© Богданович Светлана, some rights reserved (CC-BY-NC) · iNaturalist
Overview
Blackstonia spp. is a genus of annual herbs in the gentian family (Gentianaceae), native to Europe, the Mediterranean region, and western Asia. The most familiar species, Blackstonia perfoliata, called yellow-wort, grows on chalk and limestone grassland, dunes, and other open calcareous ground. Plants form an erect, branching stem 6-18 inches (15-45 cm) tall, smooth and grey-green with a waxy bloom. The paired stem leaves are joined at their bases so that the stem appears to pass through a single leaf, a feature that makes the plant easy to recognize. From summer into early autumn, the branched stems carry bright yellow flowers about 0.5-0.6 inch (12-15 mm) across, with six to eight narrow petals that open in sunshine and close in dull weather. Blackstonia spp. completes its life cycle in a single year, setting small capsules of numerous tiny seeds. It needs open, sunny, lime-rich sites and does not persist on acid soils or in dense vegetation. Because it is annual and self-seeding, populations shift from year to year with conditions.
Native Range
Native to Europe, the Mediterranean Basin, and western Asia, on chalk and limestone grassland, dunes, quarries, and other open calcareous ground.Suggested Uses
Grown in wildflower meadows, chalk and limestone grassland restoration, and gravel or rock gardens on alkaline soils. It combines with other short-lived calcareous grassland flowers.How to Identify
Appearance
Size & Dimensions
Height6" - 1'6"
Width/Spread4" - 10"
Colors
Flower Colors
Foliage Colors
Bloom Information
Detailed Descriptions
Foliage Description
Grey-greenGrowing 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
Water & Climate
Water Needs
Drought Tolerance
Drought tolerant when established