Amaranth is a versatile annual plant cultivated for its nutritious grain, edible leaves, and striking ornamental plumes. Understanding the timing of its flowering is important for successful cultivation, whether the goal is harvesting the pseudo-cereal seed or maximizing the visual display of the plant’s colorful flower heads. The life cycle of amaranth, from germination to the onset of blooming, is a predictable process largely governed by the plant’s genetics, but it can be significantly altered by environmental signals.
Typical Timing of Amaranth Flowering
Amaranth’s transition from vegetative growth to the reproductive phase is measured by Days to Maturity (DTM). The time it takes for the plant to begin flowering after planting can vary widely depending on the specific species and cultivar. Grain-producing varieties often require 60 to 90 days from the time the seed is sown until the first flowers appear.
Cultivars bred for ornamental purposes, such as “Love-Lies-Bleeding,” generally bloom in late summer to early autumn in temperate climates. Since most planting occurs after the last frost in late spring, the plant enters its bloom phase once the extended daylight hours of summer begin to shorten. This timing ensures the seed-setting process can complete before the first hard frost of the fall. The entire life cycle, from planting to full maturity for seed harvest, typically takes 40 to 50 days in quick-maturing varieties, but can take longer, up to 90 days or more, for grain production.
The flower heads, known as panicles, begin as small, inconspicuous growths before rapidly elongating into the large, colorful tassels or plumes characteristic of the plant. This development is a clear indicator that the plant has shifted its energy from producing leaves and stems to preparing for seed production. The appearance of these structures marks the end of the main vegetative growth period and signals the start of the final reproductive phase.
Environmental Influences on Bloom Time
The most influential external factor controlling amaranth blooming is the length of the day, a phenomenon known as photoperiodism. Most cultivated grain amaranths are short-day plants, meaning they initiate flowering when the period of uninterrupted darkness exceeds a certain threshold. This triggers the plant to flower as the days grow shorter after the summer solstice, promoting blooming in late summer and early fall.
Varieties differ in their sensitivity to day length. Some Central American accessions show a high degree of photoperiod sensitivity, which delays flowering under the long days of a northern summer. Other cultivars have been bred to be less sensitive, allowing them to flower earlier and set seed more reliably in regions with shorter growing seasons.
Temperature also plays a role, as amaranth thrives in warm conditions with ideal temperatures between 70°F and 85°F. Extreme heat or drought stress can sometimes induce earlier flowering, a survival mechanism where the plant attempts to produce seed before it dies. Conversely, a lack of sufficient heat or an early cold snap can delay blooming or prevent photoperiod-sensitive varieties from flowering entirely in temperate zones.
Significance of the Flower Head for Harvest
The emergence of the prominent flower head is a signal to the grower that the plant is moving toward its final harvestable stage. For ornamental amaranth, the dense, brightly colored panicles are the main attraction, and they are typically harvested for cut flowers when about three-quarters of the tiny individual flowers are open. The flower head’s ability to retain its color and structure is why the plant’s name comes from the Greek word meaning “one that does not wither.”
For those cultivating amaranth for grain, the flower head is the site of seed development. After the initial blooming period, the flower head must be allowed to mature, which involves pollination and the seeds filling out. This maturation process generally takes an additional four to six weeks after the bloom is fully visible.
The grain harvest is approaching when the large seed head begins to dry, change color, and the seeds become firm. A common field test involves gently rubbing a portion of the flower head between the hands; if the small, golden seeds readily fall out, the plant is ready for harvest. Waiting too long can lead to seed shatter, where the mature seeds drop naturally to the ground.