each corolla has 5 tiny lobes along its upper rim. The yellow ray florets are petal-like; they are about 1/8″ (3 mm.) long and oval to oblong in shape. Some flowerheads may lack petal-like extensions of the ray florets altogether. The base of the flowerhead is surrounded by green bracts; the linear inner bracts are much longer (about 1/3″ or 8 mm. in length) than the outer bracts. The blooming period occurs during the late summer or early fall. Each flowerhead is replaced by a seedhead that is globoid in shape and spans about 1″ across. The long narrow seeds (achenes) spread outward from the center in all directions. Each mature seed is linear in shape, 4-angled, and dark brown; it has 2-4 short awns at its tip. Each tiny awn has downward-pointed barbs. The root system consists of a branching taproot. This plant spreads by reseeding itself.
Cultivation: Partial or dappled sunlight, moist to mesic conditions, and a fertile loamy soil are preferred. However, this robust plant can adapt to a wide range of environmental conditions. The size of individual plants varies significantly, depending on moisture levels and soil fertility.
Comments: The arrangement of the trident-shaped seeds into globoid seedheads is very striking. The common name derives from the appearance of these seeds. Among the many Bidens spp. in Illinois, Spanish Needles is the oddball of the group. The seeds of Spanish Needles are longer and usually more slender than those of other Bidens spp. Spanish Needles also has differently shaped leaves – they are more pinnately divided into smaller leaf segments than the leaves of other Bidens spp. (which are sometimes simple, rather than compound). Finally, Spanish Needles seems to prefer drier habitats; other Bidens spp. are more likely to be found in various wetland habitats.
Fungal endophytes in seeds and needles of Pinus monticola
Using a sequence-based approach, we investigated the transmission of diverse fungal endophytes in seed and needles of Pinus monticola, western white pine. We isolated 2003 fungal endophytes from 750 surface-sterilized needles. In contrast, only 16 endophytic isolates were obtained from 800 surface-sterilized seeds. The ITS region was sequenced from a representative selection of these endophytes. Isolates were then assigned to the most closely related taxa in GenBank. Although 95% of the endophytes in needles from mature trees belonged to the Rhytismataceae, 82 unique ITS sequences were obtained from at least 21 genera and 10 different orders of fungi. Significantly, none of the endophytes in seed were rhytismataceous (chi(2) = 180; P < 0.001). Similarly, needles of greenhouse seedlings yielded only non-rhytismataceous isolates, whereas seedlings of the same age that had naturally regenerated near older white pines in roadless areas were colonized by rhytismataceous endophytes almost to the same extent as in mature trees. Only one of 17 rhytismataceous isolates were able to grow on a medium containing only 0.17% nitrogen, whereas 25 of 31 non-rhytismataceous endophytes grew. Rhytismataceous endophytes are dominant in needles of P. monticola, but they appear to be absent in seed, and unlikely colonists of nitrogen-limiting host tissues such as the apoplast.
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