A Flower that Opens after 7 years and lasts for 7 days

12/10/2023

Usually, the life cycle of most plants and crops lasts for 6 months and they flower within weeks. But there is a plant genus in the sunflower family (Asteraceae) known as Argyroxiphium. Its members are known by the common names Silver Sword or Green Sword due to their long, narrow leaves and silvery hairs in some species.

It belongs to a larger radiation of over 50 species, including physically different genera Dubautia and Wikesia This grouping is often referred to as the silver sword alliance. Botanist P.H. Raven referred to this radiation as “the best example of adaptive radiation in Plants.

The majority of plants and crops typically have a life cycle lasting about 6 months and can flower in just a few weeks. However, there is a plant genus within the Asteraceae family, known as Argyoxiphium, which is commonly called the Sliver Sword or Green Sword due to its distinctive long, slender leaves and the presence of silvery hairs on certain species. Argyroxiphium is part of a larger group of plants consisting of over 50 species, including other genera like Dubautia and Wikesia. This collection of plants is often referred to as the Silver Sword Alliance. Botanist P.H. Raven once described this group as “the most notable example of adaptive radiation in the plant kingdom.”

The Possibility of Extension

Maui’s silverswords (Argyroxiphium sandwicense subsp. macrocephalum) had been declining for centuries, victims of feral goats and tourist’s eager to uproot living souvenirs. Even before the silversword was declared a federally threatened species in 1992, conservationists had fenced the barren slopes of their habitat, rid the area of goats, and planted silversword seeds. The efforts seemed to be working until the 1990s, after which the Maui species declined by 60%. Plants that sit farther down the volcano have suffered the most, even though they live in wetter conditions. 

In 2016, Paul Krushelnycky, an ecologist at the University of Hawaii in Honolulu, noted that this recent drop coincided with more frequent changes in the trade winds, east-to-west winds that flow up the volcano. Increasingly, the trade winds’ cool, moist air has been trapped midslope by warmer air, creating hotter, drier conditions for the uphill plants. Such inversions have always been common, Krushelnycky notes, but now they are even more frequent, likely because of climate change.


To understand why silverswords at lower elevations are the most vulnerable, Krushelnycky and his colleagues grew seeds taken from plants living at low, medium, and high elevations in greenhouses and small outdoor plots. They watered some of them regularly and some of them irregularly, to compare growth under different conditions. They also measured how many plants survived. The researchers thought that plants from the highest elevations—where conditions were driest—would do better in the artificial “drought” scenarios, thanks to their presumed adaptations to dry living.

Seeds planted at lower elevations and subjected initially to moist conditions were the least likely to survive later droughts, regardless of which plants the seeds came from, the team reports in Ecological Monographs. “This suggests that traits acquired in response to the wetter growing conditions, not genetic differences, made them less drought resistant,” Krushelnycky says. Many researchers worry that increasing fluctuations in climate conditions can have a detrimental effect on ecosystems, says Bruce Baldwin, a botanist at the University of California, Berkeley, who was not involved with the work. But that “can be difficult to demonstrate convincingly,” he says. The new findings, he adds, show that Silver Swords’ early adaptations to their environments “can later work against them.”

Rather than transplanting Silver Swords from high elevations—where conditions are harsher— to lower ones, Krushelnycky says it may be more productive to transplant them to places with more consistent moisture, like lower grade slopes. Toward that end, he and his colleagues are planting Silver Swords in a wide variety of habitats to see which are best.