St. John's Wort
Plant H. calycinum 18 inches apart in a light loam soil, preferably in full sun, though it is tolerant of hot, dry soils and light shade. Soil should be enriched with organic matter. Space 12 to 15 inches apart in average, well drained garden soil.
South of zone 5, cut old weak shoots back to the ground in the spring and prune remaining shoots back to 10-12 inches. Zone 5 and north, prune back to ground level in early spring. Does not perform optimally where temperatures drop below –5°F. Mulch with leaf mold every other year.