The thing about Narrow-leaved waterwillow, Justicia angusta, is that it isn’t a willow at all. It’s not a tree. It’s not a shrub. At best, it might get a foot or so off the ground, and it’s actually related to wild petunias.
But it does have narrow leaves. Extremely narrow leaves, as a matter fact.
It’s a Florida native, found throughout the Peninsula, parts of the Panhandle but not the Keys. Its range extends into two counties in southeastern Georgia. Delray Beach-based Institute for Regional Conservation considers narrow-leaved waterwillow rare within South Florida, but it really isn’t common anywhere. Georgia considers it critically imperiled.
It is a perennial, multi-stemmed plant that stands eight to 12 inches tall, but it can be taller when growing in standing water. Leaves are arranged alternately along the stem and widely separated from each other; the blades are long and narrow, eight times as long as they are wide. The leaves also have hard mineral deposits called cystoliths along the midvein, which probably evolved to discourage critters from munching on them. After all, who wants a stone in their salad? Cystoliths are a feature of Acanthaceae, the family of which narrow-leaved water-willow is a member.
The most outstanding physical feature of narrow-leaved waterwillow are the unusually shaped flowers, which come in pink to lavender to purple. They have two lips, an upper that’s notched and three lower with three lobes that spread outward. There’s a nector path in the center that leads pollinators to the throat. It both self- and cross pollinates. The fruit is a capsule that contains four seeds; when ripe the capsule “explodes,” shooting the seeds away from the parent plant.
Narrow-leaved waterwillow goes dormant in the winter, but sends up shoots in early spring. Flowers bloom spring and summer.
Narrow-leaved waterwillow is found where there’s wet to moist soils, in marshes and wet prairies, and with full sun or part shade. It will take standing water for a time; it cannot tolerate saltwater or salt spray, and it cannot tolerate drought.
Small bees and butterflies are pollinators, as are hummingbirds. The phaon crescent butterfly probably uses the plant as a host. Look closely toward the bottom left on the photo above, and you'll see two phaon crescents.
The name of genus, by the way, honors James Justice, an 18th century Scottish horticulturalist and gardener.
Other common names for the plant: Everglades water-willow and pineland water-willow. Narrow-leaved waterwillow is a member of Ancantheceae, the family of wild petunias.