Planting the Future

WISE OLD PLANTS

ROBYN KLEIN

We easily accept the fact that a tree might be hundreds of years old. But discovering that a wild herbaceous plant can grow for forty or even three hundred years is quite a surprise to most people. Take, for example, the case of green gentian. Peterson’s Field Guide to the Rocky Mountain Wildflowers lists green gentian (Frasera speciosa) as a biennial. Biennials develop a rosette of leaves in their first year or two, and then produce a large flowering stalk with thousands of seeds the following year, after which the whole plant dies. Herbalists in the western United States consider F. speciosa a good digestive-bitters substitute for yellow gentian (Gentiana lutea), which is the European species commonly found on the herb market.¹

What is new and disturbing information, however, is that green gentian is not a biennial at all, but a perennial that has been estimated by some biologists to remain in the rosette stage for up to sixty years.² That herbalists have been unwittingly harvesting these very old roots suddenly presents the possibility that other wild herbs are likewise much older than we have realized. Such discoveries could be crucial to determining sustainable harvesting methods.

OTHER GROWTH-PATTERN FACTORS

Yet it is not just the potential age of these wild herbs that is of importance. Plants are intricately attached to a web of life that can falter or shift for many reasons. Among those factors is the question of how many years a plant takes to become a reproductive individual.

Biologist Ellen O’Callaghan has studied the reproduction of the glacier lily in Colorado. Erythronium grandiflorum is a long-lived perennial found at various altitudes from British Columbia to California to Colorado. This species spends its first five to six years as a nonflowering juvenile with only one or two leaves. It then produces a flower (and seeds) at around year seven. Adult plants, which usually have two leaves of unequal size, have been known to revert back to the nonflowering stage for a year or more.³ Thus, we don’t know the full life span of the glacier lily, but we do know that mature individuals are at least seven to ten years old. This information is important because it suggests that other medicinal genera related to the glacier lily, such as Trillium, Chamaelirium, Aletris, and Lilium, may have similar growth stages. So in estimating their ages, we must consider that they, too, may revert to a nonflowering stage when conditions require conservation of energy and resources.

Other characteristics of perennial plants are important in considering their ability to withstand continued harvest. Paulette Bierzychudek has studied the jack-in-the-pulpit (Arisaema triphyllum), a long-lived perennial that changes sex during its life. This ability to change sex throws off all calculations when we’re trying to decipher whether seeding individuals exist in a population!⁴

Lady’s slippers also have a complex life cycle that includes several stages of below-ground growth that are difficult to assess in the field. Anecdotal accounts from greenhouse experiments have shown that it takes fifteen years to grow an adult, reproductive plant from seeds. Though the life span of these herbs is difficult to ascertain, some biologists estimate that some grow for thirty-nine years.⁵

Not all herbaceous plants reproduce primarily from seeds. Many reproduce predominantly from underground root systems, which create new individual plants that are each exact genetic replicas of the parent. Individuals that sprout from clonal rhizomes and produce leaves are called ramets, while the root system itself is called the garnet. Rhizomes may connect all the individual plants in this clonal population, or sometimes the underground connection dies and rots, leaving an individual separate. Such underground clonal root systems can live for a very, very long time. Thus, most of the oldest plants known are clonal species.

For instance, the largest living organisms in the world are quaking aspens, which have been estimated to be more than one million years old!⁶ Many of the oldest species known are herbaceous plants. One chaparral organism living near the Colorado River has been carbon-dated at ninety-four hundred years old.⁷

Yet age determination for clonal plants can be very complicated. This is because this type of root system moves and intermingles so much that it is difficult to follow the genetic material. Thus, many biologists consider clonal species to be problematic in figuring age. As a result, they tend to ignore them as chosen specimens in life-span research.⁸ Unfortunately, this means that there is a lack of life-history information for clonal plants, many of which have a history of medicinal use.

Cain and Damman studied the medicinal wild ginger (Asarum canadense), which grows from clonal root systems. They discovered that the underground roots that connect the individual plants persist for up to ten years.⁹

HARVEST OF MATURE INDIVIDUALS

Still other population biology factors become very important once we understand their implications. Consider, for instance, that many wildcrafters collect the largest (and thus the most mature) individuals, because the heavier weight brings more income. It is usually assumed that the smaller, juvenile plants within a harvested population will continue to survive or that enough seeds will already be present in the soil to maintain a healthy population. However, myriad crucial environmental and biological factors can alter this utopian attitude.

Take, for example, the pink lady’s slipper, (Cypripedium acaule). Observational research indicates that individuals in the seed and seedling stages (ending at around the fourth year of growth) have a very high mortality.¹⁰ That is, many juveniles do not survive to reproductive age at all. Harvesting older plants—which are therefore the most successful survivors, with the strongest genes—results in less of these individuals in the population. This practice may likely lead to a disproportionately large number of smaller plants. If these do manage to survive and produce seeds, they may produce more plants with less robust genes. The results of harvesting older individuals from a population may not be evident for decades. Perhaps there is a very good reason for the herbalists’ adage, Leave the grandmother plants.

THE UNITED PLANT SAVERS LISTS

Let us now consider the particular species found on the United Plant Savers At-Risk and To-Watch Lists. At risk is defined as “those herbs broadly used in commerce that are—due to factors such as loss of habitat and overharvest—diminishing in population and viability within their current ranges.” Table 1 lists crucial facts about these species.

From this table you can see that 82 percent of the species listed are treasured for their roots or rhizomes. Thus harvest destroys not only the individual, but also the seeds these plants would have produced for many years to come. Notably, most are perennials and not in mass cultivation—an option that would reduce the pressure on their wild populations. Species on this list are from an assortment of plant families with myriad evolutionary strategies and growth characteristics.

A second category of plant species has been compiled by United Plant Savers that may not fit into the at-risk category but are still worthy of closer scrutiny due to their popularity in some instances. Assessment of whether these species should be added to the At-Risk List would be greatly enhanced if we considered not only the part of the plant collected, but also the plants’ age at reproductive maturity and their possible life span.

You can see from table 2 that roots are still the highly valued part of the herbs. Most of these species are perennial, and most are not in cultivation. Again, these species represent many diverse plant families. In fact, it is apparent from both the lists that medicinal plant species most in danger are those that are perennial, whose roots are collected, and for which cultivation is difficult or uncommon.

The important information missing from these lists is the estimated life spans of these species. But first, how do biologists estimate the life spans of plants?

GROWTH STAGES

Plants cannot be carbon-dated unless they are hundreds of years old. But aging an individual can be accomplished by simply observing its growth stages and how many years it stays in these stages. Much of this research involves complicated mathematical analysis that is impractical for laypeople. However, close estimates can be accomplished through simpler means.

For example, you might select plots that can be revisited for at least five years. Individual plants in these plots can be measured and tagged. From this a number of growth stages can be ascertained by noting the unique characteristics and sizes of the individuals. For example, a juvenile with one leaf would be in a younger growth stage than a juvenile with two leaves, and so on. Once the stages are ascertained, then it is a matter of recording how many years an individual stays in that growth stage. Finally, you can add up the number of years spent in each growth stage to estimate the minimum age of a mature individual. The difficulty, of course, is in estimating the age of mature individuals. But this is still possible with continued observation over a period of many years or decades.

Biologists Margaret E. Cochran and Stephen Ellner have calculated many plant ages using the growth-stage technique.¹¹ For example, they compared the growth stages of two plants—a perennial weedy species called teasel (Dipsacus sylvestris) and the wild and delicate pink lady’s slipper (Cypripedium acaule), both of which reproduce by seeds. Table 3 compares their growth stages.

Dipsacus must grow for six years and Cypripedium for eight years before developing the first flowers and seeds. This is much longer than it takes to get a college education!

Herbalists and wildcrafters need not be mathematical geniuses to estimate the growth stages and ages of hundreds of long-lived perennial plants. It takes only the dedication of at least five years to record sizes of various individual plants in more than several plots to get some fair estimates.

Though how long a plant species stays in a growth class is not always known, we can sometimes find information on the number of growth stages known for a species. Table 4 offers growth-stage information that could be used to estimate life spans of some wild medicinal herbs.

COUNTING RINGS AND LEAF SCARS

Other simple ways to determine the ages of long-lived perennials include counting leaf scars. Estimating the age of a ginseng (Panax spp.) root is a tradition going back thousands of years. This technique should also work well for members of the Lily family, such as trillium and helonias.

Annual rings can be counted in a cross section of a root. Dietz and Ullmann published a list of wild plants for which ring counting is or is not a viable technique.¹² For example, the growth rings found in comfrey roots (Symphytum officinale) and horseradish are clear and easy to read. However, the growth rings in the roots of mugwort (Artemisia vulgaris), chicory (Cichorium intybus), and snakeroot (Eryngium campestre) are only weakly readable. Thus, this technique is applicable to some plant families but not others.

In reviewing the population biology literature, one very important plant family is absent—the Parsley family (Apiaceae or Umbelliferae). The ages of important wild medicinal plants, such as osha (Ligusticum spp.) and biscuit root (Lomatium dissectum), are not known. But while the rings of the roots in these species are all but nonexistent, the leaf scars are quite evident.

One species of osha, Ligusticum filicinum, common in parts of the Rocky Mountains provides a clue. The root of one small specimen, measuring ½ inch in diameter, 8 inches long, and weighing approximately 0.4 ounce, evidenced more than eighteen leaf scars. Even considering that one year’s growth might be represented by up to three leaf scars, this example still suggests that larger specimens are at least ten years old, and probably much, much older. It is folly to assume that continued digging of wild osha and Lomatium root is a practice without finite limits.

LIFE SPANS OF SOME PERENNIAL PLANTS

The known estimated life spans of more than fifty species could be very useful in determining the ages of our wild medicinal herbs. Table 5 provides a compilation of the estimated life spans found in the literature.

These estimated ages suddenly make us recognize that many of the medicinal plants being harvested from the wild are most likely very old. How many individuals should we harvest from a population? How soon could that population return to its current size? Thoughtful consideration of the life spans of our medicinal herbs should change our appreciation of them. It should also change the way we harvest them.

We can use this information to make valuable decisions. For instance, from this list we might deduce that many perennials in the Lily family tend to be long lived; populations of any lily species should thus be carefully managed. The presence of helonias (Chamaelirium luteum), trillium (Trillium spp.), and true unicorn (Aletris farinosa) on the UpS At-Risk List therefore should not be surprising. Collection of the underground parts of these species may, in fact, irreparably damage a population that cannot rebound when future seeds are removed. Remember that a plant in the Lily family does not form a flower for some seven to ten years. And we cannot assume that reseeding will occur. Research shows that the disappearance of genetic material and the lack of food (nectar) available to pollinators can both have a great impact on a plant population’s ability to survive. If the flowering individuals in a population become too sparse, the pollinators may not be able to find enough plants to cross-pollinate any of them.¹³

Herbalists and wildcrafters have not traditionally considered issues of reproductive cost, stage-structured models, and life demographics. This is the territory of academia, with unfamiliar technological terms and rather daunting mathematical equations. But we must bravely delve into these issues if we are to discover facts crucial to the continuance of our wild medicinal herbs.

ESTIMATING AGES FOR HERBS

Between 1995 and 1998 some seven to ten thousand pounds per week of dried Echinacea angustifolia was shipped out of eastern Montana to feed a growing U.S. and international demand.¹⁴ Very little is understood about how such massive harvesting affects these wild populations.

Another wild medicinal plant used in herbal medicine, though not as commonly, is Balsamorhiza sagittata, or arrow-leaved balsamroot. It, too, exists only in locally abundant populations. Very little is known about the growth stages and life spans of either species. There are no recorded estimated ages for Echinacea or Balsamorhiza.

But perhaps we can make use of the published estimated ages for related plants. Both species are from the Aster (Compositae or Asteraceae) family. Various species in the Aster family have been aged at eleven, nineteen, and forty years (Centaurea maculosa, Liatris cylindracea, and Helianthella quinquenervis, respectively). Therefore, could we not estimate that the oldest Echinacea individuals are in excess of twenty years of age? In comparison, the very stout and much larger taproot of a mature B. sagittata must surely be between forty and eighty years old.

Lomatium dissectum is another wild herb that has a questionable ability to meet the demands of the world’s herbal market. Estimating its age is a little more problematic, since age estimations for species in the Parsley (Apiaceae) family are lacking in the literature. However, the Parsley family is very closely related to the Ginseng (Araliaceae) family¹⁵ Therefore, the fact that Aralia spp. can grow to be thirty years of age and Panax spp. can grow to fifty or sixty should offer us some guidance. It would be conservative to suggest that mature L. dissectum individuals in stable populations are most likely between twenty and forty years old—especially considering that dried sliced roots found on the market are often 3 inches in diameter.

CONCLUSION

It should now be clear that any herb whose roots are highly prized on the herbal market is potentially at risk if it is a long-lived perennial harvested primarily from the wild. Efforts to encourage sustainable harvesting practices and to protect these valuable resources must continue. If we do nothing, we can expect that many other wild medicinal herbs will fall into a decline similar to that of the rare sixty-year-old ginseng root—something only our grandparents now remember.

ACKNOWLEDGMENTS

I benefited greatly from the many biologists who helped me locate information—especially Joan Maloof and David W. Inouye, who unwittingly started this quest. And of course Frasera speciosa, whose patience and determination have not gone unnoticed.

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