Pterocaulon pycnostachyum
blackroot
Overview
Pterocaulon pycnostachyum is an erect perennial herb in the aster family (Asteraceae), growing 12-32 inches (30-80 cm) tall from a thickened, dark-skinned rootstock that gives rise to the common name blackroot. The stems are winged, their edges bearing thin flanges that run down from the bases of the leaves. Leaves are alternate, lance-shaped to elliptic, 1.5-4 inches (4-10 cm) long, dark green and nearly hairless above but densely white-woolly beneath. The small flower heads lack ray florets and are packed into a single dense, cylindrical terminal spike 1.5-4 inches (4-10 cm) long, the individual heads cream to grayish-white. Flowering stems rise from a basal crown each season, and the plant regrows from its perennial root after dormancy or fire. The fruit is a tiny, bristle-tipped achene dispersed by wind. The woolly white undersides of the leaves and the winged stem set it apart from other upright Asteraceae of the same sandy habitats. One limitation in the garden is its narrow tolerance for soil moisture, since it is adapted to sharply drained sands.
Native Range
Pterocaulon pycnostachyum is native to the southeastern United States, where it grows in sandy pinelands, scrub, and open woods along the coastal plain from North Carolina to Florida and west to the Gulf states. It is closely tied to fire-maintained longleaf pine communities.Suggested Uses
This species is grown chiefly in native plant restorations, pine-savanna gardens, and sandy xeric beds where its drought tolerance matches the site. The root has a documented history of use in regional folk medicine. As a reference example it represents the winged-stemmed Pterocaulon spp. group of the Asteraceae.How to Identify
Appearance
Size & Dimensions
Height1' - 2'8"
Width/Spread1' - 1'6"
Bloom Information
Flowering occurs mainly from late spring into summer, roughly May through July, when the cylindrical spikes of cream to grayish heads appear at the stem tips. Bloom often follows soon after fire has cleared competing vegetation. Wind-dispersed seed matures within several weeks of flowering.
Detailed Descriptions
Flower Description
cream to grayish-whiteFoliage Description
dark green above, white-woolly beneathGrowing Conditions
Sun Requirements
Requires 6-12 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight