A sometimes mysterious and much underappreciated plant family – grass. We eat it, weave it, build with it, wear it, make fuel out of it, livestock depend on it, it blankets lawns and playing fields, holds roadsides and hills in place, serves as winter cover crop in agriculture, and waves about in the prairie breeze providing bison food, grassland bird nesting habitat, and forage for the many small creatures that feed predators – wolves, coyotes, eagles, and bears.
What’s a Grass?
Grasses are all in the family Poaceae and are set apart from similar-looking plants by having a hollow stem. The rhyme goes: sedges have edges, rushes are round, and grasses like asses have holes in their stems. Patrick Elvander taught me that- he was an inspirational botany professor at UCSC who died too young. That rhyme deserves some decoding. Sedges mostly have triangular stems and leaves, with 3 edges to their leaf blades. Most rushes have round leaves and stems, both are solid, filled with a pith. Grasses have hollow stems like a straw.
There are more than 500 species of grass in California; around half are introduced. There are more than 200 varieties of grass in Santa Cruz County, so there’s lots to learn locally just with this group of plants!
Food from Grass
Corn, rice, sorghum, barley, wheat, oats, and rye are the commonly known human food grasses. You might have a hard time telling barley, wheat, oats, and rye seeds apart when they are whole…but corn, woa- what a different looking seed! Corn is a New World grass, the others are from the other side of the world. Rice is pretty different looking (New World wild “rice” isn’t related). Each of these grasses has distinct flavors.
Grain species have been bred into varieties for different uses. For example, corn has varieties divided into: flint, flour, dent, pop, sweet, and waxy. Wheat has seven such varieties. And so on.
Native peoples ate native grasses, but we’re not sure all of the ones they used. European wild oats spread so quickly that when Old World ethnographers first encountered native peoples in northern California, they had already incorporated them in their dietary repertoire.
Holding the Soil in Place
Beyond food, grasses are useful for soil conservation. Have you ever stood in a parking lot or listened to the rain on a roof during a rainstorm? It is noisy! That same heavy downpour falling on a grassland is quiet. The flexible grass blades intercept raindrops, lowering them gently to the ground, springing back up to catch the next one. If the rain is very heavy, the soaked blades fall over, protecting the soil.
People have long appreciated the erosion control utility of grasses around California. In Santa Cruz County, there was for a time a specific County-government mandated erosion control seed mix that was mostly grass seed. Alas, the well-meaning County had prescribed a host of species that were non-native and quite invasive, so I’m hoping no one uses it anymore. At about that same time a similarly poor policy was widely implemented across the state: seeding nonnative invasive annual rye grass seed after wildfires. There was concern about the species’ invasiveness, but the practice was only halted after scientists documented slope failure caused by the unnaturally weighty grass biomass and increased fire danger from tons of fine, flammable dead grass the next summer.
You probably know many interesting and useful grasses: lemon grass for Thai cooking and bamboo for stir frying new shoots and use of older shoots for plant stakes and buildings. A local woodland species, vanilla grass, has been grown in plantations for the flavoring of pipe tobacco. Many species have been woven into baskets. Broom corn, a type of millet, makes natural brooms and some midwestern towns were economically supported by this industry in the early 1900’s.
Then there is chicken scratch, cattle and horse pasture, silage for dairies, grains in the feedlots, and bales of hay in the barn: the many ways that grasses feed livestock.
Not all grasses are welcomed by livestock. Interestingly, a terribly invasive toxic perennial grass is being sold for seeding horse pastures: tall fescue. This grass easily gets infected by a fungus that is mutagenic and causes horses to miscarry! And, people seed pastures with rye grass despite its tendency to mold and cause something called ‘the staggers’ with poisoned livestock wandering around like they are drunk, losing weight and seeming quite sick.
Besides some species poisoning horses and cattle, other grasses have been bad problems. Some suggest that the collapse of the Mayan civilization was due to the invasion of their agricultural systems by uncontrollable weedy grasses (and drought). Modern agriculture is also plagued by grassy weeds. Some were enthusiastic about using herbicides for grass weeds and even genetically engineering the crops to be resistant to herbicides. Very soon, strains of Italian ryegrass became resistant to herbicides and the presence of that species on farms vastly devalued the resale value of the land.
Italian ryegrass has more notoriety: it is the most allergen filled plant known to humankind. The species proliferates with the nitrogen raining down from air pollution, and so lines highways and takes over meadows around the Bay Area. When it blossoms, everyone gets sick- even people who don’t know they have grass allergies report sore throats and coughing for the 2 weeks of its peak bloom. So, invasive non-native grasses are a health hazard – and grassland restoration and management is important for human health.
Walk in a California grassland and 80% of what you step on is non-native, mostly invasive grasses. Each year, new invasive species show up in the grasslands introduced accidently through global trade or purposefully through the nursery or turf grass industries. Once naturalized, new species evolve to become better fit and can be even more invasive.
Did you know that bunchgrasses move around? Many of our native perennial grasses are called bunchgrasses because they grow in clumps, without runners. And yet, the stems of each clump might die on one side and new ones might sprout on the other side, so the grass clump can move around. Long term studies have monitored meters of movement in bunchgrasses over decades.
Soil Carbon and Perennial Grasses
There has been a lot of bogus hand-waving about the differences between native perennial grasses vs. non-native annual grasses. I have been hearing a lot recently that native perennial grasses have much more extensive, deep, carbon-storing root systems in contrast to exotic annual grasses. These distinctions miss the troubling invasion of non-native perennial grasses into our coastal prairies…some of those species are more robust than native perennials. Also, native perennial grasses come in many sizes with many different morphologies- some are teeny tiny (Blasedale’s bent grass, an endangered grass of Santa Cruz’ North Coast), others are very medium sized (meadow barley). I would wager that an annual exotic oat grass on rich soil would have a larger root system and sequester more carbon than the native perennial meadow barley growing alongside it.
This hand waving seems to me to be unnecessary jingoism for soil carbon sequestration via restoration of a very few species of big, burly native bunchgrasses. This is dangerous because our prairies are so much more rich than those few species of large, common native perennial grasses. Planting/stewarding just a few native grasses will cost us a wealth of other species diversity and potentially the resilience of the prairie ecosystem as a whole.
-this article originally appeared in Bruce Bratton’s BrattonOnline.com blog.