A flowering plant that requires two years to complete it's life cycle and then dies. However some biennials may complete their life cycle in as little as 3-4 months, depending on weather and climate conditions. Whether a plant is cold hardy or not is not connected to being an annual, perennial or biennial.
Verbascums make a presence in the wildflower or cottage garden and mixed border, whether it be this common mullein, or another species with showier flowers. Verbascums can be either biennial or perennial, but will make enough seeds you’ll never be without. Some are drought tolerant and thrive in poor, but well drained soil, others may need medium water use and a richer soil.
Bigelow's tansyaster is easy to confuse with Tahoka daisy but is not as showy. Bigelow's aster is a fall blooming biennial, with far fewer purple rays and a smaller, yellow brown center disk. It populates plains in Colorado, Arizona and New Mexico. In the fall, whole fields will wear a purple haze due to this tansyaster.
Old fashion garden and English cottage garden herbaceous perennial that works well in the Southwest Cottage Garden. Hollyhocks are considered to be either a biennial or perennial. They produce copious seed but are not considered invasive or troublesome. Plant seed in the fall, or early spring. Avoid watering the foliage if irrigating, a drip system works better that above ground sprinklers.
Reseeding biennial, native to Texas, and the southeastern US. The red tubular flowers make it attractive to hummingbirds. The upright stalks are brittle and break off easily.
Standing cypress will flower the first year, and may, or may not come back a second year, but you should see some seedlings. Transplant those. The glossy green foliage to the right in this picture belongs to Anisacanthus quadrifidus wrightii, flame acanthus.
Salvia argentea is a first class drought tolerant biennial to add texture to your xeristrip. Light gray green tomentose (hairy) foliage adds contrast against accent rocks. This biennial will flower the second year, but I could do without the sticky, and somewhat unsightly stalk whose white flowers open in succession and quickly turn brown. Cutting off the stalks only encourages the plant to send up more sticky stalks. The leaves of the plant may appear to mimic Lamb’s Ears, however, they are not tough and resilient, tears easily, and are shredded by hail.