Salt Heliotrope

Salt heliotrope (Heliotropium curassavicum) is a sprawling plant that is native to much of North and South America and has spread to other continents. The long narrow sprays of flowers uncoil as the bloom progresses. The small, white flowers have yellow throats that turn purple as they age.

Salt heliotrope is associated with a wide range of vegetation types and is often found in damp and disturbed areas, especially those that are slightly alkaline or saline. In some places, this lovely flower is considered a weed.

Description ^2,4,11,59

Salt heliotrope is a sprawling perennial herb that is usually less than a foot (30 cm) high but may occasionally work its way several feet up through neighboring shrubs. Leaves are bluish green and somewhat fleshy; they lack hairs but may be thinly covered with a whitish powder. Leaves are oval to oblanceolate, 1/4-1 1/2 inches (1-6 cm) long, with smooth margins.

Flowers are produced along a gradually uncoiling stalk (a “scorpioid cyme”); stalks are often paired, occasionally in threes. Flower buds develop in the center of the coil and new flowers appear in alternating rows along the outer part of the uncoiling stalk. Seedpods develop along the older, straightened stalk. At Torrey Pines, flower stalks are generally less than 4 inches long.¹ However, at the San Elijo Lagoon Nature Center, one exuberant plant produced flower stalks more than 13 inches (35 cm) long, with seven blooming flowers, at least seven buds yet to open and evidence of 139 previous flowers.

Petals are united into a bell, about 1/4″ (0.6 cm) wide with five flaring lobes. Flowers are bisexual with five stamens and one green, mushroom-shaped pistil. In the Reserve, young flowers are white with greenish-yellow throats; throats turn purple as the flowers age. The primary bloom period extends through spring and summer, usually March – October.¹

Each flower produces a fruit that separates into 0-4 nutlets. However seed set is low and rarely does a flower produce all four nutlets. Reproduction is more often by shoots arising from the wide-spreading roots than by seeds.

Classification  

Salt heliotrope is a dicot angiosperm in the borage family (Boraginaceae).² This family is large and, until recently was split it into several families, one of which was a one-genus family the heliotrope family (Heliotropiaceae).^41,59

Members of the borage family, as currently recognized, are characterized by flowers that are produced along a coiled stalk and by a fruit that splits into four one-seeded nutlets.^2,44 Many of the best-known members of this family are not native, including the garden heliotrope and forget-me-not, and the culinary borage, which is used in soups and salads.⁴¹

Other members of the borage family in the Reserve include common phacelia (Phacelia distans), coast fiddleneck (Amsinckiaintermedia), fiesta flower (Pholistoma auritum) and popcorn flower (Cryptantha spp.).⁴⁸

In California the species H. curassavicum consists of a single variety var. oculatum,^2,7 sometimes considered to be a subspecies.⁶⁷However, some taxonomists no longer recognize subdivisions of this species.⁴

Ecology  

Like many members of the borage family, salt heliotrope produces organic compounds called pyrrolizidine alkaloids (PAs) which are thought to have been developed by the plant as a defense against insect herbivores.⁴¹ PAs also taste bad and cause liver damage in some vertebrates, including humans, which offers the plant protection against vertebrate grazers. However, adaptations often beget counter-adaptations, and some insects have become resistant to PAs and not only feed on the plants but store the PAs as a defense against their own vertebrate predators.⁵⁹

Human Uses  

The Kumeyaay boiled the roots of salt heliotrope into a medicinal tea to regulate menstruation.¹⁶ Spanish settlers made a powder from the leaves and blew this into wounds to promote healing.²³ A purple dye can be made from this plant.³⁴

The common names, Chinese purslane, and Chinese pusley originated in the 1800s when Chinese immigrant workers harvested salt heliotrope greens to supplement their diet, much as common purslane (also called pusley) is used today.¹¹

WARNING: Given the toxic nature of salt heliotrope¹²⁶ (see Ecology), ingestion for any reason is not advised.

Interesting Facts  

Salt heliotrope is a butterfly magnet.⁵⁹ A 34-year butterfly study in Central California¹²⁷ has found a variety of butterflies that regularly visit the flowers, including the locally common gray hairstreak, acmon blue, and buckeye. The garden heliotrope, in the same genus, is often recommended for butterfly gardens.¹²⁸ However, we have found no record of local butterfly species using salt heliotrope as a host plant.