Annual bluegrass perennially tenacious

Annual bluegrass possesses both an annual and perennial lifecycle at the same time.


Annual bluegrass

Benjamin Franklin said, “… nothing can be said to be certain, except death and taxes and annual bluegrass.” Of course, he didn’t say that last part, but he might have included the annual bluegrass bit if he knew it grows and thrives on all seven continents. Golf course superintendents have tried to manage or eradicate annual bluegrass, and sometimes both at the same time.

Annual bluegrass has been unofficially categorized as being an “annual biotype” or a “perennial biotype” based on observations from turf managers. We have seen annual bluegrass appear as a lighter shade of green, grow with shallow roots and produce an abundant amount of seed, thus reflecting an annual nature. We have seen annual bluegrass that is darker green in color and finer textured, persists on greens to produce an exceptional putting surface and tolerates those low mowing heights, thus conveying a perennial nature.

The early botanical literature described annual bluegrass as having an annual lifecycle. This unintentional misunderstanding was perpetuated by a sort-of “telephone game” among those early researchers (

So, is annual bluegrass an annual or perennial? The answer: Annual bluegrass possesses both an annual and perennial lifecycle at the same time and, actually, all of the time. David Huff, Ph.D., at Penn State University, led a team of investigators using advanced genetics, bioinformatics and data analysis tools to provide that answer. It’s all about epigenetics — the study of how a plant’s behavior and the environment influence and affect the way their genes work.

Seeds of Poa annua, Poa infirma and Poa supina were germinated on moist filter paper in petri dishes, then transplanted into potting soil and grown in the greenhouse. With each species, root tips were collected and processed in the laboratory to examine chromosomes and learn more about the genetic makeup and history of those plants. Recall from biology class that chromosomes are thread-like structures located inside the nucleus of a cell, and these chromosomes are made of protein and deoxyribonucleic acid (DNA). When living things reproduce, they pass their genes (i.e., DNA) along to their offspring.

This genetic detective work confirmed that Poa annua’s “mom” is Poa infirma (an annual species native to the warmer climate in the Mediterranean region) and its “dad” is Poa supina (a perennial species native to the higher elevation and colder climate of northern Europe). Therefore, annual bluegrass is an allotetraploid species. Wait … what? This means that every cell in every annual bluegrass plant contains the genetic material of two different species (i.e., Poa infirma and Poa supina). So, annual bluegrass is genetically programmed to take after its mom and behave like an annual or follow in its dad’s footsteps and behave as a perennial.

So how does annual bluegrass know when to be an annual or perennial? Annual bluegrass is so well adapted to so many environments and conditions. In fact, annual bluegrass has “transgenerational memory.” Wait … what? Huff’s team grew annual bluegrass plants in the greenhouse and mowed them at putting green height-of-cut. The annual bluegrasses produced seed, and that seed was collected and germinated to produce offspring. Those offspring annual bluegrass plants “remembered” their parents’ mowing height. In other words, the turf management practices influenced the growth habit of those mowed plants, and that growth habit continued to be expressed by the next generation of plants.

Perhaps several hundred thousand years from now, the annual bluegrass genome (both the annual and perennial lifecycle parts contributed by its Poa infirma and Poa supina parents, respectively) will have become fully integrated, and then either the annual or perennial lifecycle will dominate the species. Until then, today’s annual bluegrass contains the ability or “genetic plasticity” to be both an annual and perennial. Ben Franklin would have enjoyed knowing all about this tenacious bluegrass.


  1. Benson, C.W., Q. Mao and D.R. Huff. 2021. Global DNA methylation predicts epigenetic reprogramming and transgenerational plasticity in Poa annua L. Crop Science 61(5):3011-3022 (
  2. Huff, D.R. 2023. Understanding Poa annua. USGA Green Section Record 61(17):108 (

Mike Fidanza, Ph.D., is a professor of plant and soil science in the Division of Science, Berks Campus, at Pennsylvania State University in Reading, Pa. He is a 22-year member of GCSAA.