Bidens are flowering plants known for their cheerful, daisy-like blooms. While often yellow or orange, newer varieties also come in pink, gold, and white. Their prolific blooming and trailing or mounding habits make them popular for garden beds, containers, hanging baskets, and as groundcovers. They also attract pollinators like bees, butterflies, and hummingbirds.
Understanding Bidens: Perennial or Annual?
Whether Bidens are perennials or annuals depends on the specific species and the climate. The genus Bidens includes approximately 230 species, both annual and perennial. In warmer regions (USDA hardiness zones 8-11), many Bidens varieties behave as true perennials, returning year after year. In these frost-free or mildly cold climates, they may stop blooming in late fall and winter but keep their green foliage, with flowers returning in spring.
In colder climates with freezing temperatures, Bidens are treated as annuals because they cannot survive winter. These are often called “tender perennials.” If temperatures drop below 40°F, Bidens plants will likely perish, requiring replanting each spring. Understanding your local climate zone is important for how a Bidens variety will perform.
General Cultivation and Care
Bidens thrive in conditions that promote abundant flowering. They prefer full sun, needing at least six hours of direct sunlight daily for optimal blooming. Inadequate light can result in fewer blooms and leggy growth. Well-draining soil is important to prevent root rot, and Bidens perform best in rich, humus soil that is neutral to slightly acidic.
While Bidens are drought-tolerant once established, consistent moisture promotes continuous blooming. About an inch of water per week, allowing the soil to dry slightly between waterings, is sufficient. For vigorous growth and prolific flowering, apply a balanced, general-purpose fertilizer monthly or a slow-release granular fertilizer at planting. Most modern Bidens varieties are self-cleaning, so deadheading is not needed, though pruning can maintain shape or encourage bushier growth.
Winter Care for Perennial Bidens
For Bidens grown as perennials in USDA zones 8-11, specific care practices help. In borderline zones, applying a 2-inch layer of organic mulch (like straw or shredded leaves) around the plant can insulate roots and moderate soil temperatures, protecting them from cold. Apply this mulch after several hard frosts, once the ground has cooled.
For potted Bidens in colder climates, bringing them indoors before the first frost is an overwintering option. Indoors, place plants in a bright, sunny location and reduce watering significantly. Pruning before bringing them inside can manage size and promote new spring growth. However, in very cold zones, Bidens are often best treated as annuals and replanted each spring, as survival can be challenging.