The Genus Bidens
This is a large genus of herbaceous plants ranging over warm and cool climates of Africa, Asia, Australia, Europe, North America, and South America. Some effort has gone into hybridizing garden plants from this genus but they are rarely found in local nurseries or landscapes.
The aster family, Asteraceae, is a huge genus of herbaceous and woody plants that is found around the world. Only the orchid family rivals the number of species in this family. They may be annuals, herbaceous perennials, shrubs, trees or vines. Important members of the family include tickseed (Coreopsis,) blanket flower (Gaillardia,) sunflower (Helianthus,) goldenrod (Solidago,) marigold (Tagetes,) ironweed (Vernonia) and zinnia (Zinnia.)
This is a native annual or herbaceous perennial (depending on the winter low temperature) to three feet tall or more. Small white daisies with yellow disks can be produced throughout the year, flowering heaviest in late summer and fall. It grows in sun or part shade, in any reasonably well-drained soil. They are drought tolerant once established. Flowers are attractive to butterflies. This plant should be used in naturalistic or wildlife gardens but it has two habits that make it undesirable for formal gardens. The seeds stick to clothing and pets’ fur, and the plant is fast growing and difficult to pull. It ranges naturally across most of the Coastal Southeast. According to the USDA, it is absent from Texas and Mississippi.
The scientific name of this plant is thoroughly confused with Bidens pilosa in popular literature. This plant has been lumped under the name B. pilosa in the past and some botanists today continue to lump them together. A 1986 article by Robert Ballard in the American Journal of Botany describes the separation of these species and the differences between them. Bidens pilosa seeds have three to five barbs and B. alba has two or none. Remember that daisies have sterile ray flowers that look like petals. These ray flowers are absent or about an eighth of an inch long in B. pilosa while the ray flower of B. alba is one quarter to over one half inch long. Bidens pilosa is reported to be an annual, even in warm climates.
Bidens alba is not available in nurseries. Plants are grown easily by seeds and summer stem cuttings.
Plants in my zone 9a gardens are naturally occurring natives. They are perennial some years and flower from late spring to the first hard freeze. A winter low in the upper teens killed plants in the open. Volunteer seedlings replace lost plants in the following spring. I encourage this plant in certain sites in my home garden and at the University of North Florida but I work to control it in the more formal garden areas.
This plant is native to much of the southern United States, ranging from California to Massachusetts. It differs from Bidens alba in having a doubly divided leaf. The daisies tend to have only a few ray flowers which may be yellow or white. This plant attracts butterflies and other pollinators but tends to be weedy and has the seeds that stick to clothing like B. alba. It may be most appropriate for naturalistic gardens and natural areas.
other Bidens species
Selections of Bidens ferulifolia are cultivated in gardens. It is native to the American Southwest and Mexico. They are drought tolerant, creeping plants. I have not tried this species, yet.
Some yellow-flowered species grow naturally in the Coastal Southeast. The ones I know are annuals that grow in moist or swampy conditions. Bidens laevis has smooth, simple leaves. It flowers in fall. Bidens mitis has compound leaves with deeply dissected leaflets. It flowers in fall, also, at about the same time as B. laevis.
I have not seen these plants for sale. They should be encouraged and enjoyed wherever they grow naturally. They may be propagated by seeds.