Blue Daze (Evolvulus glomeratus), also known as Hawaiian Blue Eyes, is a popular ornamental plant admired for its continuous display of vibrant sky-blue flowers. This low-growing species creates a dense, sprawling mat of silvery-green, fuzzy foliage. Its trailing nature makes it a favored choice for ground cover or as a “spiller” plant cascading over the edges of containers. Native to tropical and subtropical regions of South America, its survival depends heavily on warm temperatures.
Classification: The Annual vs. Perennial Reality
Blue Daze is botanically classified as a tender perennial subshrub, meaning it lives for more than two years in its native environment. Its ability to survive year-round is entirely dependent on sustained warm temperatures. It is reliably perennial only in USDA Hardiness Zones 9 through 11, where winter temperatures remain above freezing.
In these warm regions, the plant remains evergreen and blooms almost continuously throughout the year. Outside of these zones, the delicate root system and foliage cannot tolerate frost or freezing conditions. Gardeners in cooler climates, such as Zone 8 and lower, must treat Blue Daze as a functional annual. A hard freeze will kill the plant, necessitating replanting each spring.
Ideal Growing Conditions
Blue Daze requires environmental conditions that allow it to thrive during its active growth period. This plant demands full sun exposure to maintain a dense, compact form and produce prolific blooms. A minimum of six to eight hours of direct sunlight is necessary, as insufficient light leads to thin, elongated stems and reduced flowering.
The plant prefers soil that drains exceptionally well. It tolerates a wide range of soil types, including sandy soils, but it cannot withstand constantly wet roots. Overwatering or planting in heavy soil is the most common cause of failure, often leading to root rot. Once established, it exhibits good drought tolerance, requiring less frequent watering than many other ornamentals.
During intense heat, regular watering is recommended to sustain flowering, but the soil surface should be allowed to dry completely between applications. Fertilization should be done monthly during the warm growing season with a balanced, all-purpose liquid feed to support continuous flower production.
Overwintering Strategies
For gardeners outside of Zone 9, preserving Blue Daze requires proactive measures before the first frost. The most straightforward method is to grow the plant in a container that can be easily moved indoors. It should be brought inside once nighttime temperatures consistently drop below 50 degrees Fahrenheit.
When moved indoors, the plant enters a period of semi-dormancy and requires a bright location, such as a south-facing window. Watering frequency must be reduced, allowing the potting mix to dry out significantly between applications. Fertilization should be suspended entirely until active growth resumes in the spring.
An alternative strategy is to propagate the plant by taking cuttings in late summer to ensure the genetics survive the winter. Softwood stem cuttings can be rooted easily in a sterile potting mix or water. These new plants are easier to manage and overwinter on a bright windowsill, ready to be planted out once all danger of frost has passed.