Almost too fantastical to be terrestrial, youth-on-age, or, piggyback plant (Tolmiea menziesii) is one of Cascadia’s most unusual wildflowers. In moist environments, it is abundant in the forest floor mosaic, yet easily goes unnoticed, its tiny blooms in muted tones receding into the woodland shadows and belying its fascinating life cycle and evolutionary history.
Blooms
On close inspection, each extraordinary flower of youth-on-age consists of five sepals that form a flaring calyx1A calyx is the outer structure that encloses or forms the base of a flower. It is composed of the sepals, which are modified leaves that enclose a flower bud before it opens., four tendril-like petals that curl from its jutting maw like the whiskers of a dragon, three prominent stamens2A stamen is the male reproductive structure of a flower, consisting of an anther in which pollen is produced and usually a slender filament that attaches it to the flower. An individual flower typically has many stamens., and two translucent styles3A style is a typically slender structure that connects a stigma, which receives pollen, to the ovary, where seeds develop, the three components constituting the pistil, a plant’s female reproductive structure.. Their color ranges from chartreuse through maroon to brown. Each bloom is barely a half inch/1.50 centimeters long, but joins a raceme, or, unbranched flower spike of up to fifty others reaching nearly three feet/one meter high.
Reproduction
As if the alien-like flowers weren’t strange enough, they are followed by curious, arrowheaded seed capsules protruding from the husks of the blossoms that bore them. However, youth-on-age’s unusual characteristics don’t stop there. Not only does this prodigious plant procreate conventionally by seed, it also reproduces asexually by sprouting new plantlets directly from where its leaves join their petioles, or, leaf stems. As the maturing leaves fan downward and touch the ground, the plantlets root. Hence, both the common names “youth-on-age” and “piggyback plant.” Underground, this perennial plant also spreads by rhizomes, subterranean stems that produce roots below and new shoots above. By this combination of sexual and asexual methods of reproduction, youth-on-age forms a loose groundcover in shady conditions where it has an ecological advantage, but also joins others in mixed understory communities.
Similar Species
When not in bloom, youth-on-age’s fuzzy, palmate leaves can look confusingly similar to those of the distantly related fringecup (Tellima grandiflora). To distinguish them, look for tiny offsets or buds in the leaf bases where they join the petioles. They will only be present in youth-on-age and begin to form in late spring and early summer. The tips of youth-on-age’s leaf lobes also tend to be slightly more pointed than those of the fringecup. Also check the leaves and petioles on the upper stem. Youth-on-age’s upper leaves will be smaller with shorter petioles, but never clasping, as with the fringecup‘s stemless upper leaves. Finally, the youth-on-age’s seed capsules are triangular and dangling, much unlike the upturned bowls of the fringecup.
Botanists have recently discovered that some youth-on-age in Oregon and California have only two sets of chromosomes, rather than four as in the broader population. (Unlike species in the Animal Kingdom, plants are much more capable of possessing and even thriving with as few as one to as many as several sets of chromosomes.) The diploid (having two sets of chromosomes) population of youth-on-age has been reclassified as a separate species, Tolmiea diplomenziesii, commonly named the southern piggyback plant. Although visually quite similar to T. menziesii, it can be differentiated by its smaller overall size, more elongated leaves, and lesser propensity for asexual reproduction through leaf-borne plantlets. Fascinatingly, T. diplomenziesii is considered the original species, which means that, at some point in its evolutionary history, it produced mutated offspring with twice the chromosome count. Those added chromosomes appear to have resulted in a more robust lineage that was able spread north into cooler habitat and reproduce more readily by foliar offsets, becoming the dominant species in a broader range.
Range and Habitat
Look for T. menziesii blooming in late spring and early summer. It favors mixed coastal and riverine woodlands at low to mid-elevation from southern Alaska through northern California, as in the accompanying habitat photo where many of the specimens featured on this page were photographed. In Western Washington, it is commonly found in the company of the fringecup and the largeleaf avens (Geum macrophyllum).
Gallery
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