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Romerillo

Bidens alba · Asteraceae

The gardener's calendar

The right move for September

Ideal time to plant romerillo: set it out when the soil is neither frozen nor waterlogged, and water generously as it establishes.

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ID card

Family
Asteraceae
Type
Annual or perennial herb depending on climate
Flowering
July to October
Adult size
60 to 90 cm in height
Foliage
Deciduous, finely divided
Hardiness
Frost-sensitive, tropical to subtropical climate
Origin
Tropical and subtropical America
Growth
Fast

Care

Watering

Keep the soil regularly moist without waterlogging, especially during active growth. Reduce watering in autumn and winter if the plant slows down. Prefer watering in the morning to avoid stagnant moisture that promotes fungal diseases.

Light Exposure

Bidens alba thrives in full sun or partial shade. A sunny exposure (at least 6 hours of direct light) promotes abundant flowering. In very hot regions, light afternoon shade can prevent water stress.

Soil and Drainage

Prefer well-draining soil, rich in organic matter, slightly acidic to neutral. Avoid water accumulation which causes root rot. A potting soil and compost mix with good drainage is ideal.

Pruning and Maintenance

Pinch young stems to encourage a bushier form. Remove spent flowers regularly to extend blooming. At the end of the season, cut back stems if the plant becomes woody or too invasive.

Fertilizing

Apply a balanced or potassium-rich fertilizer every 15 days during growth and flowering. Reduce or stop fertilizing in winter. Avoid excess nitrogen which promotes foliage at the expense of flowers.

Diseases and Pests

Watch for fungal diseases in case of excessive moisture (powdery mildew, rot). Regularly aerate the plant and avoid watering the foliage. Aphids and whiteflies may occasionally infest young shoots; treat with non-chemical means as a priority.

Did you know?

Bidens alba is mainly known for its tiny fruits with hooked barbs (achenes) that cling to clothing and animal fur for dispersal – hence the nickname 'needle grass'. Traditionally used in certain cultures for its medicinal properties, it remains a useful plant in ecological gardening to promote biodiversity.

Where to buy it

Plant in spring or early autumn, avoiding spells of intense heat. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, April, May, September.

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Tips generated and checked by Viridia — adapt them to your local climate.