White zinnia (Zinnia acerosa) is a small desert shrub that lives in the southwestern United States and northern Mexico. It develops gnarled, woody branches and rarely exceeds 16 cm in overall height. Thanks to its hardy nature and long blooming period, white zinnia has become a popular ornamental plant in dry regions. The flowers also commonly attract butterflies.
I. Appearance and Characteristics
Zinnia acerosa is a low-growing perennial flowering plant native to the Southwestern United States and Northern Mexico. Common names include desert zinnia, wild zinnia, white zinnia, and spinyleaf zinnia. It is a popular landscape plant in the southwest due to its low water use and long bloom period. The flowers also serve as a food source for southwestern butterflies.
In the United States, Zinnia acerosa grows in Arizona, Utah, New Mexico, and Texas. In Mexico, it has been found in Sonora, Chihuahua, Coahuila, Durango, Nuevo León, Zacatecas, and San Luis Potosí.
Zinnia acerosa is a small, branching subshrub up to 16 cm (6.4 inches) tall. Leaves are very narrow, sometimes needle-shaped, up to 2 cm (0.8 inches) long. The plant produces flower head one per stem, each head with 4-7 yellow or white ray florets surrounding 8-13 yellow or purple disc florets.
II. How to Grow and Care
Sunlight
White zinnia thrives best in conditions of full sun, receiving at least 6 to 8 hours of direct sunlight daily for optimal growth. As a sun-loving species, deviations from these light conditions can lead to subpar growth and reduced vitality. While white zinnia can tolerate some variation in light intensity, prolonged exposure to lower light conditions may result in leggy plants with fewer blooms. Outdoors, white zinnia should be planted in areas that receive unobstructed sunlight throughout the day. They are not typically grown indoors due to their high light requirements. The plant is well-adapted to bright environments, and it will likely exhibit strong growth and abundant flowering when its light preferences are met.
Temperature
White zinnia is originally from Mexico. It likes hot weather and is sensitive to low temperatures. It pretty much needs reseeding every year. The best temperature range for it is 18 to 25 ℃. When winter temperatures drop below 13 ℃, it stops growing and its stems and leaves dry up and turn yellow. However, it can tolerate high temperatures above 30 ℃ and grow and bloom normally. Some heat-resistant varieties can even tolerate temperatures above 35 ℃. The temperature needs to stay above 15 ℃ for seedlings; temperatures below that negatively affect growth. White zinnia doesn’t require much water and is drought-tolerant.
Watering
White zinnia is a plant that thrives in arid conditions, demonstrating significant drought tolerance. It typically requires watering once every 2-3 weeks to maintain its water balance. This plant’s preference for dry environments suggests it would be best suited to indoor settings where humidity levels can be easily controlled. White zinnia’s growth cycle, which involves a long dormancy period, further underscores its low water requirements.
Soil
The only soil requirement of white zinnia is good drainage. Its roots don’t like moist soil. Too much water in the soil can cause powdery mildew. If possible, use soil with neutral pH value.
Fertilizing
White zinnia thrives with regular fertilization, favoring balanced nutrition fertilizers during the growing season for robust growth and high-nitrogen fertilizers for vegetative vigor. Monthly application at manufacturer-specified rates is optimal, tapering off in late summer to prepare for dormancy. Over-fertilization risks growth at the expense of blooms. Seasonal variance necessitates reduced winter feeding. For effectiveness, water soil before and after applying granular fertilizer to prevent root burn and to aid nutrient absorption.
Planting Instructions
Sowing is the simplest way to propagate white zinnia. Indoor sowing can take place 4-6 weeks before the last frost every spring. Of course, direct sowing can also be performed outdoors, but it requires warmer soil temperature after the last frost. White zinnia seedlings are sold at almost every garden center, so you can purchase those directly and save yourself the trouble of sowing.
Pruning
Pinch white zinnia seedlings back when they are young. Nip the buds on the branch tips to promote lush growth of the stems and leaves, so the plant grows into a shorter, more stocky, exuberant form. For taller varieties, support the plant with sticks to prevent it from growing obliquely or creeping on the ground.
Deadhead the spent flowers to reduce unnecessary nutrition consumption, so the rest of the flowers flourish and flower longer. To deadhead, cut below the flowers and above the leaves so that the plant continues to grow and sprout new flower buds.
Propagation
A member of the Asteraceae family, white zinnia is a resilient flowering perennial suitable for xeriscaping in dry regions. It thrives in full sun with well-drained soil and responds well to propagation by cutting. The technique involves taking healthy, non-flowering stems, making a clean cut below a node, and planting them in a moist, well-draining growing medium. Rooting hormone can enhance success, but white zinnia generally roots easily, maintaining high genetic fidelity to the parent plant.
Transplanting
The optimal time to transplant white zinnia is when the chill of winter gives way to the gentle warmth of the vernal season, facilitating root establishment. Pick a sunny spot with well-draining soil and add compost for best results.
III. Harvesting and Storage
With proper care, white zinnia flowers from summer through fall. Harvest the flowers when the temperature is low and humidity is high, generally in the morning. Harvesting in the cool of the day, when plants have the most moisture, helps the cut flowers last longer.
After the flower season, get rid of the withered plants and grow something else for a change. For rare white zinnia varieties, consider keeping some withered flowers from one or two plants to harvest the seeds for sowing next year.