Salvia uliginosa

bog sage

Fast growing, herbaceous, evergreen perennial, native to Brazil, Uruguay, and Argentina. Four-ribbed stems with somewhat sticky, lanceolate, toothed leaves. Azure blue with white, two-lipped flowers, 2 cm long, in whorls arranged in spikes, during summer and autumn.

Prefers a sunny or partially shaded position in any type of soil. Really likes moist soils, but tolerates, and usually spreads less vigorously in, dry conditions. Generally disease-free. Cut back to near ground level after flowering. Spreads by means of underground runners. Keep an eye on these and remove them where they are not wanted. Tolerates moderate frosts. Frost-hardy throughout New Zealand.

Reaches a height of about 1.8 m in one growing season, so plant in the back of borders for a gorgeous, long-lasting display of blue. Attracts butterflies.