Photo by BlueRidgeKitties licensed under CC BY-ND 2.0.
Star chickweed (Stellaria pubera) has been called North America’s showiest chickweed and I am inclined to agree. Come mid-spring, this lovely woodland plant produces wonderful white flowers that measure about 1/2 inch across and are ringed by five petals so deeply notched that there appear to be ten. Star chickweed’s floral display takes place rather close to the ground on small, fuzzy shoots but as the flowering window for this species begins to close, a change takes place within the plant. By mid-summer, star chickweed will have grown into something completely different.
As mentioned, flowering for star chickweed occurs close to the ground. During this time, its stems don’t elongate more than a few inches and its leaves are broad, blunt, and sessile. Once seed has been set, star chickweed goes through another growth spurt. New stems begin to grow that are much more vigorous in nature than the flowering shoots. They sprout up from the base of the plant and completely over-top spring growth. They can reach heights of nearly 12 inches and produce much thinner leaves. These summer shoots are usually sterile and only in rare instances have flowers been reported.
![Star chickweed showing low-growing fertile shoots (front) and taller, sterile shoots (back). [SOURCE]](https://images.squarespace-cdn.com/content/v1/544591e6e4b0135285aeb5b6/1589231950907-7YGTJJT7TSVAXG9SYFLO/IMG_0762.JPG)
Star chickweed showing low-growing fertile shoots (front) and taller, sterile shoots (back). [SOURCE]
Star chickweed’s shape-shifting abilities have confused many a botanizer over the last century or so. Because the fertile and sterile shoots look completely different from each other and largely occur at different times of the growing season, some early botanists even went as far as to describe them as different species. Why this plant goes through two distinct growth phases is still something of a mystery but I suspect it has a lot to do with energy reserves.
Perhaps star chickweed has evolved this shape-shifting habit to keep up with changes in surrounding vegetation. Early in the year, the tree canopy above hasn’t completely closed and many of its herbaceous neighbors are still putting on growth of their own. As such, star chickweed probably doesn’t experience as much competition for light early in the season. Of course, conditions on the forest floor change drastically as spring gives way to summer. It could be that the taller, more vigorous sterile shoots are better able to compete for light as the forest fills in around star chickweed.
Another mystery that still has yet to be answered is what triggers the change in growth. A study published back in 1942 concluded changing day length alone could not explain it and suggested it may be in response to rising summer temperatures. However, their experiment was not terribly thorough, leaving such conclusions in the realm of speculation. I kind of like that about nature. There is always a new mystery to uncover, always a deeper understanding to gain.