Introduction & History

Aztec sweet herb carries a secret in its tiny, cone-shaped flower heads — a sweetness 1,000 times more intense than sugar, packed into a low-growing ground cover that the Aztecs called tzonpelic xihuitl and used to sweeten medicines and chocolate drinks. The compound responsible, hernandulcin, was rediscovered by a Mexican chemist in 1985 and named after Francisco Hernández, the Spanish physician who first documented the plant in 1570. Despite its staggering sweetness, Aztec sweet herb never became a commercial sweetener — hernandulcin is heat-labile and bitter at high concentrations. But as a fresh garden nibble and herbal curiosity, it remains enchanting.

History & Origin

Native to Mexico, Central America, and the Caribbean, growing in disturbed areas, roadsides, and forest clearings from sea level to 1,800 m. Documented by Francisco Hernández during his 1570–1577 expedition to New Spain. Used by the Aztecs and Maya as a sweetener, cough remedy, and poultice for skin ailments. Introduced to Asia and Africa by colonial-era botanical gardens. Now naturalised in parts of Southeast Asia and tropical Africa.

Botanical Description

Low, spreading perennial, 10–30 cm tall and 60+ cm wide, with trailing stems that root at the nodes. Leaves are small (2–4 cm), ovate, toothed, and somewhat rough-textured, opposite, with a strong, sweet, slightly camphoraceous scent when crushed. Flowers are tiny, white, arranged in small oval spikes (1–2 cm) that emerge from the leaf axils. The entire plant has a ground-hugging, mat-forming habit.

Planting & Cultivation

Start from cuttings or nursery plants — seed is viable but slow and erratic. Plant after all frost danger in rich, moist soil, 30 cm apart. Full sun to partial shade. The trailing habit makes it suitable for hanging baskets, groundcover, or pot edges. In temperate climates, grow in containers and overwinter indoors.

Cultivation Details

Keep consistently moist — Lippia dulcis wilts quickly in dry conditions. Feed monthly during the growing season with liquid fertiliser. Pinch stem tips to encourage bushier growth and more leaf production. In tropical climates, it can become weedy — contain with regular trimming. The plant flowers prolifically; the tiny cone-shaped spikes are a continuous feature.

Climate & Hardiness

Tender perennial in zones 9–11. Frost-sensitive — killed below −2 °C. In temperate zones 7–8, grow as a summer annual or overwinter indoors. Thrives in warmth and humidity (20–35 °C). Tolerates light shade in hot climates. Can be grown year-round in a heated greenhouse or on a bright windowsill in cooler climates.

Seasonal Care

Spring: plant outdoors after last frost, or repot overwintered plants and move outside. Summer: water regularly, feed monthly, pinch for bushiness. Harvest leaves freely. Autumn: before first frost, pot up and bring indoors. Trim back by half. Winter: grow on a bright windowsill, reduce watering and feeding, keep above 10 °C.

Propagation

Stem cuttings root very easily — take 10 cm sections, strip lower leaves, and insert into moist compost or place in water. Roots appear in 7–10 days. Layering is even simpler: pin a trailing stem to moist soil and it roots at the node. Division of established plants in spring is also straightforward. Seed germination is slow and inconsistent — vegetative propagation is preferred.

Diseases & Pests

Whitefly and spider mites can be issues, especially indoors. Increase humidity and use yellow sticky traps for whitefly. Neem oil spray handles both pests. Root rot occurs in waterlogged soil — ensure good drainage in containers. Powdery mildew may appear in stagnant air. Generally pest-free outdoors in warm climates.

Culinary Uses

Chew a fresh leaf for an notable burst of sweetness. Add to herbal tea blends as a natural sweetener. Muddle into cold drinks, lemonade, and cocktails. Blend fresh leaves into smoothies. The sweetness works best cold or warm — high heat destroys hernandulcin. Not a cooking herb in the conventional sense; use as a fresh sweetening garnish. The Aztecs added it to chocolate drinks, and it still works beautifully in cold cacao preparations.

Medicinal & Aromatherapy

Traditional Mesoamerican use: cough remedy, bronchial congestion, and as a poultice for skin ailments. The sesquiterpene hernandulcin has been studied as a potential natural sweetener for diabetics — intensely sweet without caloric impact — but commercialisation stalled due to instability. The camphor content of some chemotypes makes the essential oil useful as a mild chest rub. Not to be confused with camphor-dominant chemotypes that are not sweet.

Container & Companion Growing

Container Growing

Excellent in hanging baskets, wide shallow bowls, and mixed herb containers. The trailing habit creates a cascading effect. Use rich, moisture-retentive potting mix. Water frequently — these plants drink a lot. Feed every two weeks in the growing season. Perfect for bringing indoors in winter as it remains attractive and functional on a windowsill.

Companion Planting

Use as a living mulch under taller tropical herbs like lemongrass and ginger. In containers, combine with other tropical flavour plants — pandan, Vietnamese coriander, and basil. The creeping habit fills in gaps between pot plants. The sweet-scented foliage may confuse some pests, though specific companion effects are undocumented.

Common Mistakes to Avoid

Letting the soil dry out — this plant wilts quickly and may not recover from severe drought stress. Using boiling water for tea, which destroys the sweet compounds. Confusing sweet-chemotype plants with camphor-chemotype plants (they look identical but taste very different). Not bringing plants indoors before first frost. Expecting dried leaves to retain sweetness (they lose most of it).

Harvesting & Preservation

Pick leaves and stem tips at any time — the sweetness is consistent throughout the plant's life. Use fresh for the best flavour; the sweetness diminishes when dried, as hernandulcin is volatile. Fresh leaves can be frozen in ice-cube trays with water. For tea, steep fresh leaves (5–6 per cup) in hot (not boiling) water — boiling degrades the sweet compounds.

Frequently Asked Questions

Seasonal Care Calendar