Zones for Rudbeckia Gloriosa

Growth Characteristics

• Common black-eyed Susans are rather short-lived perennials -- three to five years at most --- that develop a basal tuft of fuzzy leaves and send up tall flower stems in summer. Across its large natural range, where soils and climate vary greatly, this wildflower endures as a perennial, two-year biennial or as an annual. Seeds that sprout in early spring will bloom later that summer and may or may not overwinter to grow and bloom again the following year.

Winter Hardiness

• Expect a common black-eyed Susan to act more as a biennial or short-lived perennial in U.S. Department of Agriculture plant hardiness zones 3 through 7. It may also be grown as an annual depending on the needs and habits of the gardener. Plants do not overwinter well in overly mild winter climates in the southernmost tier of the United States. A cold winter keeps the plants fully dormant without a depletion of carbohydrates in the roots.

Summer Heat

• The American Horticultural Society developed the AHS Heat-Zone Map to help gardeners determine what summertime heat is beneficial or detrimental to the long-term health of plants. Common black-eyed Susans grow best in areas where no more than 90 days of temperatures above 86 degrees Fahrenheit occur. This correlates to heat-zones 7 through 1. However, the common black-eyed Susan may still be grown across all parts of the United States.

Regional Insight

• While parts of Canada and Alaska may be too cold for common black-eyed Susan plants to overwinter as biennials or perennials, the plants may be grown as an annual and placed outdoors when there's no threat of frost. Conversely, while the summer heat and lack of winter cold doesn't behoove long-term vitality in the desert Southwest or in Florida, seeds may be sown there in autumn and allowed to grow across winter and bloom in spring before summer heat withers plants.