How much water does Bidens alba need?

A fast-growing annual or short-lived perennial (zones 9–11) reaching 24–48 inches (60–120 cm) tall and 18–30 inches (45–75 cm) wide. Stems erect to sprawling, branching freely, green to purple-tinged, square in cross-section. Leaves opposite, pinnately compound with 3–5 leaflets or simple in upper portions, each leaflet 1–2.5 inches (2.5–6 cm) long, toothed, medium green. Daisy-like flower heads 0.75–1 inch (2–2.5 cm) across with 5–8 white ray florets surrounding a yellow disc; produced continuously from late spring through frost. Fruit an achene with 2–4 barbed awns 0.2–0.4 inch (5–10 mm) long that adhere readily to clothing and animal fur. Produces hundreds of seeds per plant; self-seeds prolifically and can become invasive in warm climates. In frost-free zones, grows as a spreading perennial shrub.

Native Range

Native to the Caribbean, Central America, and tropical North America, including Mexico and Florida. Widely naturalized throughout the tropical and subtropical world, including southern Africa, Asia, and Pacific islands. In the United States, naturalized in Florida, the Gulf Coast, and Hawaii, where it grows in disturbed roadsides, fields, and waste ground.

Suggested Uses

Used in naturalized meadow plantings and pollinator gardens as a continuous-blooming nectar source. One of the primary nectar plants for honeybees and native bees in warm climates. The barbed seed heads are problematic near pedestrian areas or pet runs; plant in locations where seed spread is acceptable. In zones 9–11, requires containment to prevent invasive spread into natural areas.

How to Identify

Identified by opposite compound leaves with 3–5 toothed leaflets on square stems. Flower heads 0.75–1 inch (2–2.5 cm) across with 5–8 white rays and a yellow disc. Fruit with 2–4 stiff barbed awns that cling to fabric. Distinguished from Bidens pilosa (which lacks or has very short white ray florets) by distinct white ray florets. Distinguished from Bidens ferulifolia by compound rather than finely dissected ferny foliage.

Appearance

Size & Dimensions

Height2' - 4'

Width/Spread1'6" - 2'6"

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~28 weeks

Spring Summer Fall

Blooms from late spring through frost in annual culture, typically May through November in zones 6–9. In frost-free zones 9–11, blooms year-round. Individual flower heads last 3–5 days; plants produce new heads continuously at branch tips throughout the growing season.

Detailed Descriptions

Flower Description

White rays with yellow disc center

Foliage Description

Medium green, pinnately compound, toothed leaflets

Growing Conditions

Sun Requirements

Full Sun Partial Shade

Requires 6-12 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.5(Neutral)

357912

Soil Types

loam sand clay

Drainagewell drained

Water & Climate

Water Needs

Low

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Direct sow after last frost or transplant established plants after soil warms to 60°F (16°C). Grows in a wide range of soils including poor, dry, and disturbed ground; performs in nutrient-poor conditions without supplemental fertilizer. Water during establishment; established plants are drought tolerant and require no irrigation in areas receiving 1 inch (2.5 cm) or more of rainfall per week. No significant pest or disease problems in most regions. Deadhead or remove plants before seed matures to prevent prolific self-seeding; a single plant can produce 3,000–6,000 seeds. In zones 9–11, plants spreading beyond intended areas may be difficult to control due to vigorous resprouting from root crowns after cutting.

Pruning

Cut back by half in midsummer if plants become sprawling, to encourage compact regrowth and fresh flowering. Remove or deadhead before seeds mature to reduce self-seeding. In zones 9–11, cut to 6–8 inches (15–20 cm) in late winter to renew growth. In frost-prone zones, plants are killed by frost and do not require overwintering pruning.

Pruning Schedule

summer